The Hunt for New Physics at the Large Hadron Collider

8.2 MB·English

by  P. Nath

0 The Hunt for New Physics at the Large Hadron Collider
1
0 Principal Conveners: Pran Natha
2 Brent Nelsona

n
a Conveners for New Physics Sections: Hooman Davoudiaslb (Extra Dimensions)
J
Bhaskar Duttac (Dark Matter)
4
Daniel Feldmand and Zuowei Liue (Hidden Sectors)
1
Tao Hanf (Top)

] Paul Langackerg (Z Prime)
h Rabi Mohapatrah and Jose Vallei (Neutrinos)
p
Pran Natha (SUSY)
-
p Brent Nelsona (Strings)
e Apostolos Pilaftsisj (CP violation)
h
Dirk Zerwask (Higgs)
[

1 ShehuAbdusSalaml,bb, Claire Adam-Bourdariosk, J.A. Aguilar-Saavedram, Benjamin Allanachl,
v B. Altunkaynaka, Luis A. Anchordoquin, Howard Baero, Borut Bajcp, O. Buchmuellerq, M. Carenar,s,
3
R.Cavanaught,u, S.Changv, Kiwoon Choiw, C. Cs´akix, S. Dawsonb, F. de Camposy, A. DeRoeckq,z,
9
M. Du¨hrssenaa, O.J.P. E´boliab, J.R. Ellisq, H. Fla¨cherq, H.Goldberga, W. Grimusac, U. Haischad,
6
2 S.Heinemeyerae, M. Hirschi, M. Holmesa, Tarek Ibrahimaf, G. Isidoriag, Gordon Kaned, K.Kongah,Remi
. Lafayeai, G. Landsbergaj, L. Lavouraak,Jae Sik Leeal, SeungJ. Leeam, M. Lisantiah, Dieter Lu¨stan,ao,
1 M.B. Magroap, R.Mahbubanit, M. Malinskyaq, Fabio Maltoniar, S. Morisii, M.M. Mu¨hlleitneras,
0
B. Mukhopadhyayaat, M. Neubertad, K.A.Oliveau, Gilad Perezam, Pavel Fileviez P´erezf, T. Plehnav,
0
E. Pont´onaw, WernerPorodax, F. Quevedol, M. Rauchas, D. Restrepoay, T.G. Rizzoah,J. C. Rom˜aoak,
1
F.J. Rongaaz, J. Santiagom, J. Schechterbb, G. Senjanovi´cbc, J. Shaobb, M. Spirabd, S.Stiebergeran, Zack
:
v Sullivanbe, Tim M.P. Taitbf, Xerxes Tataf,bg, T.R. Taylora, M. Tohariah, J. Wackerah, C.E.M. Wagners,bh,bi,
Xi Lian-Tao Wangbj, G. Weigleinbk, D. Zeppenfeldas,K. Zurekd
r
a
(a) Department of Physics, Northeastern Uni- (h) Maryland Center for Fundamental Physics
versity, Boston, MA 02115,USA and Department of Physics, University of Mary-
(b) Department of Physics, Brookhaven Na- land, College Park,MD, 20742
tional Laboratory,Upton, NY 11973, USA (i) AHEP Group, Instituto de F´ısica Corpus-
(c) Department of Physics, Texas A&M Uni- cular – C.S.I.C./Universitat de Val`encia, Cam-
versity, College Station, TX 77843-4242,USA pus de Paterna,Aptdo 22085,E–46071Val`encia,
(d) Michigan Center for Theoretical Physics, Spain
RandallLab.,UniversityofMichigan,AnnArbor, (j) School of Physics and Astronomy, Univer-
MI 48109 sityofManchester,ManchesterM139PL,United
(e)C.N.YangInstituteforTheoreticalPhysics, Kingdom
StonyBrookUniversity,Stony Brook,NY 11794, (k) LAL, Universit´e Paris-Sud, IN2P3/CNRS,
USA Orsay, France
(f) Department of Physics, University of Wis- (l) Department of Applied Mathematics and
consin, Madison, WI 53706,USA Theoretical Physics, Wilberforce Road, Cam-
(g) Institute for Advanced Study ,Princeton, bridge, CB3 0WA, United Kingdom
NJ 08540 (m)DepartamentodeF´ısicaTeo´ricaydelCos-
1
2
