[email protected]

0.83 MB·

by  Maria Spiropulu

[email protected]
Search, Navigation and Orientation
Maria Spiropulu1 a
Physics Department, CERN, CH 1211 Geneva 23
February 4, 2008
Abstract. I discuss the program of work towards discoveries at the LHC, and I include seeds for
8 orientation and navigation in the parameter space given the foreseen multitude of excesses at
0
startup.
0
2
PACS. 11.30.Pb,14.80.Ly,12.60.Jv

n
a
J 1 Introduction itscontentsemergethewayweobservethemintheex-

1 periments.

TheLargeHadronColliderwillproduce14TeVproton- Supersymmetry([1],[2],[3],[4])wasinitiallyconstructed
]
x proton collisions in probably less than a year from tohelpintroducefermionsinstringtheory([5]);string
e when this proceeding is published. ATLAS and CMS, theory itself was built to describe the quark interac-
p- arefocusingthisyearonthefinalcommissioningofthe tions (e.g. gluonic flux tubes; the jet “strings” in the
e experiments and what I call “engineering the discov- printout of a PYTHIA event is not a coincidence see
h eryplan”.Thestrategiesforthecarefulunderstanding e.g. [6],[7],[8],[9],[10]). Forty years of experimental re-
[ anduseoftheStandardModeldataat14TeVconsti- sults from accelerators, astrophysical and cosmologi-

1 tutes a large part of the readiness for discovery at the cal observations and progress in theory are pointing
v LHC. to LHC’s likelihood of discovering new physics.
Two are the major experimental observations that
8 While a number of modern theoretical frameworks
1 have emerged in the past decade, most all dual to the in concert with the theoretical considerations can be
3 previous canonical beyond-the-standard physics ideas usedascorroborativeevidenceforphysicsmechanisms
0 that broaden the Standard Model:
and models, supersymmetry appears to still have no
.
1 rivals as the top and favorite theory that embraces 1. the observed dark matter in the universe
0 and enhances the Standard Model at the TeV scale. 2. theobservedmassesoftheW andZ vectorbosons
8 In fact a lot, if not most, of the models implied above
0 TheexpectationisthenthattheLHCwilldiscover
end up looking eventually like SUSY at the TeV scale
: a new sector of particles/fields associated with elec-
v (UEDs, little-Higgs with T-parity etc). The rest post-
troweak symmetry breaking and dark matter. Super-
i pone the introduction of TeV new physics to multi-
X symmetry outputs both and is the best template of
TeV new physics.
discovery physics. Note that indeed we don’t know a-
r
I will not indulge in the theoretical reasons of why
a priori what the discoveries will be. Preparing for the
when we try to extend the Standard Model at short
discoveriesaheadoftimegiventhebesttemplatesdoes
distances, as short as the Planck length, we need the
not guarantee nor does it imply that these exact tem-
introduction of new theories. I would instead like to
plate(s) is what we (expect) will be found, nor that
remind ourselves that with the Standard Model we
the preparation strategies are sufficient and exact to
close a more than two thousand years cycle of theo-
assist the discoveries, come data time. It only implies
retical and experimental exploration into the nature
that we investigate in detail all we (think we) know,
of matter and its interactions. The Standard Model is
and think well on all we know we don’t know.
extremely successful and precise, to one part in a bil-
lion in many cases. Together with the general theory
ofrelativityitisfairtosaythatwehaveacorrectthe- 2 The program of work
ory of the known fundamental constituents of matter
and their interactions down to length scales of 10−18 2.1 Status of the experiments
cm. This by no means implies that we understand the
physicsmechanismsbywhichtheStandardModeland Both the ATLAS (A large ToroidaL ApparatuS) and
CMS (Compact Muon Solenoid) are in stage of com-
a Email: [email protected] missioning. Already both experiments are collecting
Maria Plenary
astrophysics data and finalizing the analysis of beam – try to match emerging pattern to tentative tem-
tests data of most-all detector elements.The details of plate models
their everyday progress, as well as the status of the – havingadjustedtemplatemodelstomeasurements,
accelerator can be found at the corresponding CERN trytofindadditionalsignaturestodiscriminatedif-
sites. The expected performance of the experiments ferent options
will be published in early 2008. According to the pub-
This program of work calls for “realistic” analyses
lished schedule of the lab (also see the LHC plenary
that prepares the experiments as thoroughly as pos-
talk in this meeting by Lyn Evans [11]) we expect 14
sible for the real data analyses. It implies identifying
TeV collisions before the end of 2008. While in what
and implementing the crucial groundwork in terms of
follows I focus on the searches for supersymmetry at
detector understanding, physics object requirements,
ATLAS and CMS I must point out that the discov-
trigger understanding and requirements, dataset def-
eryofsupersymmetryonlyemphasizesthemanyflavor
initions, and potential systematic uncertainties espe-
mysteriesthatcanonlyberesolvedindedicatedflavor
cially at startup. Of particular gravity is the devel-
experiments, many of which can only be performed at
opment of methods for extracting backgrounds and
LHCb [12],[13].
