Inclusive З c production in eЗe annihilations at ББ sp И 10:54 GeV and in Е4SЖ decays

16 Pages·2007·0.57 MB·English

PHYSICALREVIEW D 75, 012003 (2007)
p
Inclusive (cid:1)(cid:1) production in e(cid:1)e(cid:2) annihilationsat (cid:1)s(cid:1)(cid:1) (cid:3) 10:54 GeV andin (cid:2)(cid:4)4S(cid:5) decays
c
B.Aubert,1 M.Bona,1 D.Boutigny,1 F. Couderc,1 Y. Karyotakis,1 J.P. Lees,1 V.Poireau,1V. Tisserand,1 A.Zghiche,1
E. Grauges,2 A.Palano,3 J.C.Chen,4 N.D.Qi,4G.Rong,4 P. Wang,4 Y.S.Zhu,4 G.Eigen,5 I. Ofte,5 B. Stugu,5
G.S.Abrams,6 M.Battaglia,6 D.N.Brown,6J. Button-Shafer,6R.N.Cahn,6 E. Charles,6 M.S.Gill,6Y.Groysman,6
R.G.Jacobsen,6 J.A.Kadyk,6 L.T. Kerth,6 Yu.G.Kolomensky,6 G.Kukartsev,6 G.Lynch,6 L.M.Mir,6 T.J.Orimoto,6
M.Pripstein,6N.A.Roe,6M.T.Ronan,6W.A.Wenzel,6P.del AmoSanchez,7M.Barrett,7K.E. Ford,7T.J.Harrison,7
A.J.Hart,7C.M.Hawkes,7A.T.Watson,7T.Held,8H.Koch,8B.Lewandowski,8M.Pelizaeus,8K.Peters,8T.Schroeder,8
M.Steinke,8 J.T.Boyd,9J.P.Burke,9W.N.Cottingham,9 D.Walker,9D.J.Asgeirsson,10 T. Cuhadar-Donszelmann,10
B.G.Fulsom,10 C. Hearty,10 N.S. Knecht,10T.S. Mattison,10 J.A.McKenna,10 A.Khan,11 P. Kyberd,11 M.Saleem,11
D.J. Sherwood,11 L. Teodorescu,11V.E. Blinov,12 A.D. Bukin,12 V.P.Druzhinin,12 V.B. Golubev,12 A.P.Onuchin,12
S.I. Serednyakov,12 Yu.I. Skovpen,12 E.P. Solodov,12 K.Yu Todyshev,12 M.Bondioli,13 M.Bruinsma,13M.Chao,13
S.Curry,13 I. Eschrich,13 D.Kirkby,13 A.J. Lankford,13 P. Lund,13 M.Mandelkern,13R.K.Mommsen,13 W.Roethel,13
D.P.Stoker,13S.Abachi,14C.Buchanan,14S.D.Foulkes,15J.W.Gary,15O.Long,15B.C.Shen,15K.Wang,15L.Zhang,15
H.K.Hadavand,16E.J.Hill,16H.P.Paar,16S.Rahatlou,16V.Sharma,16J.W.Berryhill,17C.Campagnari,17A.Cunha,17
B.Dahmes,17T.M.Hong,17D.Kovalskyi,17J.D.Richman,17T.W.Beck,18A.M.Eisner,18C.J.Flacco,18C.A.Heusch,18
J.Kroseberg,18W.S.Lockman,18G.Nesom,18T.Schalk,18B.A.Schumm,18A.Seiden,18P.Spradlin,18D.C.Williams,18
M.G.Wilson,18J.Albert,19E.Chen,19A.Dvoretskii,19F.Fang,19D.G.Hitlin,19I.Narsky,19T.Piatenko,19F.C.Porter,19
A.Ryd,19 G.Mancinelli,20 B.T. Meadows,20K. Mishra,20 M.D.Sokoloff,20 F. Blanc,21 P.C. Bloom,21 S.Chen,21
W.T. Ford,21 J.F.Hirschauer,21 A.Kreisel,21 M.Nagel,21 U.Nauenberg,21 A.Olivas,21 W.O.Ruddick,21 J.G.Smith,21
K.A.Ulmer,21 S.R.Wagner,21 J.Zhang,21 A.Chen,22 E.A.Eckhart,22 A.Soffer,22 W.H.Toki,22 R.J. Wilson,22
F.Winklmeier,22 Q.Zeng,22 D.D. Altenburg,23E. Feltresi,23 A.Hauke,23 H.Jasper,23 J. Merkel,23 A.Petzold,23
B.Spaan,23 T. Brandt,24 V. Klose,24 H.M.Lacker,24 W.F.Mader,24 R. Nogowski,24J. Schubert,24 K.R. Schubert,24
R.Schwierz,24J.E.Sundermann,24A.Volk,24D.Bernard,25G.R.Bonneaud,25E.Latour,25Ch.Thiebaux,25M.Verderi,25
P.J.Clark,26W.Gradl,26F.Muheim,26S.Playfer,26A.I.Robertson,26Y.Xie,26M.Andreotti,27D.Bettoni,27C.Bozzi,27
R.Calabrese,27 G.Cibinetto,27 E. Luppi,27 M.Negrini,27 A.Petrella,27 L. Piemontese,27 E. Prencipe,27 F. Anulli,28
R. Baldini-Ferroli,28 A.Calcaterra,28 R. de Sangro,28 G.Finocchiaro,28S. Pacetti,28 P. Patteri,28 I.M.Peruzzi,28,*
M.Piccolo,28 M.Rama,28 A.Zallo,28A. Buzzo,29 R.Contri,29 M.Lo Vetere,29 M.M.Macri,29 M.R. Monge,29
S. Passaggio,29 C.Patrignani,29 E. Robutti,29 A.Santroni,29 S.Tosi,29 G.Brandenburg,30 K.S. Chaisanguanthum,30
M.Morii,30J.Wu,30R.S.Dubitzky,31J.Marks,31S.Schenk,31U.Uwer,31D.J.Bard,32W.Bhimji,32D.A.Bowerman,32
P.D.Dauncey,32 U.Egede,32R.L. Flack,32 J.A.Nash,32 M.B. Nikolich,32 W. Panduro Vazquez,32P.K.Behera,33
X.Chai,33M.J.Charles,33U.Mallik,33N.T.Meyer,33V.Ziegler,33J.Cochran,34H.B.Crawley,34L.Dong,34V.Eyges,34
W.T. Meyer,34 S. Prell,34 E.I. Rosenberg,34 A.E. Rubin,34 A.V. Gritsan,35 A.G.Denig,36 M.Fritsch,36 G.Schott,36
N.Arnaud,37M.Davier,37G.Grosdidier,37A.Ho¨cker,37F.LeDiberder,37V.Lepeltier,37A.M.Lutz,37A.Oyanguren,37
S.Pruvot,37 S.Rodier,37 P. Roudeau,37M.H. Schune,37 A.Stocchi,37 W.F. Wang,37 G.Wormser,37 C.H.Cheng,38
D.J. Lange,38 D.M.Wright,38 C.A.Chavez,39 I.J. Forster,39 J.R. Fry,39 E. Gabathuler,39 R. Gamet,39 K.A. George,39
D.E. Hutchcroft,39 D.J. Payne,39 K.C. Schofield,39 C.Touramanis,39 A.J. Bevan,40 F. Di Lodovico,40 W. Menges,40
R.Sacco,40 G.Cowan,41 H.U.Flaecher,41 D.A.Hopkins,41 P.S.Jackson,41 T.R.McMahon,41 S. Ricciardi,41
F. Salvatore,41 A.C. Wren,41 D.N.Brown,42 C.L. Davis,42 J.Allison,43 N.R. Barlow,43R.J. Barlow,43 Y.M.Chia,43
C.L.Edgar,43G.D.Lafferty,43M.T.Naisbit,43J.C.Williams,43J.I.Yi,43C.Chen,44W.D.Hulsbergen,44A.Jawahery,44
C.K.Lae,44 D.A. Roberts,44 G.Simi,44 G.Blaylock,45C. Dallapiccola,45 S.S. Hertzbach,45 X.Li,45 T.B.Moore,45
S.Saremi,45 H.Staengle,45 R.Cowan,46 G.Sciolla,46 S.J. Sekula,46 M.Spitznagel,46 F. Taylor,46 R.K.Yamamoto,46
H.Kim,47S.E.Mclachlin,47P.M.Patel,47S.H.Robertson,47A.Lazzaro,48V.Lombardo,48F.Palombo,48J.M.Bauer,49
L.Cremaldi,49V.Eschenburg,49R.Godang,49R.Kroeger,49D.A.Sanders,49D.J.Summers,49H.W.Zhao,49S.Brunet,50
D.Coˆte´,50M.Simard,50P.Taras,50F.B.Viaud,50H.Nicholson,51N.Cavallo,52,†G.DeNardo,52F.Fabozzi,52,†C.Gatto,52
L. Lista,52 D.Monorchio,52 P. Paolucci,52 D.Piccolo,52 C. Sciacca,52 M.A.Baak,53 G.Raven,53 H.L. Snoek,53
C.P. Jessop,54 J.M.LoSecco,54T. Allmendinger,55G. Benelli,55 L.A.Corwin,55 K.K.Gan,55 K.Honscheid,55
D.Hufnagel,55 P.D.Jackson,55H. Kagan,55R. Kass,55 A.M.Rahimi,55J.J. Regensburger,55 R.Ter-Antonyan,55
Q.K.Wong,55 N.L. Blount,56 J.Brau,56R. Frey,56O. Igonkina,56 J.A.Kolb,56 M.Lu,56 R. Rahmat,56 N.B.Sinev,56
D.Strom,56 J. Strube,56 E. Torrence,56A. Gaz,57 M.Margoni,57 M.Morandin,57 A.Pompili,57 M.Posocco,57