mos and CAFPE, Universidad de Granada, E- IN2P3/CNRS, Annecy, France
18071 Granada, Spain (aj) Department of Physics, BrownUniversity,
(n) Department of Physics, University of 182 Hope St, Providence, RI 02912,USA
Wisconsin-Milwaukee, Milwaukee, WI 53201, (ak) Technical University of Lisbon, Centre
USA forTheoreticalParticlePhysics,1049-001Lisbon,
(o) Dept. of Physics and Astronomy, Univer- Portugal
sity of Oklahoma, Norman, OK, 73019,USA (al)PhysicsDivision,NationalCenterforThe-
(p)J.StefanInstitute,1000Ljubljana,Slovenia oretical Sciences, Hsinchu, Taiwan
(q) CERN, CH-1211 Gen`eve 23, Switzerland (am) Department of Particle Physics, Weiz-
(r) Theoretical Physics Department, Fermilab, mann Institute of Science, Rehovot 76100,Israel
Batavia, IL 60510,USA (an)Max–Planck–Institutfu¨rPhysik,Werner–
(s)EFIandPhysicsDepartment,Universityof Heisenberg–Institut, 80805 Mu¨nchen, Germany
Chicago 5640 S. Ellis Ave., Chicago, IL 60637, (ao) Arnold Sommerfeld Center for Theo-
USA retical Physics, Ludwig-Maximilians-Universit¨at
(t) Fermi National Accelerator Laboratory, Mu¨nchen, 80333 Mu¨nchen, Germany
P.O. Box 500, Batavia, Illinois 60510, USA (ap) Centro Universit´ario Funda¸ca˜o Santo
(u) Physics Department, University of Illinois Andr´e, Santo Andr´e – SP, Brazil
at Chicago, Chicago, Illinois 60607-7059,USA (aq) Theoretical Particle Physics Group, De-
(v) Physics Department, University of Califor- partment of Theoretical Physics, Royal Institute
nia Davis, Davis, CA 95616 ofTechnology(KTH),Roslagstullsbacken21,SE-
(w) Physics Department, KAIST, Daejeon, 106 91 Stockholm, Sweden
305-701,Korea (ar) Center for Particle Physics and Phe-
(x) Institute for High Energy Phenomenology, nomenology, Universit´e Catholique de Louvain
Laboratory of Elementary Particle Physics, Cor- Chemin du Cyclotron 2, B-1348, Louvain-la-
nell University, Ithaca, NY 14853, USA Neuve, Belgium
(y) Departamento de F´ısica e Qu´ımica, Uni- (as) Institut fu¨r Theoretische Physik, Univer-
versidadeEstadualPaulista,Guaratingueta´–SP, sit¨at Karlsruhe, KIT, D–76128 Karlsruhe, Ger-
Brazil many
(z) Antwerp University, B-2610 Wilrijk, Bel- (at)RegionalCentreforAccelerator-basedPar-
gium ticlePhysics,Harish-ChandraResearchInstitute,
(aa) Physikalisches Institut, Universit¨at ChhatnagRoad,Jhunsi,Allahabad-211019,In-
Freiburg, Germany dia
(ab) Instituto de F´ısica, Universidade de Sa˜o (au)SchoolofPhysicsandAstronomy,Univer-
Paulo, Sa˜o Paulo – SP, Brazil sityofMinnesota,Minneapolis,Minnesota55455,
(ac) University of Vienna, Faculty of Physics, USA
Boltzmanngasse 5, A–1090 Vienna, Austria (av) Institut fu¨r Theoretische Physik, Univer-
(ad) Institut fu¨r Physik (THEP), Johannes sit¨at Heidelberg, Germany
Gutenberg-Universit¨at, D-55099 Mainz, Ger- (aw)DepartmentofPhysics,ColumbiaUniver-
many sity, New York, NY 10027,USA
(ae) Instituto de F´ısica de Cantabria (CSIC- (ax) Institut fu¨r Theoretische Physik und