particle identification efficiencies from data wherever
possible,andthedefinitionoftriggerpaths(forasum-
mary of the status of trigger at the ATLAS and CMS
2.2 Outline of work towards early discoveries
experiments see [15]) and datasets needed for these
measurements.
Thepreparatory/readinessworkonearlysypersymme-
Both experiments are also carrying out detailed
trytargetingdiscoveriesatATLAScanbesummarized
studies aiming at non-supersymmetric exotic model
as follows:
signatures and searches.
– Data-drivenEstimationofZ/W backgroundtoSUSY
– Data-drivenEstimationoftopbackgroundtoSUSY
– Data-drivenEstimationofQCDbackgroundtoSUSY3 Discovery signatures
– EstimationofHeavyFlavorbackgroundsandasso-
ciated systematic TocomplywiththemeasuredprotonlifetimeO(1033yrs),
– Searches and inclusive studies for SUSY events a what seems to be ad-hoc symmetry is introduced
– Exclusive measurements for SUSY events to generic minimal supersymmetric models: R-parity,
– Gaugino direct production R = (−1)3(B−L)+2s, where for each particle s is the
– Studies for gauge-mediated SUSY spin,andBandLaretherespectivebaryonandlepton
assignments. The consequence of R-parity conserva-
Similarly the corresponding CMS program of work is
tionisastablelightestsupersymmetricparticle(LSP)
organized as follows:
that in most of the models is weakly interacting and
– Leptonic searches (MSSM template) provides a fair candidate for a component of the ob-
– Search for SUSY in ≥1 lepton+Emiss + jets at served dark matter in the universe. Due to the pair
T
14 TeV in the electron and muon channels (O(100 of LSPs a characteristic ensemble of signatures con-
pb−1)). tains large missing energy along with high number of
– indileptonpairs+Emiss+jetsat14TeVintheelec- jets and leptons. I will highlight some important as-
T
tron and muon channels (O(100 pb−1)). pectsofanalysesrelatedtothis“vanilla”typeofSUSY
– Search forSUSYin trileptons+ jetsat14 TeV.(1 searches in what follows. Signatures and searches as-
fb−1). sociated with GMSB or split-SUSY frameworks are
– Hadronic searches (MSSM template) reviewed in this meeting and summarized in [16] [17].
– Search for SUSY in 0 lepton + Emiss + jets at 14
T
TeV (O(100) pb−1).
– in b¯b + ETmiss + jets at 14 TeV (O(100) pb−1). 3.1 All-hadronic final states with large missing
– HeavyStableChargedParticlesandphotonicsearchesenergy
(GMSB template)
– Search and reconstruction of heavy stable charged Thecanonicalsearchanddiscoveryofgluinosandsquarks
particles at 14 TeV using TOF and dE/dx (500 isusingthelargemissingtransverseenergyplusmulti-
pb−1, model dependent).
jetsignature.Thelargemissingenergyoriginatesfrom
– SearchforGMSBusingpromptphotonsat14TeV
the two LSPs in the final states of the squark and
(500 pb−1).