M.Rotondo,57 F. Simonetto,57 R.Stroili,57 C. Voci,57 M.Benayoun,58 H.Briand,58 J. Chauveau,58 P.David,58
1550-7998=2007=75(1)=012003(16) 012003-1 © 2007 The American Physical Society
B. AUBERTet al. PHYSICALREVIEW D75, 012003 (2007)
L. Del Buono,58 Ch. de la Vaissie`re,58 O.Hamon,58 B.L. Hartfiel,58 Ph.Leruste,58 J. Malcle`s,58J. Ocariz,58 L. Roos,58
G.Therin,58 L. Gladney,59 M.Biasini,60R. Covarelli,60C. Angelini,61 G.Batignani,61 S. Bettarini,61F.Bucci,61
G.Calderini,61 M.Carpinelli,61 R. Cenci,61 F. Forti,61 M.A.Giorgi,61 A.Lusiani,61 G.Marchiori,61 M.A.Mazur,61
M.Morganti,61N.Neri,61E.Paoloni,61G.Rizzo,61J.J.Walsh,61M.Haire,62D.Judd,62D.E.Wagoner,62J.Biesiada,63
N.Danielson,63P. Elmer,63 Y.P.Lau,63 C. Lu,63 J. Olsen,63 A.J.S. Smith,63 A.V.Telnov,63 F. Bellini,64G. Cavoto,64
A.D’Orazio,64 D.del Re,64 E. Di Marco,64 R.Faccini,64F.Ferrarotto,64F.Ferroni,64 M.Gaspero,64 L. Li Gioi,64
M.A.Mazzoni,64 S. Morganti,64 G.Piredda,64 F. Polci,64 F. Safai Tehrani,64 C.Voena,64 M.Ebert,65 H.Schro¨der,65
R.Waldi,65T.Adye,66N.DeGroot,66B.Franek,66E.O.Olaiya,66F.F.Wilson,66R.Aleksan,67S.Emery,67A.Gaidot,67
S.F. Ganzhur,67 G.Hamel de Monchenault,67 W. Kozanecki,67 M.Legendre,67 G.Vasseur,67Ch. Ye`che,67 M.Zito,67
X.R.Chen,68H.Liu,68W.Park,68M.V.Purohit,68J.R.Wilson,68M.T.Allen,69D.Aston,69R.Bartoldus,69P.Bechtle,69
N. Berger,69 R.Claus,69 J.P. Coleman,69 M.R.Convery,69 M.Cristinziani,69 J.C. Dingfelder,69 J.Dorfan,69
G.P. Dubois-Felsmann,69 D.Dujmic,69 W. Dunwoodie,69 R.C.Field,69 T. Glanzman,69 S.J.Gowdy,69 M.T. Graham,69
P. Grenier,69V. Halyo,69 C.Hast,69 T. Hryn’ova,69 W.R. Innes,69 M.H.Kelsey,69 P. Kim,69 D.W.G.S.Leith,69 S.Li,69
S. Luitz,69V. Luth,69 H.L. Lynch,69 D.B. MacFarlane,69 H.Marsiske,69 R.Messner,69D.R.Muller,69 C.P.O’Grady,69
V.E.Ozcan,69A.Perazzo,69M.Perl,69T.Pulliam,69B.N.Ratcliff,69A.Roodman,69A.A.Salnikov,69R.H.Schindler,69
J. Schwiening,69 A.Snyder,69 J. Stelzer,69D. Su,69M.K. Sullivan,69 K.Suzuki,69 S.K. Swain,69 J.M.Thompson,69
J. Va’vra,69 N.van Bakel,69M.Weaver,69 A.J.R. Weinstein,69 W.J. Wisniewski,69 M.Wittgen,69 D.H. Wright,69
A.K.Yarritu,69 K.Yi,69C.C. Young,69 P.R.Burchat,70 A.J. Edwards,70 S.A.Majewski,70 B.A.Petersen,70 C. Roat,70
L. Wilden,70 S.Ahmed,71 M.S.Alam,71 R.Bula,71 J.A.Ernst,71V.Jain,71 B. Pan,71 M.A.Saeed,71 F.R.Wappler,71
S.B. Zain,71 W. Bugg,72 M.Krishnamurthy,72 S.M.Spanier,72 R.Eckmann,73 J.L. Ritchie,73 A.Satpathy,73
C.J.Schilling,73R.F.Schwitters,73J.M.Izen,74X.C.Lou,74S.Ye,74F.Bianchi,75F.Gallo,75D.Gamba,75M.Bomben,76
L. Bosisio,76 C.Cartaro,76 F. Cossutti,76 G.Della Ricca,76 S.Dittongo,76 L. Lanceri,76 L. Vitale,76 V. Azzolini,77
N.Lopez-March,77 F. Martinez-Vidal,77 Sw. Banerjee,78 B.Bhuyan,78 C.M.Brown,78 D.Fortin,78 K.Hamano,78
R.Kowalewski,78 I.M.Nugent,78 J.M.Roney,78 R.J. Sobie,78J.J. Back,79 P.F.Harrison,79 T.E. Latham,79
G.B. Mohanty,79 M.Pappagallo,79 H.R. Band,80X. Chen,80 B. Cheng,80 S.Dasu,80 M.Datta,80K.T. Flood,80
J.J. Hollar,80P.E. Kutter,80 B. Mellado,80 A.Mihalyi,80 Y. Pan,80 M.Pierini,80 R.Prepost,80 S.L. Wu,80
Z. Yu,80and H.Neal81
(BABAR Collaboration)
1Laboratoire de Physique des Particules, IN2P3/CNRS et Universite´ de Savoie, F-74941 Annecy-Le-Vieux, France
2Universitat de Barcelona, Facultat de Fisica, Departament ECM, E-08028 Barcelona, Spain
3Universita` di Bari, Dipartimento di Fisica and INFN, I-70126 Bari, Italy
4Institute of High Energy Physics, Beijing 100039, China
5University of Bergen, Institute of Physics, N-5007 Bergen, Norway
6Lawrence Berkeley National Laboratory and University of California, Berkeley, California 94720, USA
7University of Birmingham, Birmingham,B15 2TT, United Kingdom
8Ruhr Universita¨t Bochum, Institut fu¨r Experimentalphysik 1,D-44780 Bochum, Germany
9University of Bristol, Bristol BS8 1TL,United Kingdom
10University of British Columbia, Vancouver, British Columbia, Canada V6T1Z1
11Brunel University, Uxbridge, Middlesex UB8 3PH, United Kingdom
12Budker Institute of Nuclear Physics, Novosibirsk 630090, Russia
13University of California at Irvine, Irvine, California 92697,USA
14University of California at LosAngeles, LosAngeles, California 90024,USA
15University of California at Riverside, Riverside, California 92521,USA
16University of California at San Diego, LaJolla, California 92093, USA
17University of California at Santa Barbara, Santa Barbara,California 93106, USA
18University of California at Santa Cruz,Institute for Particle Physics, Santa Cruz,California 95064, USA
19California Institute of Technology, Pasadena, California 91125,USA
20University of Cincinnati, Cincinnati, Ohio 45221,USA
21University of Colorado, Boulder, Colorado 80309,USA
22Colorado State University, Fort Collins, Colorado 80523,USA
23Universita¨t Dortmund, Institut fu¨r Physik, D-44221Dortmund,Germany
24Technische Universita¨t Dresden, Institut fu¨rKern- und Teilchenphysik, D-01062 Dresden, Germany
25Laboratoire Leprince-Ringuet, CNRS/IN2P3, Ecole Polytechnique, F-91128 Palaiseau, France
26University of Edinburgh, Edinburgh EH9 3JZ,United Kingdom
012003-2
INCLUSIVE(cid:1)(cid:1) PRODUCTIONINe(cid:1)e(cid:2) ... PHYSICALREVIEW D75, 012003 (2007)
c
27Universita` di Ferrara,Dipartimento di Fisica and INFN, I-44100 Ferrara,Italy
28Laboratori Nazionali di Frascatidell’INFN, I-00044 Frascati, Italy
29Universita` di Genova, Dipartimento di Fisica and INFN, I-16146 Genova, Italy