UC), E–39005Santander, Spain Astronomie, Universit¨at Wu¨rzburg, D-97074
(af)DepartmentofPhysics,FacultyofScience, Wu¨rzburg, Germany
University of Alexandria, Alexandria, Egypt (ay) Instituto de F´ısica, Universidadde Antio-
(ag) INFN, Laboratori Nazionali di Frascati, quia, A.A 1226, Medellin, Colombia
Via E. Fermi 40, I–00044Frascati, Italy (az)InstituteforParticlePhysics,ETHZu¨rich,
(ah) SLAC National Accelerator Laboratory CH-8093 Zu¨rich, Switzerland
2575SandHillRd.,MenloPark,CA,94025,USA (ba) CAFPE and Departamento de F´ısica
(ai) LAPP, Universit´e de Savoie, Teo´rica y del Cosmos, Universidad de Granada,
3
E-18071Granada, Spain
(bb) Department of Physics, Syracuse Univer-
sity, Syracuse, NY 13244-1130,USA
(bc) International Centre for Theoretical
Physics, 34100 Trieste, Italy
(bd) Paul Scherrer Institut, CH–5232 Villigen
PSI, Switzerland
(be) Department of Biological, Chemical, and
PhysicalSciences,IllinoisInstituteofTechnology,
3101 S. Dearborn St., Chicago, IL 60616-3793,
USA
(bf) Department of Physics and Astronomy,
University of California, Irvine, CA 92697,USA
(bg) Dept. of Physics and Astronomy, Univer-
sity of Hawaii, Honolulu, HI , USA
(bh) KICP,University of Chicago 5640S. Ellis
Ave., Chicago, IL 60637,USA
(bi) HEP Division, Argonne National Labora-
tory 9700 S. Cass Ave., Argonne, IL 60439, USA
(bj) Department of Physics,PrincetonUniver-
sity, Princeton, NJ. 08544, USA
(bk) IPPP, University of Durham, Durham
DH1 3LE, United Kingdom
The Hunt for New Physics at the
Large Hadron Collider
Abstract
TheLargeHadronColliderpresentsanunprecedentedopportunitytoprobetherealmofnewphysicsin
theTeVregionandshedlightonsomeofthecoreunresolvedissuesofparticlephysics. Theseincludethe
natureofelectroweaksymmetrybreaking,theoriginofmass,thepossibleconstituentofcolddarkmatter,
new sourcesofCPviolationneededtoexplainthe baryonexcessinthe universe,thepossibleexistenceof
extra gauge groups and extra matter, and importantly the path Nature chooses to resolve the hierarchy
problem - is it supersymmetry or extra dimensions. Many models of new physics beyond the standard
model contain a hidden sector which can be probed at the LHC. Additionally, the LHC will be a top
factoryandaccuratemeasurementsofthepropertiesofthe topandits raredecayswillprovideawindow
to new physics. Further, the LHC could shed light on the origin of neutralino masses if the new physics
associated with their generation lies in the TeV region. Finally, the LHC is also a laboratory to test the
hypothesisofTeVscalestringsandDbranemodels. Anoverviewofthesepossibilitiesispresentedinthe
spirit that it will serve as a companionto the Technical Design Reports (TDRs) by the particle detector
groups ATLAS and CMS to facilitate the test of the new theoretical ideas at the LHC. Which of these
ideasstandsthetestoftheLHCdatawillgovernthecourseofparticlephysicsinthesubsequentdecades.