gluino decays. The three or more hadronic jets result
To orient ourselves in the vast theoretical parame- from the hadronic decays of the q˜and/or g˜. Such an
ter space, we expect an iterative process of investiga- event display at the CMS detector is shown in Fig-
tive work once the data show excesses that can be ure 1. The search proceeds in a dataset triggered by
briefly outlined as follows ([14]): missingenergyandjets,alegentarilynotoriousdataset
in hadron colliders plagued by all types of instrumen-
– choose well-defined inclusive signatures tal and spurious backgrounds. Clean-up methods that
– extractsomeconstraintsonmasses,couplings,spin invoke the event electromagnetic fraction and event
from decay kinematics and rates charged fraction as first designed at the Tevatron [18]
Maria [email protected]
jetsandW(→τν)+≥2jets(thethirdjetoriginating
fromthehadronicτ decay)processes.Additionalresid-
ualcontributionisexpectedalsofromW(→µν), eν+≥3
jets. Both ATLAS and CMS are designing a compre-
hensive normalization program that relies on the Z +
multijet data (ATLAS also using the W+jets data)
to accurately estimate the W and Z+multijet back-
ground contribution in a large Emiss plus multijet
T
search.
The aim is to normalize the Monte Carlo predic-
tions for events with ≥ 3 jets and Z boson P > 200
T
GeV to the observed Z(→ µµ)+ 2 jets data sample
( where Z boson P > 200 GeV ) via the measured
T
R= dNevents ratio.
dNjets
As an example the Z →µµ +≥ 2 jets with Z >
PT
200 GeV is used as the “candle” data sample. The
Fig. 1. Event display of SUSY candidate event that sur-
selectedcandlesampledimuoninvariantmassisshown
vives the requirements of the CMS multijet+missing en-
inFigure3overlaidwiththeoneusingtheMonteCarlo
ergy analysis. The three highest E jets are 330, 140 and
T truth. Both the muon and electron decays of the Z
60 GeV while the missing transverse energy is 360 GeV.
will be used as the standardizable candle, but for the
(left)Legoη−φcalorimeterdisplay,thethreeleadingjets
purposes of demonstrating the method, the Z muon
arecolorcodedred-yellow-green,whilethemissingenergy
φisindicatedwiththeredline(right)transversex−yview, decays are chosen. Since the rudimentary calorimetric
showsrelativedepositionsofthejetsinthecalorimetersys- missingtransverseenergyisused(asislikelytobethe
tems as well as the reconstructed tracks and the missing case at the start-up of the experiment), the shape of
energy vector direction. the Emiss distribution of the measured the Z → µµ
T
+≥ 2 jet events will be very close to the shape of the
invisible Z → νν +≥ 2 jet events as shown in Figure
are also employed here - the final demonstration of 2.
theireffectivenessisunderstudywiththedetailedsim-
ulation of beam halo and cosmic events for example,
wherethetechniquesprovedtobeparticularlyefficient
at the Tevatron. Z-candle normalization, Emiss>200 GeV
T
tehrgeyDSpuMleusbthajeectksvgerdroayutnah-disgathmoQpalCelaDirsgpderoommdiiusnscaitntieogdntbrcayrnoQssvsCesrDescepteironon-- miss dET103 ZZ((-->>!!!!))++ >>==22jj ((Ztim-taegs dtaagta e)fficiency)
duction. The observed missing transverse energy in dN/ Z(->!!)+ >=2j (directly normalized to data)
QCD jet production is largely a result of jet mismea- 102
surements and detector resolution. Methods to elim-
inate QCD events based on angular correlations be-
tweenthejetsandthemissingenergyareemployedas
10
summarizedin[19]andtheeffectsofthejetresolution
on the tails of the missing energy distribution at [20]
and [21].
1
3.1.1 “Standard Candle” Calibration 200 300 400 500 600 700 800 900 1000
Emiss (GeV)
T
The so-called “standard candle calibration” methods
are pivotal in extracting the Standard Model back- Fig. 2. Emiss in Z → µµ + ≥ 2 jets candle sample and
T
ground normalization and shapes from the data, in normalized Emiss in Z →νν¯ + ≥ 2 jets sample.