30Harvard University, Cambridge, Massachusetts 02138, USA
31Universita¨t Heidelberg, Physikalisches Institut, Philosophenweg 12, D-69120 Heidelberg,Germany
32Imperial College London, London,SW7 2AZ, United Kingdom
33University of Iowa, Iowa City, Iowa 52242, USA
34Iowa State University, Ames, Iowa 50011-3160, USA
35JohnsHopkins University, Baltimore, Maryland 21218, USA
36Universita¨t Karlsruhe, Institut fu¨r Experimentelle Kernphysik, D-76021Karlsruhe, Germany
37Laboratoire de l’Acce´le´rateur Line´aire, IN2P3/CNRS et Universite´ Paris-Sud 11,
Centre Scientifique d’Orsay, B.P. 34, F-91898 ORSAY Cedex, France
38Lawrence Livermore National Laboratory, Livermore, California 94550, USA
39University of Liverpool, Liverpool L69 7ZE, United Kingdom
40Queen Mary, University of London, E1 4NS, United Kingdom
41University of London, Royal Holloway and Bedford New College, Egham, Surrey TW20 0EX, United Kingdom
42University of Louisville, Louisville, Kentucky 40292, USA
43University of Manchester, Manchester M13 9PL, United Kingdom
44University of Maryland, College Park, Maryland 20742, USA
45University of Massachusetts, Amherst, Massachusetts 01003,USA
46Massachusetts Institute of Technology, Laboratory for Nuclear Science, Cambridge, Massachusetts 02139, USA
47McGill University, Montre´al, Que´bec, Canada H3A 2T8
48Universita` di Milano, Dipartimento di Fisica and INFN, I-20133 Milano, Italy
49University of Mississippi,University, Mississippi38677, USA
50Universite´ de Montre´al, Physique des Particules, Montre´al, Que´bec, Canada H3C3J7
51Mount Holyoke College, South Hadley, Massachusetts 01075, USA
52Universita` di Napoli Federico II, Dipartimento di Scienze Fisiche and INFN, I-80126,Napoli, Italy
53NIKHEF, National Institute for Nuclear Physics and High Energy Physics, NL-1009 DBAmsterdam,The Netherlands
54University of Notre Dame, Notre Dame,Indiana 46556, USA
55Ohio State University, Columbus, Ohio 43210, USA
56University of Oregon,Eugene, Oregon 97403, USA
57Universita` di Padova, Dipartimento di Fisica and INFN, I-35131 Padova, Italy
58Laboratoire de Physique Nucle´aire et de Hautes Energies, IN2P3/CNRS, Universite´ Pierre et Marie Curie-Paris6,
Universite´ Denis Diderot-Paris7,F-75252 Paris,France
59University of Pennsylvania, Philadelphia, Pennsylvania 19104,USA
60Universita` di Perugia, Dipartimento di Fisica and INFN, I-06100 Perugia, Italy
61Universita` di Pisa, Dipartimento di Fisica, Scuola NormaleSuperiore and INFN, I-56127 Pisa, Italy
62Prairie View A&M University, PrairieView, Texas 77446, USA
63Princeton University, Princeton, New Jersey 08544, USA
64Universita` di Roma LaSapienza, Dipartimento di Fisica andINFN, I-00185 Roma, Italy
65Universita¨t Rostock, D-18051Rostock, Germany
66Rutherford Appleton Laboratory, Chilton, Didcot, Oxon, OX11 0QX, United Kingdom
67DSM/Dapnia, CEA/Saclay, F-91191 Gif-sur-Yvette, France
68University of South Carolina, Columbia, South Carolina 29208, USA
69Stanford Linear Accelerator Center, Stanford,California 94309,USA
70Stanford University, Stanford,California 94305-4060, USA
71State University of New York, Albany, New York 12222, USA
72University of Tennessee, Knoxville, Tennessee 37996, USA
73University of Texas at Austin, Austin, Texas 78712,USA
74University of Texas at Dallas, Richardson,Texas 75083,USA
75Universita` di Torino, Dipartimento di Fisica Sperimentale and INFN, I-10125 Torino, Italy
76Universita` di Trieste, Dipartimento di Fisica and INFN, I-34127 Trieste, Italy
77IFIC, Universitat de Valencia-CSIC, E-46071 Valencia, Spain
78University of Victoria, Victoria, British Columbia, Canada V8W 3P6
79Department of Physics, University of Warwick,Coventry CV4 7AL, United Kingdom
80University of Wisconsin, Madison, Wisconsin 53706, USA
81Yale University, New Haven, Connecticut 06511, USA
*Alsowith Universita` di Perugia, Dipartimento di Fisica, Perugia, Italy
†Alsowith Universita` della Basilicata, Potenza, Italy
012003-3
B. AUBERTet al. PHYSICALREVIEW D75, 012003 (2007)
(Received 5 September 2006; published 9 January 2007)
We present measurements of the total production rates and momentum distributions of the charmed
baryon(cid:1)(cid:1)ine(cid:1)e(cid:2) !hadronsatacenter-of-massenergyof10.54GeVandin(cid:2)(cid:4)4S(cid:5)decays.Inhadronic
c
events at 10.54 GeV, charmed hadrons are almost exclusively leading particles in e(cid:1)e(cid:2) !cc(cid:1) events,
allowingdirectstudiesofc-quarkfragmentation. Wemeasureamomentum distributionfor(cid:1)(cid:1) baryons
c
thatdifferssignificantlyfromthosemeasuredpreviouslyforcharmedmesons.Comparingwithanumber
of models, we find none that can describe the distribution completely. We measure an average scaled
momentumofhx i(cid:3)0:574(cid:6)0:009andatotalrateofNqq(cid:1) (cid:3)0:057(cid:6)0:002(cid:4)exp:(cid:5)(cid:6)0:015(cid:4)BF(cid:5) (cid:1)(cid:1) per
p (cid:1)c c
hadronicevent,wheretheexperimentalerrorismuchsmallerthanthatduetothebranchingfractioninto
the reconstructed decay mode, pK(cid:2)(cid:3)(cid:1). In (cid:2)(cid:4)4S(cid:5) decays we measure a total rate of N(cid:2) (cid:3)0:091(cid:6)
(cid:1)c
0:006(cid:4)exp:(cid:5)(cid:6)0:024(cid:4)BF(cid:5)per(cid:2)(cid:4)4S(cid:5)decay,andfindamuchsoftermomentumdistributionthanexpected
from Bdecays into a (cid:1)(cid:1) plus an antinucleon and one to three pions.