4
Contents
1 Introduction 10
1.1 Hunt for supersymmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
1.2 Hunt for the Higgs boson . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.3 CP violation at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.4 LHC and dark matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
1.5 Top physics at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.6 Z physics at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
′
1.7 Visible signatures from the hidden sector at the LHC . . . . . . . . . . . . . . . . . . . . . 12
1.8 Probing the origin of neutrino mass at the LHC . . . . . . . . . . . . . . . . . . . . . . . . 12
1.9 Hunt for extra dimensions at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
1.10 Hunt for strings at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
2 Hunt for Supersymmetry at the LHC 14
2.1 Hunt for SUSY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.1.1 Hyperbolic Branch / Focus Point (HB/FP) . . . . . . . . . . . . . . . . . . . . . . 16
2.2 A Brief Catalogue of SUSY Signatures at the LHC . . . . . . . . . . . . . . . . . . . . . . 19
2.2.1 Catalogue of SUSY signatures. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
2.2.2 Events with missing E . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20
T
2.2.3 Jet-free multilepton+Emiss events . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
T
2.2.4 Signals with isolated photons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
2.2.5 Signals from long-lived charged sparticles . . . . . . . . . . . . . . . . . . . . . . . 22
2.2.6 Events with displaced vertices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.7 Events containing intermittent tracks . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.8 Inclusive multilepton events without Emiss . . . . . . . . . . . . . . . . . . . . . . . 23
T
2.2.9 Resonance sparticle production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.10 Rapity gap events from SUSY. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
2.2.11 Final Remarks . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.3 LHC Measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.3.1 mSUGRA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
2.3.2 MSSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.3.3 Extrapolationto High Scale . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.4 Fits to the Phenomenological MSSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25
2.5 Mass and Spin Measurement with the Transverse Mass Variable M . . . . . . . . . . . . 29
T2
2.5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
2.5.2 M Kink . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
T2
2.5.3 MAOS Momentum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
5
6
3 Higgs Physics 36
3.1 Predictions for SUSY Higgses at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.1.1 Frequentist Fit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 36
3.1.2 Results for M . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37
h
3.1.3 Results for the Heavy Higgs Bosons . . . . . . . . . . . . . . . . . . . . . . . . . . 37
3.2 Higgs Boson Production at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2.1 Standard Model . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38
3.2.2 Minimal Supersymmetric Extension . . . . . . . . . . . . . . . . . . . . . . . . . . 40
3.3 Higgs decays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.3.1 Standard Model Higgs decays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
3.3.2 MSSM Higgs boson decays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
3.3.3 Higher order corrections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.3.4 Branching ratios and total widths . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
3.4 Higgs Signatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.4.1 Standard channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46
3.4.2 Mass measurements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
3.4.3 Error estimates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
3.4.4 Subjet analyses for H b¯b . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 50
→
3.4.5 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5 Alternative Higgs Scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5.1 Nonstandard Higgs Models and Decays . . . . . . . . . . . . . . . . . . . . . . . . 52
3.5.2 Discovering the Higgs with Low Mass Muon Pairs . . . . . . . . . . . . . . . . . . 53
3.6 Determination of Higgs-BosonCouplings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.6.1 Determination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
3.6.2 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58
3.7 On the Possible Observation of Light Higgses A,H,H at the LHC . . . . . . . . . . . . 59
±
3.7.1 Light Higgses in the SUGRA and String Landscape . . . . . . . . . . . . . . . . . 59
4 CP Violation at the LHC 67
4.1 CP violation in Supersymmmetric Theories . . . . . . . . . . . . . . . . . . . . . . . . . . 67
4.2 CP violation in the Higgs sector. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
4.3 CPX scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72
4.4 Trimixing scenario . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
4.5 Testing the Cancellation Mechanism at the LHC . . . . . . . . . . . . . . . . . . . . . . . 74
4.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75
5 Connecting Dark Matter to the LHC 79
5.1 Dark Matter at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79
5.1.2 mSUGRA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
5.1.3 mSUGRA at the LHC and the Determination of Dark Matter Content . . . . . . . 81
5.1.4 Stau-Neutralinno Coannihilation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82
5.1.5 Hyperbolic branch/Focus point . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
5.1.6 Bulk Region. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88
5.1.7 Over-Dense Dark Matter Region in the mSUGRA model. . . . . . . . . . . . . . . 89
5.1.8 Other Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89