T
particular with the early data 1. They have also been
shown to provide robust predictions in searches at the
Tevatron[18].InwhatfollowsIdiscussindetailama- The ratio ρ ≡ σ(pp→W(→µ(e)ν)+jets) will be
jor standard model candle, the Z0 boson. σ(pp→Z(→µ+µ−)(e+e−)+jets)
used to normalize the W+jets Monte Carlo predic-
Eventswithlargemissingtransverseenergyand≥3
tions.Assumingleptonuniversality,thepredictionsfor
jetsinthefinalstateareexpectedfromZ(→νν¯)+≥3
the number of events with ≥ 2– and ≥ 3–jets from
1 Becauseoftheirextremebrightness,typeIasupernovae W and Z production and decays to all flavors will be
havebecomepartofthecosmologicaltoolkitas”standard normalized to the Z(→ µ+µ−)+ ≥ 2 jets data. By
candles”usedtomeasuredistancestogalaxies;weborrow normalizingtheMCpredictionstodatasystematicef-
thenomenclaturewhenusingcleanstandardmodelsignals fects in particular at the early data taking stages can
to normalize background predictions to new physics. be ameliorated.
Maria Plenary
reason and aim of each selection step. Notice that al-
thoughtheanalysisisinclusiveweintroduceanumber
of steps targeting the cleanup of the dataset. These
steps (e.g Event Electromagnetic Fraction (EEMF),
Event Charged Fraction (ECHF)) are more than 90%
efficientintheMonteCarlostudiesbothforthesignal
andthebackgroundsbuttheareexpectedtoeliminate
instrumentalspuriousbackgroundsintherealdata.To
reduce the large Standard Model background contri-
bution mainly from W(→ (cid:96)ν)+jets, Z(→ (cid:96)(cid:96))+jets
and tt¯production and decays an indirect lepton veto
(ILV)schemeisdesignedthatusesthetrackerandthe
calorimeter. The aim of the ILV is twofold: a) to re-
tainlargesignalefficiencyb)toachievelargerejection
of the W,Z,tt¯backgrounds as shown in table 2. The
finalsignalandbackgroundyieldfor1fb−1 isgivenin
Fig. 3. Reconstructed and generator level Z dimuon in- table 3.
variant mass for Z → µµ + ≥ 2 jets and Emiss > 200
T
GeV.
Table 1. The Emiss + ≥ 3 jets SUSY search analysis
path.H =(cid:80)4 pTi +Emiss,fortheeventelectromagnetic
While the Z boson provides a very clean normal- T i=2 T T
andchargedfractionvariablesaswellastheindirectlepton
ization candle both ATLAS and CMS are designing
veto see [21], [23] .
the strategy for the extraction of the top background
at start-up also using the data and not relying on the Requirement Remark
Level1 L1triggerefficiency
Monte Carlo predictions. The top (see e.g. in [19]) as parameterization
wellastheW providelesscleanstandardcandles(due HLT,ETmiss>200GeV trigger/signalsignature
primaryvertex(PV)≥1 primarycleanup
toambiguitiesintheirmassreconstruction)butatthe EEMF≥0.175,ECHF≥0.1 primarycleanup
LHC their production rate is very high and their role Nj≥3,|ηd1j|<1.7 signalsignature
in the discovery plan will be crucial. In all cases the δφmin(ETmiss−jet)≥0.3rad,
R1,R2>0.5rad,
tails of the Standard Model processes such as W, Z, δφ(ETmiss−j(2))>20◦ QCDrejection
and top QCD associated production, will be enriched Isoltrk=0, ILV(I)
with SUSY signal events and the full standard can- EMF(j1),EMF(j2)<0.9 WILV/Z(/ItI)t¯,rejection
dle program needs to demonstrate robustness against ET,j(1)>180GeV,ET,j(2)>110GeV,
normalizingawaytheprobablesignal.Thecaveatsand HT >500GeV S/Boptimization
SUSYLM1signalefficiency13%
alerts on QCD associated production at the LHC and
the use of the predictions are discussed extensively in
the plenary talk and corresponding work of Michelan-
gelo Mangano [22]. In Figure 4 the results are shown for the inclusive
all-hadronic Emiss+≥3 jets search at CMS (top), the
T
all hadronic Emiss+≥4 jets search at ATLAS (bottom
T
3.1.2 Analysis paths for all-hadronic searches left),andtheEmiss+≥4jets+1isolatedleptonsearch
T
at ATLAS (bottom right) for 1 fb−1.