c
DOI: 10.1103/PhysRevD.75.012003 PACS numbers: 13.66.Bc, 13.20.He, 13.60.Rj
I. INTRODUCTION heavyquark,with P(cid:4)x (cid:5)being much harder forbhadrons
p
thanchadrons,andinsomecasesonthemassandquantum
The production properties of charmed baryons in e(cid:1)e(cid:2)
numbers of H. Hadrons containing the same heavy quark
annihilations into cc(cid:1) and in decays of bottom (b) hadrons
type are generally predicted to have quite similar P(cid:4)x (cid:5),
probe different aspects of strong interaction physics. p
although differences between mesons and baryons have
Experiments running at and below the (cid:2)(cid:4)4S(cid:5) resonance
been suggested [13,14]. Measurements of P(cid:4)x (cid:5) serve to
areuniquelypositionedtoexploreeachoftheseprocesses p
constrain perturbative QCD and these model predictions.
in detail. The CLEO experiment has made precise studies
Furthermore, measurements for a given c or b hadron at
of charmed mesons in this way [1], and the larger data p
different (cid:1)s(cid:1)(cid:1)cantestQCDevolution,andcomparisonsofc-
samplesavailableattheBfactorieshaveallowedimproved
andb-hadrondistributionscantestheavy-quarksymmetry
studiesofcharmedmesons[2]andthefirstprecisestudies
[15].
of charmed baryons[2,3].
Heavy hadrons (H) produced in e(cid:1)e(cid:2) annihilations Theinclusiveb-hadronscaledenergydistributionandits
averagevalueof0.71havebeenmeasuredprecisely[16]by
provide a laboratory for the study of heavy-quark (cid:4)Q(cid:3)
experiments at the Z0, using partial reconstruction tech-
c;b(cid:5) jet fragmentation, in terms of both the relative pro-
niques. However, these techniques do not distinguish the
duction rates of hadrons with different quantum numbers
differenttypesofbhadrons.TherelativeproductionofB(cid:2),
andtheirassociatedspectra.Thelattercanbecharacterized u
B0, B0, excited b mesons, and b baryons have been mea-
in terms of a scaled energy or momentum, such as x (cid:7) d s
p
sured [4,17], but with limited precision and no sensitivity
p(cid:8)=p(cid:8) ,wherep(cid:8) isthehadronmomentuminthee(cid:1)e(cid:2)
H max H q(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:1) to differences in their xp distributions. Several c mesons
center-of-mass(c.m.)frameandp(cid:8)max (cid:3) s=4(cid:2)m2H isthe have been studied at the Z0 [18], but it is difficult to
maximummomentumavailabletoaparticleofmassm at disentangle the leading charm and b-decay contributions
p p H
a c.m. energy of (cid:1)s(cid:1)(cid:1). For (cid:1)s(cid:1)(cid:1)(cid:9)2m it has been observed andneithercomponentismeasuredprecisely.Recentmea-
H
[4] that the x distributions P(cid:4)x (cid:5) for heavy hadrons peak surements below BB(cid:1) threshold [1,2] have good precision
p p
at relatively high values, and that very few b hadrons are over the full x range and show substantial differences
p
produced apart from those containing initial b quarks, so between the pseudoscalar D and vector D(cid:8) meson states.
that one can probe leading b-hadron production directly. P(cid:4)x (cid:5) has been measured below BB(cid:1) threshold for two
p p
This is also the case for charmed (c) hadrons when (cid:1)s(cid:1)(cid:1)< charmed baryons, (cid:1)(cid:1) by CLEO [19] and Belle [2], and
c
2mB, where mB is the mass of the lightest b meson, but (cid:4)0c byBABAR[3],butwithlimited statistics,especially at
above BB(cid:1) threshold a large fraction of the c hadrons are low x . In this article we use the excellent particle identi-
p
b-hadron decay products. fication of the BABAR experiment to isolate (cid:1)(cid:1) baryons
c
Since the hadronization process is intrinsically nonper- (the inclusion of charge conjugate states is implied
turbative, P(cid:4)xp(cid:5) cannot be calculated using perturbative throughout) inpa large data sample collected below BB(cid:1)
quantum chromodynamics (QCD).However,ahighquark threshold, at (cid:1)s(cid:1)(cid:1)(cid:3)10:54 GeV. We measure P(cid:4)x (cid:5) pre-
p
mass provides a convenient cutoff point and the distribu- cisely, and compare our results with available predictions
tion of the scaled momentupm of the heavy quark before and previous measurements of heavy hadrons.
hadronization, xQ (cid:7)2p(cid:8)Q= (cid:1)s(cid:1)(cid:1), can be calculated [5–8]. The large b-hadron masses allow many hadronic decay
The observable P(cid:4)x (cid:5) is thought to be related by a simple modes, a small fraction of which have been studied in
p
convolution or hadronization model. Several phenomeno- detail. The (cid:2)(cid:4)4S(cid:5)resonance providesaunique laboratory,
logical models of heavy-quark fragmentation have been inwhichnobbaryonsareproducedanddecaysofmesons
proposed [9–12]. Predictions depend on the mass of the intobaryonscanbestudieddirectly.Manycbaryonshave
012003-4
INCLUSIVE(cid:1)(cid:1) PRODUCTIONINe(cid:1)e(cid:2) ... PHYSICALREVIEW D75, 012003 (2007)
c
been observed in inclusive (cid:2)(cid:4)4S(cid:5) decays [4] and the low light(DIRC).TheDCHgasishelium:isobutane80:20and
rate of associated leptons and high rate of ‘‘wrong-sign’’ a typical cell size is 18 mm. A truncated mean algorithm
(cid:1)(cid:1)[20]suggestinterestingdynamics.Howeveronlyafew gives a dE=dx value for each track with an average reso-
c
exclusive decays with cbaryonshave been observed [21– lution of 7.5%, from which we calculate a set of five
23]. Again, momentum distributions have been measured relative likelihoods LDCH for the particle hypotheses i(cid:3)
i
only for the (cid:1)(cid:1) [2,24] and (cid:4)0 [3] with limited precision. e,(cid:6),(cid:3),K,andp.Differencesbetweenthelog-likelihoods
c c p
Hereweusedatacollectedonthe(cid:2)(cid:4)4S(cid:5)resonance( (cid:1)s(cid:1)(cid:1)(cid:3) lDCH (cid:3)ln(cid:4)LDCH(cid:5)(cid:2)ln(cid:4)LDCH(cid:5) are used as input to the par-
ij i j
10:58 GeV) and subtract the e(cid:1)e(cid:2) !cc(cid:1) contribution ticle identification algorithm.
p
measured at (cid:1)s(cid:1)(cid:1)(cid:3)10:54 GeVtomakeaprecise measure- The DIRC comprises 144 fused silica bars that guide
mentofthe(cid:1)(cid:1)momentumdistributioninBmesondecays, Cherenkov photons to an expansion volume filled with
c
which we comparewith a number of possible models. water and equipped with 10752 photomultiplier tubes.
InSec.II,wedescribetheBABARdetector,inparticular, The fused silica refractive index is 1.473, corresponding
the particle identification capabilities essential to these to Cherenkov thresholds of 128, 458, and 867 MeV=c for
measurements.InSecs.IIIandIV,wediscusstheselection pions, kaons, and protons, respectively. A particle well
of (cid:1)(cid:1) candidates and the measurement of their x distri- above threshold yields 20–75 measured photons, each
c p
butions,respectively. We interpret the results for e(cid:1)e(cid:2) ! with a Cherenkov angle resolution of about 10 mrad. A
qq(cid:1) events and (cid:2)(cid:4)4S(cid:5) decays in Secs. V and VI, respec- globallikelihoodalgorithmconsidersallthereconstructed
tively,and summarize in Sec. VII. charged tracks and detected photons in each event and
assignseach track a set of likelihoods LDIRC.