5.1.9 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.2 Decoding the Origin of Dark Matter with LHC Data . . . . . . . . . . . . . . . . . . . . . 92
7
5.2.1 Decoding Dark Matter with the LHC . . . . . . . . . . . . . . . . . . . . . . . . . 92
5.2.2 Light Gluinos in SUGRA GUTS and discovery at the LHC . . . . . . . . . . . . . 94
5.2.3 CDMS II and LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
5.3 Lifting LHC Degeneracies Using Dark Matter Observations . . . . . . . . . . . . . . . . . 97
5.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.3.2 Degenerate Pairs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97
5.3.3 Direct Detection Experiments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
5.3.4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
6 Top-Quark Physics at the LHC 105
6.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.2 Standard Model Top-Quark Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.2.1 Top Quark Decay. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
6.2.2 tt¯Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
6.2.3 Single-top Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 107
6.3 New Physics in Top-Quark Decay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
6.3.1 Rare Decays into Standard Model Particles . . . . . . . . . . . . . . . . . . . . . . 109
6.3.2 Exotic Decays into Nonstandard Particles . . . . . . . . . . . . . . . . . . . . . . . 111
6.4 Top Quarks in New Resonant Production . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.4.1 Emergence of Top Jets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
6.4.2 Chiral Coupling to New Particles . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.5 Top-Rich Events for New Physics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
6.5.1 Signal of New Top Partners . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
6.5.2 Multiple Top Production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
6.6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7 Z Physics at the LHC 124
′
7.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
7.2 Formalism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
7.3 Existing Limits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125
7.4 The LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
7.4.1 Discovery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
7.4.2 Diagnostics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128
7.5 Other LHC Implications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131
8 Visible Signatures from Hidden Sectors 136
8.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 136
8.2 Stueckelberg Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
8.2.1 Massive Stueckelberg vector bosons . . . . . . . . . . . . . . . . . . . . . . . . . . 137
8.2.2 Explaining PAMELA PositronData . . . . . . . . . . . . . . . . . . . . . . . . . . 138
8.2.3 Stueckelberg Extension of MSSM . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
8.2.4 Enhancement of Relic Density via Coannihilation with Hidden Matter . . . . . . . 139
8.2.5 Narrow Resonances at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 139
8.2.6 Summary: Stueckelberg Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . 140
8.3 Hidden Valleys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
8.3.1 Overview and basic framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 141
8.4 Models of hidden dark matter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 142
8.4.1 Low mass dark sectors mediated by kinetic mixing . . . . . . . . . . . . . . . . . . 142
8
8.4.2 Low mass dark sectors as solutions to the baryon-dark matter coincidence . . . . . 143
8.4.3 Dark sectors with confinement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
8.4.4 Collider signatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
8.4.5 Summary of Low Mass Dark Sectors . . . . . . . . . . . . . . . . . . . . . . . . . . 145
8.5 Probing the GeV dark sector at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
8.5.1 Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
8.5.2 Basic framework . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 146
8.5.3 Production at the LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
8.5.4 Summary of GeV Dark Sector Signatures . . . . . . . . . . . . . . . . . . . . . . . 149
8.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149
9 Probing the Origin of Neutrino Mass at the LHC 153
9.1 Introduction. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
9.2 Seesaw Mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 153
9.2.1 Type-I seesaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
9.2.2 Type-II seesaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
9.2.3 Type-III seesaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 154
9.2.4 Double seesaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
9.2.5 Inverse seesaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
9.2.6 Linear seesaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
9.2.7 Inverse type-III seesaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 155
9.2.8 Nesting of seesaw mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
9.2.9 Loop models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
9.3 Phenomenology at LHC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 156
9.3.1 Type I seesaw . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
9.3.2 Type II Seesaw at the LHC. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 160
9.3.3 Charged fermions in type-III seesaw . . . . . . . . . . . . . . . . . . . . . . . . . . 164
9.3.4 Low-scale seesaw schemes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
9.4 R-parity violation: Theory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
9.4.1 R-parity violating supersymmetry . . . . . . . . . . . . . . . . . . . . . . . . . . . 166
9.4.2 Explicit bilinear R-parity violation . . . . . . . . . . . . . . . . . . . . . . . . . . . 167
9.4.3 Spontaneous RPV . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 168
9.4.4 The µνSSM . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169