An ATLAS all-hadronic analysis path proceeds as fol- Due to the QCD Monte Carlo limited statistics to
lows: derive the QCD background component the analysis
path is followed without the topological QCD clean-
– N ≥4,
jet up requirements and ILV requirements. The estimate
– pJ1 >100 GeV/c & pJ4 >50 GeV/c,
T T isbasedonfactorizingtheclean-upandILVefficiency,
– S >0.2,
T assuming them uncorrelated with the rest of the anal-
– Emiss >100 GeV & Emiss >0.2×M ,
T T eff ysis requirements and using a parameterization of it
where Njet, pJT1(4), ST and Meff are the number as a function of the ETmiss for the large ETmiss tails.
of jets , the transverse momentum of first (fourth)
leading jet, the transverse sphericity and the effec-
tive mass, respectively. The effective mass is defined 3.2 Leptonic signatures with large missing energy
as M = (cid:80)i≤4pi + Emiss, where pi is the trans-
eff i=0 T T T
versemomentumofi-thleadingjet.Theanalysispath Signatures with leptons, jets and missing energy pro-
that includes leptons in the final state is similar with vide both discovery and characterization channels for
theadditionalselectionofeventsrequiringoneisolated SUSY.Leptonsareproducedinthedecaysofcharginos
lepton with p larger than 20 GeV and the transverse andneutralinos;theirkinematicandtopologicalchar-
T
mass M >100 GeV. acteristics as well as their mutliplicities including fla-
T
A selection path for the all-hadronic CMS analy- vorandchargecanpointtowardstheproductiontypes
sis is shown in Table 1 with a remark indicating the and rates (i.e. mass hierarchies) of the squarks and
Maria [email protected]
miss dN/dE11T0023 CMS EmTiss + multijetmZZ+mZZ+mZZ+mZZ+sQQQQiiiiiiiiSnnSnnSnnSnn,CCCC vvvvvvvvUUUU1++++++++DDDDGGGGtttttttt ttttttttfRRRR++++bEEEEAAAA-WWWW 1LLLLMMMMKKKK1111 dN/dHT110023 CMS EmTiss + multijetmZZ+smZZ+QiimZZ+mZZ+Snn,QiiQiiQiiC vvSnnUSnnSnn1++CvvCUvvDCvvUGU++tt++ ++DttDGDGGfR+ttttttttttbttR+ERA+R+EWA-EE AA1LW WW MKLLLMKMKMK1111 ssisitgadngeaem.tuIornnessFttriogautbirneegr5etnhadenerkAeindTeLumAsaeSftuicllobwedeygmoenaosdsftSthhUeeSdYdisiclesotpvutedornyy
invariant mass M . The edge is a measure of mass
(cid:96)(cid:96)
10
10 differences between the sparticles that are involved
1 1 in the decay (here the χ˜02,(cid:96)˜R and χ˜01 with M(cid:96)m(cid:96)ax =
(cid:114) (cid:114)
10-1 10-1 M(χ˜0) 1− M2((cid:96)˜R) 1− M2(χ˜01)).Similaredgesareshown
200 400 600 800 1000 1200 E1mT4is0s 0(GeV1)6 00 600 800100012001400160018002000220024H00T 2(G60e0V2)8 0 0 2 M2(χ˜02) M2((cid:96)˜R)
in Figure 7 from CMS and ATLAS in different parts
ATLAS Preliminary SUSY (SU3) 102 ATLAS Preliminary SUSY (SU3) of the mSUGRA parameter space.
103 Attblla brackgrounds Attblla bra(c!k>glnrolnu)nds
Z ttbar(!>lnqq)
W 10 W
102 QCD
1
10
10!1
1
500 1000 1500 2000 2500 500 1000 1500 2000 2500
Meff (GeV) Meff (GeV)
Fig. 4. (top) Emiss and H distributions in the all-
T T
hadronic CMS analysis. (bottom) The M distributions
eff
for no-lepton (left) and single lepton (right ) signatures in
ATLAS. All for integrated luminosity of 1fb−1.
Table 2. Cumulative selection efficiency after each
requirement in the Emiss+multijets analysis path for
T
major Standard Model backgrounds. (EWK refers to
W/Z,WW/ZZ/ZW).