i
The DCH provides excellent K-(cid:3) and p-K separation
II.APPARATUSANDEVENTSELECTION
for momenta in the laboratory frame below 0.5 and
In this analysis, we use data samples corresponding to 0:9 GeV=c, respectively. The DIRC provides very good
p
9:5 fb(cid:2)1 ofintegrated luminosity at (cid:1)s(cid:1)(cid:1)(cid:3)10:54 GeVand separationformomentaabove1.0and1:5 GeV=c,respec-
p
81 fb(cid:2)1 on the (cid:2)(cid:4)4S(cid:5) resonance, (cid:1)s(cid:1)(cid:1)(cid:3)10:58 GeV. The tively. In both detectors the separation power is lower for
BABAR detector is located at the PEP-II asymmetric- trackswithpolaranglesnear90(cid:12) inthelaboratorythanfor
energy e(cid:1)e(cid:2) collider at the Stanford Linear Accelerator moreforwardorbackwardtracks.Tominimizethesystem-
Center and is described in detail in Ref. [25]. We use atic errors in this analysis, the identification efficiencies
charged tracks measured in the five-layer, double sided mustnotvaryrapidlyasafunctionofmomentumorpolar
siliconvertextracker(SVT)andthe40-layerdriftchamber angle.Wehavethereforedevelopedanalgorithmthatuses
(DCH). In a 1.5 T axial magnetic field, they provide a linearcombinations oflDCH andlDIRC chosentominimize
ij ij
combined resolution on the momentum p transverse to suchvariations.ItisdescribedindetailinRef.[26]andits
T
the beam axis of (cid:10)(cid:5)(cid:4)p (cid:5)=p (cid:11)2 (cid:3)(cid:10)0:0013p (cid:11)2(cid:1)0:00452, performance for tracks used in this analysis is shown as a
T T T
where p is measured in GeV=c. function of momentum in Fig. 1. The identification effi-
T
Chargedparticleidentificationusesacombinationofthe ciencies are better than 99% at low momenta and above
energy loss (dE=dx) measured in the DCH, and informa- 90%forthemajorityof(cid:1)(cid:1) decayproducts.Theyareseen
c
tion from the detector of internally reflected Cherenkov to vary smoothly with momentum, and are almost inde-
1.0 0.10
y0.8 π → π 0.08
nc K → π M
Efficie0.6 p → π Kπ →→ KK pπ →→ pp 0.06isiden
on p → K K → p tific
cati 0.4 0.04atio
ntifi n R
e a
Id0.2 0.02te
0.0 0
0 1 2 3 4 0 1 2 3 4 0 1 2 3 4
Laboratory Momentum (GeV/c)
FIG. 1. Efficiencies for identifying (solid symbols, left-hand vertical scale) or misidentifying (open symbols, right-hand scale)
selectedpions(circles),kaons(squares),andprotons(triangles)withintheDIRCacceptanceaspions(left),kaons(center),orprotons
(right). They are extracted from control samples in the data as smooth functions of momentum and polar angle, and shown in
momentum bins averaged over the polar angle range used. The error bars indicate the average uncertainty due to control sample
statistics.
012003-5
B. AUBERTet al. PHYSICALREVIEW D75, 012003 (2007)
pendent of polar angle except near 0:8 GeV=c and calculate their combined four momentum from their
(1:2 GeV=c) for pions and kaons (protons), where they momenta at their points of closest approach to the beam
are as much as 10% lower for central tracks than for axis.Thedistributionsofinvariantmassforthecandidates
forward/backward tracks. The misidentification rates de- in the on- and off-resonance data are shownin Fig.2; (cid:1)(cid:1)
c
pend strongly on polar angle in the momentum regions signals of about 137000 and 13000 decays, respectively,
0.6–0.8,1.1–1.3,and2:5–3:5 GeV=c.Theyarebelow5% arevisible over nearly uniform backgrounds.
everywhere except that the rate for kaons (protons) to be The (cid:1)(cid:1) reconstruction efficiency depends primarily on
c
misidentified as pions reaches 11% at 0:7(cid:4)1:2(cid:5) GeV=c for themomentapandpolarangles(cid:8)ofthedaughtertracksin
themostcentraltracks.Theserateshavenegligibleeffects thelaboratoryframe.Toreducesystematicuncertainty,we
ontheresults.About16%oftheselectedtrackshavegood apply an efficiency correction to each candidate before
DCHinformationbutareoutsidetheDIRCfiducialaccep- boosting it into the e(cid:1)e(cid:2) c.m. frame. The efficiencies for
tance. These can be identified with essentially the same reconstructing and identifying tracks from pions, kaons,
efficiencies as in Fig. 1 for pion and kaon (proton) mo- and protons are determined from large control samples in
menta below0:6(cid:4)0:9(cid:5) GeV=c. the data as two-dimensional functions of (cid:4)p;(cid:8)(cid:5). We use
The event selection requires three or more charged theseefficienciesindedicatedsimulationsofqq(cid:1)and(cid:2)(cid:4)4S(cid:5)
tracks in the event, which retains any e(cid:1)e(cid:2) !qq(cid:1) event events containing a (cid:1)(cid:1) baryon that is decayed into
c
or (cid:2)(cid:4)4S(cid:5) decay containing a reconstructable (cid:1)(cid:1) ! pK(cid:2)(cid:3)(cid:1). From these we calculate the (cid:1)(cid:1) selection effi-
c c
pK(cid:2)(cid:3)(cid:1) decay andsuppressesbeam-related backgrounds. ciency"asasmoothtwo-dimensionalfunctionof(cid:4)p;(cid:8)(cid:5)of
We evaluate its performance using a number of simula- the (cid:1)(cid:1). We check that the efficiency does not depend on
c
tions, each consisting of a generator for a certain type of other track or event variables, in particular, that it is the
event combined with a detailed simulation of the BABAR sameinsimulatedqq(cid:1) and(cid:2)(cid:4)4S(cid:5)eventsforgivenvaluesof
detector [27]. For e(cid:1)e(cid:2) !qq(cid:1) events we use the JETSET (cid:4)p;(cid:8)(cid:5). The resolutions on the (cid:1)(cid:1) momentum and polar
c
[28] generator and for (cid:2)(cid:4)4S(cid:5) events we use our own anglearemuchsmallerthanthebinsizesusedbelow,sowe
generator, EVTGEN [29], in which the (cid:2)(cid:4)4S(cid:5) decays include resolution effects by defining the efficiencyas the
intoaBB(cid:1) pair,thentheBandB(cid:1) decayusingacombination number of (cid:1)(cid:1) reconstructed within a given (cid:4)p;(cid:8)(cid:5) range
c
of measured exclusive and semiexclusive modes, and a divided by the number generated in that range, using
b!cW(cid:2) model tuned to the world’s inclusive data. We ranges smaller than the relevant bin sizes. We test the
study large samples of simulated two-photon, (cid:7)-pair, and efficiency using a number of simulations, and find biases
radiativee-and(cid:6)-pairevents,andfindtheircontributions to be below 1%.
to both signal and background to be negligible. The efficiency varies rapidly near the edges of the
detector acceptance andat verylowmomenta inthe labo-
III.(cid:1)(cid:1) !pK(cid:2)(cid:3)(cid:1) SELECTION ratory.Wemakethetightfiducialrequirement that (cid:8)(cid:8),the
c polar angle of the (cid:1)(cid:1) candidate in the e(cid:1)e(cid:2) c.m. frame,
c
Weconstruct(cid:1)(cid:1)c candidatesfromchargedtracksthatare satisfy (cid:2)0:7<cos(cid:8)(cid:8)<0:2, which reduces model depen-
consistent with originating at the e(cid:1)e(cid:2) interaction point
dence and rejects all candidates in regions with efficiency
and have good tracking and particle identification infor-
mation. Each track must have: (i) at least 20 measured
3 3
coordinates in the DCH; (ii) at least 5 coordinates in the x10 x10
2
SVT,including at least three in the direction along the e(cid:2)
) O
2 15
bbeealomw;(1iiim)ma;diasntadnc(iev)ofaczlo-csoeostrdaipnpartoeaacthtthoisthpeobinetamwiathxiins eV/c ff-Re
10 cm of the nominal interaction point. These criteria (M so
ensure good quality information from the DCH and a s / na
e10 n
wtraepllo-mlateeadsutrraejdecetonrtryainncteerasencgtlseaiDntIoRtChebaDrIthReCn.thIfetthraeckexis- Entri 1ce E
accocmebpitnededifDitCisHidaenndtifiDeIdRaCsaalpgioorni,thkmao.nI,fornoptr,ottohnenbyitthies nce ntrie
a s
accepted ifitisidentifiedasaproton(pionorkaon)using on 5 / (
DCH information only and has a momentum below es Me
1:2(cid:4)0:6(cid:5) GeV=c. R V
n- /c
We considera combination ofthree charged tracks as a O 2
)
(cid:1)(cid:1)candidateifthetotalchargeis(cid:1)1,oneofthepositively 0 0
c 2.24 2.26 2.28 2.30 2.32
charged tracks is identified as a proton and the other as a pK−π+ Mass (GeV/c2)
pion, and the negatively charged track is identified as a
kaon. With the appropriate particle type assigned to each FIG. 2. Invariant mass distributions for (cid:1)(cid:1) candidates in the
c
track, we correct their measured momenta for energy loss on-(black) and off-resonance (gray) data.