9.5 R-parity: LHC studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
9.5.1 LSP decays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
9.5.2 Three and multi-lepton channels . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
9.5.3 Displaced LSP decays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
9.5.4 Displaced b-jets from Higgs decay . . . . . . . . . . . . . . . . . . . . . . . . . . . 172
9.5.5 Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 173
9.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 174
10 Extra Dimensions 179
10.1 A Short Overview of Large Extra Dimensions . . . . . . . . . . . . . . . . . . . . . . . . . 179
10.2 Mini-Black Holes at Modern Colliders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
10.2.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
10.2.2 Mini-black hole production and decay . . . . . . . . . . . . . . . . . . . . . . . . . 181
10.2.3 Monte Carlo generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
10.2.4 Experimental studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
9
10.3 On the Possible Observation of KK Excitations of SM states at the LHC. . . . . . . . . . 182
10.3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
10.3.2 Precision constraints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
10.3.3 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
10.4 Probing Universal Extra Dimensions at Colliders . . . . . . . . . . . . . . . . . . . . . . . 184
10.4.1 One and Two Universal Extra Dimensions . . . . . . . . . . . . . . . . . . . . . . . 184
10.4.2 Collider signals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 185
10.5 Signals of a Warped New Dimension at Colliders . . . . . . . . . . . . . . . . . . . . . . . 186
10.6 Precision Measurement Constraints on Warped Extra Dimensions . . . . . . . . . . . . . 188
10.7 Flavor physics in models with warped extra dimensions . . . . . . . . . . . . . . . . . . . 191
10.8 Radion Phenomenology in Warped Extra Dimensions. . . . . . . . . . . . . . . . . . . . . 193
10.9 A Brief Review of Higgsless Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 195
11 String Phenomenology and the LHC 202
11.1 New States and New Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202
11.1.1 Anomalous Vector Boson Couplings . . . . . . . . . . . . . . . . . . . . . . . . . . 202
11.1.2 Fractionally-ChargedExotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203
11.1.3 E -based Exotics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
6
11.2 Heterotic Orbifold Compactifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
11.2.1 Spectra in Semi-Realistic Orbifold Models . . . . . . . . . . . . . . . . . . . . . . . 206
11.2.2 Electroweak Symmetry Breaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
11.2.3 Supersymmetry Breaking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
11.3 D-Branes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
11.4 Compressed Spectra in Intersecting D-Brane Models . . . . . . . . . . . . . . . . . . . . . 210
11.5 M-Theory on Manifolds of G Holonomy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
2
11.5.1 Model description and soft terms . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
11.5.2 LHC Phenomenology. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
11.6 F-Theory Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
11.6.1 Review of F-theory GUTs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
11.6.2 LHC phenomenolgy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 215
11.7 Models of Supersymmetry Breaking Mediation, the LHC and Global Fits . . . . . . . . . 216
11.7.1 Large Volume String Scenario and LHC Signatures . . . . . . . . . . . . . . . . . . 216
11.7.2 Comparison of LVS and Other Models of SUSY Breaking . . . . . . . . . . . . . . 219
11.8 TeV-Scale String Excitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
12 Conclusion 233
Chapter 1
Introduction
ways in which one may connect the observed
Pran Nath
deviations from the Standard Model prediction
to the underlying new physics.
The Large Hadron Collider (LHC) when fully Thus the underlying theme of this report is to
operational will have an optimal center of mass provide an overview for experimentalists of the
energy in proton -proton collisions of √s = 14 testablenewphysicsattheLHC.Themaintopics
TeV and a design luminosity of 1034cm−2s−1. covered in the report are the following.
The main experiments at the LHC are: ALICE,
ATLAS, CMS, LHCb, and TOTEM. Of these 1. Hunt for supersymmetry
ALICE is devote to the study of heavy ion
2. Hunt for the Higgs boson
collisions, LHCb to the study of B physics, and
TOTEM to the study of total cross section, 3. CP violation at the LHC
elastic scattering and diffraction dissociation
at the LHC. Thus ATLAS1 and CMS2 are the 4. LHC and dark matter
primary detectors dedicated to the discovery
5. Top quark physics at the LHC
of new physics. It is expected that initially
LHC will run at √s = 7 TeV to collect data 6. Z physics at the LHC
′
for calibration, later ramping the CM energy to
√s=10 TeV, and then to √s=14 TeV. 7. Visiblesignaturesfromthehiddensectorat
the LHC
The particle physics capabilities of the AT-
8. Probing the origin of neutrino mass at the
LAS and CMS detectors are described in their
LHC
technical design reports (TDRs) [1,2] which
give an overview of their performance as the
9. Hunt for extra dimensions at the LHC
LHC begins its operation. The purpose of the
present document is to present a broad overview 10. Hunt for strings at the LHC
of the new physics possibilities that the LHC
We discuss below each of these topics briefly.
is likely to see. Of course, irrespective of the
particular nature of new physics the end product
1.1. Hunt for supersymmetry
at the LHC would be an excess of observed
leptons, photons, jets and missing energy in
Supersymmetry provides a technically natural
some combination. It is then necessary to devise
solutionto the socalledgaugehierarchyproblem
1ATorroidalLHCApparatuS. that arises in the non-supersymmetric unified
2CompactMuonSolenoid. theories with various mass scales. Gauging
10