Fig. 5. The dilepton invariant mass distribution for a
Cut/Sample Signal tt¯ Z(→νν¯)+jets EWK+jets full simulation sample of an ATLAS low mass benchmark
All(%) 100 100 100 100 SUSY point with an integrated luminosity of 350 pb−1. A
Level-1 92 40 99 57
triangular function convoluted with a Gaussian is used in
HLT 54 0.57 54 0.9
PV 53.8 0.56 53 0.9 the fit to estimate the edge position. Note that the signal
N|ηj1s≥t,3j≥1.7 3349 00..3306 43 00..017 significanceiswellover5σ significancewithonly100pb−1
d
EEMF≥0.175 34 0.30 3 0.07 [24].
ECHF≥0.1 33.5 0.29 3 0.06
QCDangular 26 0.17 2.5 0.04
Isoleadtrk=0 23 0.09 2.3 0.02
EMF(j1), Note that top, bottom, Z and W in the decays of
EMF(j2)≥0.9 22 0.086 2.2 0.02 sparticles(i.e.non-directStandardModelproduction)
PT,1>180GeV,
PT,2>110GeV 14 0.015 0.5 0.003 inleptonicfinalstatescanalsopointtowardsratesand
HT >500GeV 13 0.01 0.4 0.002 masshierarchiesoftheSUSY(orotherBSM)particles
1/fb
produced.
HT >500GeV 6319 53.9 48 33
Table 3. All-hadronic selected low mass SUSY and Stan- 4 The LHC SUSY Search, Orientation and
dard Model background events for 1 fb−1 from CMS Navigation Tool-Kit
Signal (LM1) 6319
tt¯/single t 56.5 4.1 Excesses as a function of luminosity
Z(→νν¯)+ jets 48
(W/Z,WW/ZZ/ZW) + jets 33 The CMS and ATLAS collaborations have published
QCD 107 their physics performance reviews [23], [25]. A rough
summaryofthe5σ reachandthecorrespondingchan-
nels/analyses are given below (using the results from
the most recent available results) in a format of what
gluinos and the composition of the LSP. Tradition- apublicationmightlooklikeif/whensuchanexcessis
ally invariant masses that involve dileptons and lep- observed 2:
tons+jets have been used at the LHC for the mass re- 2 Thereisalevelofabsurdityinthelistingaspresented
construction using large integrated luminosity. These
here, however it is illustrative of the daunting task that
studies are currently being worked for the early data the experiments will be faced with when trying to inter-
and additional measurables are being introduced. The pretandcross-interpretthepossiblevarietyofsignalsthey
measurement and understanding of the trigger, lep- might observe, as these emerge; note that the luminosity
ton identification efficiencies and acceptance as well valuesinparenthesisareroundedforthepurposesofillus-
as fake rates are prerequisites for the lepton involving trationandcalculatedwithassumptionsonthesystematics
Maria Plenary
– Search for SUSY (Evidence for excess) in ≥1 lepton
+ Emiss + jets at 14 TeV in the electron and muon
T
channels (100 pb−1).
– SearchforSUSY(Evidenceforexcess)inoppositesign
dileptonpairs+Emiss +jetsat14TeVintheelectron
T
and muon channels (20 pb−1)
– Search for SUSY (Evidence for excess) in same-sign
dileptonpairs+Emiss +jetsat14TeVintheelectron
T
and muon channels (200 pb−1)
– Search for SUSY (Evidence for excess) in Z0 leptonic
decays+ Emiss + jets at 14 TeV in the electron and
T
muon channels (100 pb−1)
– Search for LVF SUSY (Evidence for excess) in e+µ
final state at 14 TeV (500 pb−1) Fig. 6. Just like decoding DNA we have to decode the
– Search for SUSY (Evidence for excess) in trileptons at signalswewillobserve.Andwedoexpectmoresimilarities
14 TeV. (∼fb−1) than differences, so fast discrimination will require smart
– Search for SUSY (Evidence for excess) in 0 lepton + and simple measurements
Emiss+ jets at 14 TeV (10 pb−1)
T
– SearchforSUSY(Evidenceforexcess)inb¯b+Emiss +
T
jets at 14 TeV (100 pb−1) set of possible reconstructed mass edges and “bumps”
– Search for SUSY (Evidence for excess)in top hadronic that might emerge with early data at ATLAS and
decays+ ETmiss at 14 TeV (200 pb−1) CMS.