012003-6
INCLUSIVE(cid:1)(cid:1) PRODUCTIONINe(cid:1)e(cid:2) ... PHYSICALREVIEW D75, 012003 (2007)
c
below about 5%, including those with a total laboratory
IV. SIGNALEXTRACTION
momentum below about 0:7 GeV=c. A feature of the
boosted c.m. system is that true (cid:1)(cid:1) baryons with low To estimate the number of (cid:1)(cid:1) !pK(cid:2)(cid:3)(cid:1) decays in
c c
c.m. momentum p(cid:8) are boosted forward and often have each x bin in the data, we fit the weighted invariant
p
all three tracks in the detector acceptance, giving efficient mass distribution with a function comprising signal and
access to the full p(cid:8) range. background components. Based on the simulated mass
WedefineA asthefractionofthe(cid:1)(cid:1)ineventsoftypek distributions, we describe the signal with a sum of two
k c
producedwithinourfiducialrange(cid:2)0:7<cos(cid:8)(cid:8)<0:2.In Gaussian functions of common meanvalue, one of which
(cid:2)(cid:4)4S(cid:5)!BB(cid:1) !(cid:1)(cid:1)Xdecays,thetruecos(cid:8)(cid:8)distributionis has 1.5 times the width and one quarter of the area of the
c
uniformandA (cid:3)0:45.Incc(cid:1) eventstheangulardistribu- other,andcorrectfora1.3%residualbiasinthefittedarea.
(cid:2)
tion of the initial c-quark follows 1(cid:1)cos2(cid:8)(cid:8), and we use We check the simulated bias by comparing with a single
theJETSETsimulationtocalculatethedistributionfor(cid:1)(cid:1) Gaussiansignalfunction.Thechangeintheyieldsis1.2%
c
after QCD radiation and hadronization. Soft (cid:1)(cid:1)c are pro- in both data and simulation.
duced predominantly in events with hard gluon radiation, The simulation predicts a nearly uniform background
which flattens the distribution considerably. The resulting overthepK(cid:2)(cid:3)(cid:1)massrangeshowninFig.2.Wesearchfor
valueofAcc(cid:1) is0.46atp(cid:8) (cid:3)0,andfallswithincreasingp(cid:8) reflectionsinthedatabychangingtheparticlemassassign-
toward an asymptotic value of 0.38. ments. We observe signalsforD(cid:1) !K(cid:2)(cid:3)(cid:1)(cid:3)(cid:1) ((cid:3)(cid:1) mis-
We bin candidates according to their reconstructed val- identifiedasp)andD(cid:1) !K(cid:2)K(cid:1)(cid:3)(cid:1)(K(cid:1)misidentifiedas
s
ues of xp (cid:3)p(cid:8)=p(cid:8)max, where p(cid:8)max is calculated for each p)atverylowlevelsconsistentwiththepredictionsofour
event from its c.m. energy and the nominal (cid:1)(cid:1) mass [4]. detector simulation, but no unexpected structure. From
c
Figure 3 shows the average value in each x bin of the these studies we calculate that reflections known to give
p
productA (cid:4)p(cid:8)(cid:5)(cid:13)"(cid:4)p;(cid:8)(cid:5)forselectedcandidatesintheoff- broad structures in the vicinity of the (cid:1)(cid:1) peak, such as
cc(cid:1) c
resonancedata.Itrangesfrom8%atlowx to19%athigh D(cid:8)(cid:1) !K(cid:2)(cid:3)(cid:1)(cid:3)(cid:1) ((cid:3)(cid:1) misidentified as p) contribute a
p
x . The error bars represent the statistical uncertainty on number of entries in each bin much smaller than the
p
the efficiency calculation. The corresponding quantity for statistical fluctuations. We also study processes such as
(cid:1)(cid:1)c from(cid:2)(cid:4)4S(cid:5)decays,hA(cid:2) (cid:13)"(cid:4)p;(cid:8)(cid:5)i,isslightlyhigherat (cid:9)(cid:1)c(cid:1) !(cid:1)(cid:1)c(cid:3)(cid:1), with the wrong (cid:3)(cid:1) included in the (cid:1)(cid:1)c
lowx duetoasmalldependenceof"on(cid:8),andrisesfaster candidate, and find their contributions to be negligible. In
p
with increasing xp since A(cid:2) is constant, whereas Acc(cid:1) each xp bin, a linear function describes the mass distribu-
decreases. We give each candidate a weight equal to the tioninthedataoverawiderangeawayfromthe(cid:1)(cid:1)c peak
inverse of either A (cid:13)" orA (cid:13)",asspecified below.The region,soweusealinearbackgroundfunctionandperform
cc(cid:1) (cid:2)
RMSdeviation of theweights in each bin is alwaysmuch fitsover the range 2235–2335 MeV=c2.
smaller than the averagevalue. Wefirstfitthefulldatasampleineachxpbininorderto
study mass resolution and bias. These fits yield (cid:1)(cid:1) mass
c
values that vary slightly with x in a manner consistent
p
withthesimulationandourrecentmeasurementofthe(cid:1)(cid:1)
c
0.20 mass [30]. The fitted mass resolutions (RMS width of the
y signalfunction)areshownasafunctionofx inFig.4.The
c p
en simulation is consistent with the data at low xp, and is
Effici0.15 slightlyoptimistic athighxp.The effect ofthisdifference
on the efficiency estimate is negligible.
×
e Nextwefixthemeanandwidthofthesignalfunctionin
c
n each x bin to values from linear parametrizations, and
a0.10 p
pt perform fits to the on- and off-resonance data separately.
e
c Dividingthesignalyieldsbytheintegratedluminosity,bin
c
A width, and branching fraction BpK(cid:2)(cid:3)(cid:1) (cid:7)B(cid:4)(cid:1)(cid:1)c !
0.05 pK(cid:2)(cid:3)(cid:1)(cid:5)(cid:3)5:0(cid:6)1:3% [4] gives the differential produc-
tion cross sections shown in Fig. 5 with statistical errors
only.Weusethee(cid:1)e(cid:2) !cc(cid:1) acceptancefactorA forthe
cc(cid:1)
0 off-resonancedataand,forpurposesofthiscomparison,an
0 0.2 0.4 0.6 0.8 1
average value of A in each bin weighted by the relative
x
p production rates measured below (see Tables I and V) for
FIG. 3. Average value of A (cid:13)", the (cid:1)(cid:1) !pK(cid:2)(cid:3)(cid:1) accep- theon-resonancedata.Therearetwobroadpeaksintheon-
cc(cid:1) c
tance times reconstruction efficiency, for candidates in the off- resonancecrosssection,correspondingtothecontributions
resonance data in bins of scaled momentum xp. The error bars from(cid:2)(cid:4)4S(cid:5)decaysatlowxp andfrome(cid:1)e(cid:2) !cc(cid:1) events
represent the average statistical uncertainty. athighx .Forx >0:47,thekinematiclimitforaBdecay
p p
012003-7
B. AUBERTet al. PHYSICALREVIEW D75, 012003 (2007)
production rates per event discussed in the following
6
sections.
Data
We consider several sources of systematic uncertainty.
)
2c Simulation We propagate the uncertainties on the measured track
V/
e finding and particle identification efficiencies by recalcu-
M
lating "(cid:4)p;(cid:8)(cid:5) with all efficiencies of a given type varied
(
n 5 simultaneously and repeating the fits. Tracking gives an
o
uti uncertainty of 2.5% and the particle identification contri-
ol butions total 1.5%–2.1%, depending on x . We obtain a
s p
e 0.9% uncertainty due to the resonant substructure of the
R
s (cid:1)(cid:1)c !pK(cid:2)(cid:3)(cid:1) decay similarly. The uncertainty on our
s
a integrated luminosity is 1.0%. Simulation statistics con-
M 4
tribute2%–4%wheretherateissignificantlynonzero.We
checkthefittingprocedurebyfloatingthesignalmeanand/
or width, fixing them to nominal or fitted values, using a
0 0.2 0.4 0.6 0.8 1 single Gaussian signal function, using a quadratic back-
x
p ground function, and varying the bin size. All changes in
thesignalyieldsarelessthanthecorrespondingstatistical
FIG. 4. RMSwidthofthefitted(cid:1)(cid:1) signalfunctioninthedata
c errors, and we take the largest change in each x bin as a
(circles) and simulation (squares) as a function of x . The line p
p systematic uncertainty. Each simulated bias is varied by
represents a linear parametrization of the data.
(cid:6)50%; together they contribute 0.7% to the systematic
uncertainty. The imperfect x distribution used in the
p
including a (cid:1)(cid:1)c and an antiproton, the two cross sections efficiencycalculation canaffecttheresultiftheefficiency
are consistent, indicating no visible contribution from varies over the width of an x bin. We recalculate the
p
(cid:2)(cid:4)4S(cid:5) events. efficiency with the input distribution shifted by plus and
Weextractthecrosssectionfor(cid:2)(cid:4)4S(cid:5)decaysbyrepeat- minus our bin width to derive a conservative limit on any
ingtheanalysisusingA(cid:2) forbothdatasets.Ineachxp bin sucheffectof0.5%–1.9%,dependingonxp,whichwetake
we then subtract the off-resonance cross section, scaled as a systematic uncertainty.
down by 0.8% to account for the dependence of the cross Wealsoperformseveralsystematicchecksoftheresults.
section on the c.m. energy, from the on-resonance cross The cross sections measured separately for (cid:1)(cid:1) and (cid:1)(cid:1)(cid:2),
c c
section. We divide the off-resonance and (cid:2)(cid:4)4S(cid:5) cross
which have very different efficiencies at low laboratory
sections by the e(cid:1)e(cid:2) !hadrons and effective e(cid:1)e(cid:2) !
momentum,areconsistent.Crosssectionsmeasuredinsix
(cid:2)(cid:4)4S(cid:5)crosssections,respectively,toyield the differential different regions of cos(cid:8)(cid:8) are consistent with each other.
Because of the boosted c.m. system, these would be af-
fected differently by any deficiency in the detector simu-
lation, especially at low x . They also have very different
nit) A values,andthesestudipesindicatethattheuncertainties
u cc(cid:1)
b / 500 duetoboththeproductionanglemodelincc(cid:1)eventsandthe
p value of the boost are negligible.
(
n 400 V.RESULTS FOR p(cid:1)s(cid:1)(cid:1)(cid:3)10:54 GeV
o
ecti300 A.(cid:1)(cid:1) Baryon production
S c
s The differential (cid:1)(cid:1) production rate per hadronic event
s c
Cro200 (cid:4)1=Nqq(cid:1)(cid:5)(cid:4)dN(cid:1)qqc(cid:1)=dxp(cid:5) is tabulated in Table I and compared
al withpreviouscharmedbaryonmeasurementsinFig.6.We
nti100 distinguishbetweensystematicuncertaintiesthataffectthe
e
r shape of the cross section and those that affect only its
e
Diff 0 normalization. The former include both uncertainties that
are uncorrelated between bins and the parts of the corre-
0 0.2 0.4 0.6 0.8 1
lateduncertaintieswhosevaluesdependonx .Theuncer-
x p
p
taintyfromthefittingprocedurehasnegligiblecorrelation
FIG. 5. Differentialcrosssectionsfor(cid:1)(cid:1)(cid:1)(cid:1)(cid:1)(cid:2) productionin betweenbins,andthosefromtheparticleidentificationand
c c
the off-(circles) and on-resonance (open squares) data as func- theshiftofthesimulateddistributionhaveonlyveryshort-
tions of x . The errors are statistical only. rangecorrelations, soweincludethemintheuncorrelated
p
012003-8
INCLUSIVE(cid:1)(cid:1) PRODUCTIONINe(cid:1)e(cid:2) ... PHYSICALREVIEW D75, 012003 (2007)
c
TABLE I. (cid:1)(cid:1) differential production rate per hadronic event
c p
per unit xp at (cid:1)s(cid:1)(cid:1)(cid:3)10:54 GeV. The last column includes BaBar
experimental errors that are correlated between xp values and 0.15 CLEO
affect the shape of the distribution. Normalization uncertainties
p
x Belle
are given only on the total. d
q/c
qΛ
Systematic N
xp Range N1qq(cid:1) ddNx(cid:1)qpqc(cid:1) Statistical Error Independent Correlated ) dq0.10
q
N
0.000–0.025 0.0007 0.0009 0.0004 0.0001 1/
0.025–0.050 0.0033 0.0016 0.0012 0.0002 (
0.05
0.050–0.075 0.0008 0.0030 0.0011 0.0001
0.075–0.100 (cid:2)0:0023 0.0040 0.0013 0.0001
0.100–0.125 0.0105 0.0053 0.0020 0.0007
0.125–0.150 0.0065 0.0053 0.0041 0.0002
0
0.150–0.175 0.0172 0.0057 0.0024 0.0004
0.175–0.200 (cid:2)0:0006 0.0056 0.0036 0.0000 0 0.2 0.4 0.6 0.8 1
x
0.200–0.225 0.0197 0.0057 0.0038 0.0004 p
0.225–0.250 0.0180 0.0059 0.0039 0.0003
FIG. 6. Differential (cid:1)(cid:1) production ratepere(cid:1)e(cid:2) !qq(cid:1) event
0.250–0.275 0.0323 0.0061 0.0064 0.0006 c
compared with previous measurements. The error bars include
0.275–0.300 0.0324 0.0056 0.0040 0.0006
statisticsandthosesystematic errorsthataffectthe shape.Each
0.300–0.325 0.0273 0.0054 0.0064 0.0006
experimenthasanormalizationuncertaintyofafewpercent,and
0.325–0.350 0.0517 0.0056 0.0053 0.0011 there is an overall 26% uncertainty due to the (cid:1)(cid:1) !pK(cid:2)(cid:3)(cid:1)
c
0.350–0.375 0.0509 0.0053 0.0029 0.0010
branching fraction.
0.375–0.400 0.0617 0.0054 0.0045 0.0012
0.400–0.425 0.0759 0.0055 0.0040 0.0014 cient in the latter exceeds unity.The suminquadrature of
0.425–0.450 0.0667 0.0051 0.0032 0.0010
the uncorrelated uncertainties is listed in the ‘‘indepen-
0.450–0.475 0.0939 0.0055 0.0044 0.0014
dent’’ column of Table I. It is typically 3% in the peak
0.475–0.500 0.1051 0.0056 0.0041 0.0014
region, increasing to 10% where the cross section is one-
0.500–0.525 0.1126 0.0056 0.0048 0.0014
thirdofitspeakvalue,andbecomingrelativelylargeatthe
0.525–0.550 0.1220 0.0056 0.0043 0.0015
ends of the x range. The square roots of the diagonal
0.550–0.575 0.1403 0.0058 0.0041 0.0014 p
elements of the remainder matrix are listed in the ‘‘corre-
0.575–0.600 0.1526 0.0058 0.0044 0.0015
lated’’ column of Table I, and included with the indepen-
0.600–0.625 0.1548 0.0058 0.0061 0.0014
dent and statistical components in the error bars in the
0.625–0.650 0.1394 0.0055 0.0038 0.0012
figures.
0.650–0.675 0.1409 0.0052 0.0045 0.0012
Allotheruncertaintiesarefullycorrelatedbetweenbins
0.675–0.700 0.1352 0.0052 0.0037 0.0011
0.700–0.725 0.1232 0.0049 0.0035 0.0010 and very nearly independent of xp, so are considered
0.725–0.750 0.0979 0.0043 0.0030 0.0009 experimental normalization uncertainties. They total
0.750–0.775 0.0803 0.0040 0.0026 0.0007 2.9%, dominated by the track-finding efficiency. There is
0.775–0.800 0.0673 0.0034 0.0035 0.0008 a26%uncertaintyonBpK(cid:2)(cid:3)(cid:1) thatalsoaffectsthenormal-
0.800–0.825 0.0464 0.0029 0.0026 0.0006 ization. The integral of the differential rate, taking the
0.825–0.850 0.0332 0.0025 0.0017 0.0004 correlation in the errors into account, gives the total rate,
0.850–0.875 0.0220 0.0020 0.0010 0.0005 listedatthebottomofTableIalongwiththenormalization
0.875–0.900 0.0161 0.0017 0.0017 0.0006 uncertainties. The product of the total rate per event and
00..990205––00..995205 00..00007499 00..00001132 00..00000076 00..00000038 branching fraction of N(cid:1)qqc(cid:1)(cid:13)BpK(cid:2)(cid:3)(cid:1)(cid:3)2:84(cid:6)0:04(cid:4)stat:(cid:5)(cid:6)
0:09(cid:4)syst:(cid:5)(cid:14)10(cid:2)3 is consistent with, and more precise
0.950–0.975 0.0018 0.0006 0.0003 0.0004
than, previous measurements. The normalization uncer-
0.975–1.000 0.0003 0.0001 0.0002 0.0001
taintiesarenotincludedinanyofthefigures,andallrates
Total 0.0568 0.0007 0.0006 0.0008 shownassume the samevalue of BpK(cid:2)(cid:3)(cid:1).
Norm. err. 0.0016 Assuming the (cid:1)(cid:1) are produced predominantly in
c
BFerror 0.0148 e(cid:1)e(cid:2) !cc(cid:1) events, the total rate corresponds to a rate of
Nc (cid:3)0:071(cid:6)0:003(cid:4)exp:(cid:5)(cid:6)0:018 (BF)(cid:1)(cid:1) per c-quark
(cid:1)c c
jet. Roughly10%oftheparticles inhigh-energyjets have
category. We express the error matrix for the efficiency generally been observed to be baryons [4], and our mea-
calculationasthesumofadiagonal‘‘uncorrelated’’matrix surement is consistent with 10% of c jets producing a c
and a remainder matrix, in which the elements of the baryon, with a large fraction of these decaying via a (cid:1)(cid:1).
c
former are as large as possible but no correlation coeffi- All known nonstrange charmed baryons decay predomi-
012003-9
B. AUBERTet al. PHYSICALREVIEW D75, 012003 (2007)
nantly through a (cid:1)(cid:1), whereas no (cid:10) states and only the ofthedistributionareoftheoreticalinterest.InTableIIwe
c c
heaviest observed (cid:4) states [31] are known to decay list values of the first six moments of the x distribution,
c p
through a (cid:1)(cid:1), so that 70%–85% of inclusive charmed calculatedbysummingoverbins.Theyareconsistentwith
c
baryons would be expected to decay through a (cid:1)(cid:1) in previous measurements from Belle [2]; all are 1–2 stan-
c
current hadronization models. darddeviationslower,butthemomentsarestronglycorre-
Theshapeofthedifferentialproductionrateisconsistent lated with each other. The hx i value of 0:574(cid:6)0:009 is
p
with previous results and measured more precisely. It is consistentwiththosemeasured[2]forD0andD(cid:1)mesons,
quite hard, as expected, peaking near xp (cid:3)0:6. We nor- and about 5% lower than those for D(cid:8)0 and D(cid:8)(cid:1) mesons.
malizetheratetounitareatoobtainP(cid:4)x (cid:5),andcompareit
p
withpreviouslymeasureddistributionsfor(cid:4)0c baryonsand B. Tests of c-quarkfragmentation models
DandD(cid:8) mesonsinFig.7.The(cid:4)0 distributionisnormal-
c Testing models of heavy-quark fragmentation can be
ized to have the same peak height as the (cid:1)(cid:1) distribution,
c problematic since the predictions are usually functions of
and, since it was measured on the (cid:2)(cid:4)4S(cid:5) resonance, is
a variable z that is not accessible experimentally, such as
shownonlyabovethekinematiclimitforB-mesondecays.
z (cid:3)(cid:4)E(cid:1)p (cid:5) =(cid:4)E(cid:1)p (cid:5) , z (cid:3)p =p , or z (cid:3)
The two charmed baryons have similar distributions, with 1 k H k Q 2 kH kQ 3
p =p (cid:4)p (cid:5),wherep representsamomentumprojec-
thatfortheheavierbaryonshiftedupinx byroughly0.05. H Hmax Q k
p
tion on the flight direction of the heavy quark before it
Although qualitatively similar, the D meson distributions
hadronizes. Monte Carlo event generators use similar in-
showbroaderpeaksthanthebaryondistributionsanddiffer
ternalvariables,andinsomecasescanbemadetoproduce
greatly in the way they fall toward zero at high x . The
p eventsaccordingtoagiveninputfunctionf(cid:4)z;(cid:11)(cid:5),where(cid:11)
charmed baryon and meson distributions are all much
representsthesetofmodelparameters.Inthiswayonecan
softer than the inclusive B-hadron distribution at c.m.
energies well above bb(cid:1) threshold, which peaks around test the large-scale features of any model, although the
detailed structure may not be reproduced exactly.
x (cid:3)0:75 [16].
p We consider the perturbative QCD calculations of
The average x value is often used in comparisons
p Collins and Spiller (CS) [5] and Braaten et al. (BCFY)
between differentheavyhadrons,andthehighermoments
[7], as well as the phenomenological models of
Kartvelishvili et al. for mesons (KLP-M) [9] and baryons
3 (KLP-B) [13], Bowler [10], Peterson et al. [11], the Lund
group[12],theUCLAgroup[14],andtheHERWIGgroup
(a)
Λ [32]. The latter two include heavy-quark fragmentation
c within their own generators, and the other seven predict
Ξ
2 c thefunctionalformslistedinTableIII.Weimplementeach
of these functions f(cid:4)z;(cid:11)(cid:5) within the JETSET generator.
)
p JETSETuses z as its internal variable, but z and z are
x 1 2 3
P( very similar at high x whereweare mostsensitive to the
1 p
n, shape. All distributions are affected by JETSET’s simula-
o tion of hard and soft gluon radiation.
cti WetesteachmodelagainstourmeasuredP(cid:4)x (cid:5)usinga
e p
S0 binned (cid:12)2
s 3
s
o
Cr Λc (b) (cid:12)2 (cid:3) Xn (cid:4)Pdata(cid:2)PMC(cid:5)V(cid:2)1(cid:4)Pdata(cid:2)PMC(cid:5); (1)
ed D0,D+ avg. i;j(cid:3)1 i i i;j j j
z
ali2 D*0,D*+ avg.
m
or TABLE II. Thefiprstsixmomentsofthe(cid:1)(cid:1)c xp distributionin
N hadronic eventsat (cid:1)s(cid:1)(cid:1)(cid:3)10:54 GeV.
1
Systematic
Moment Value Stat. Error Indep. Correl. Belle
hx i 0.5738 0.0061 0.0049 0.0032 0:5824(cid:6)0:0025
0 p
hx2i 0.3544 0.0038 0.0030 0.0021 0:3649(cid:6)0:0034
0 0.2 0.4 0.6 0.8 1 p
x hx3i 0.2305 0.0026 0.0021 0.0015 0:2396(cid:6)0:0023
p p
hx4i 0.1560 0.0020 0.0015 0.0011 0:1630(cid:6)0:0051
p
FIG. 7. xpdistributionfor(cid:1)(cid:1)c ine(cid:1)e(cid:2) !qq(cid:1)eventscompared hx5pi 0.1090 0.0015 0.0012 0.0009 0:1151(cid:6)0:0020
withthosemeasured for(a)(cid:4)0c byBABAR [3]and(b)charmed hx6i 0.0783 0.0012 0.0010 0.0008 0:0851(cid:6)0:0023
p
mesons by Belle [2].
012003-10