– SearchforSUSY(Evidenceforexcess)inopposite-sign In figure 8 I give the recoil mass spectrum associ-
ditau + ETmiss at 14 TeV (200 pb−1) ated with the then (1976) newly discovered charmed
– SearchforGMSB(Evidenceforexcess)inpromptpho- mesonsine+e−annihilationatSPEAR[34].Thestudy,
ton final states at 14 TeV (500 pb−1)
interpretationandpredictionsbasedonthesemeasure-
– SearchforGMSB(Evidenceforexcess)innon-pointing
ments were published concurrently [35] and involved
photons at 14 TeV (1 fb −1)
threshold, form factor, spin-effects and mass splitting
– Searchandreconstructionofheavystablechargedpar-
analysis. The interpretation template then was the
ticles at 14 TeV using TOF and dE/dx (500 pb−1)
charm hypothesis. As Michelangelo Mangano pointed
– ....
out this is possibly the closest Standard Model ex-
Grouping the signatures for the sake of this dis- ample that could illustrate the least we foresee to be
cussion we still have a large listing of probable “fast” facedwithregardingdiscoveriesandpatternstobein-
signals: terpreted with the early data at the LHC. One of the
difficultiesnowisthattheinterpretationtemplatesare
– canonical inclusive
infinite.
– jets+ Emiss (no lepton)
T Nevertheless,thestudyofthequestionsofthetype
– jets+ (cid:96) + Emiss
T that follows could point us to a direction:
– same-sign dilepton + Emiss
T
– opposite-signsameflavordielectronanddimuon – if excess of SS dileptons → ?
+ Emiss – if ++/−− =2 → ?
T
– higher reco object inclusive – if excess if OS dileptons → ?
– Z + Emiss – if triangle in dilepton invariant mass → ?
T
– t hadronic + Emiss – if double triangle → ?
T
– h0(b¯b) + Emiss – if no triangle → ?
T
– if Z0 and no triangle → ?
The matter in question is how exactly do we dis- – if Z0 and triangle → ?
entangle the emergent patterns in the observations
– jetandleptonobjectcountingandratios(i.e.3j/4j/5j/6j,
(if/whenexcessesareobserved)inordertogetadirec-
1(cid:96)/2(cid:96)/3(cid:96)/4(cid:96)), → ?
tion towards the underlying mechanisms beyond the
– ...
standardmodel.Iliketodepictthisgraphicallyinthe
form of Figure 6.
The question is synonymous to the “inverse LHC
5 Conluding Remarks
problem”attackedwith“footprint”approaches[26],MAR-
MOSETs [27] and other strategies that include full-
Ourcurrentandextrapolatedstatus-of-beingasafield
event harvest [28], multivariate sophisticates analyses
is summarized very eloquently in this meeting by the
withdecisiontrees[29],spin-prints[30],[31])aswellas
introductory talk “Anticipating a New Golden Age”
systematic understanding of the SUSY available kine-
of Frank Wilczek [36]. I would like to make a few very
matics and topologies [32], and defining a strategy for
obvious comments here.
distinguishing “look-alike” variations within SUSY it-
1. Althoughwecannotpredicttheexperimentaldata
self and other frameworks [33]. I give in Figure 7 a
at the LHC we do build a strong preparatory pro-
-sometimesconservativeandalwaysreferringtoanunder- gramofanalysisstrategiesforthepotentialdiscov-
standing of the detector with 1 fb−1. ery physics search, navigation and orientation.
Maria [email protected]
s 45
r CMS
ai
p 40
n
pto 35 LM1 1 fb-1
of le 30 ttbar
r 25
e
b
m 20
u
n 15
10
5
0
0 20 40 60 80 100 120 140 160 180 200
M(l+l-) (GeV/c2)
s 1 fb-1
nt Fig. 8. Recoil spectra for combination in the Kπ and
e
vE25 Signal + Background Kπππ peaks from [34].
h->bb + correct jet pairing
other SUSY event
20
SM background
fit result be directly measured, it must be calculated and
background fit function
15 this requires knowledge of its mass and its inter-
actions that are relevant to how it annihilates in
10 the early universe. Both the cosmology standard
modelandallthebeyondtheparticlephysicsstan-
dard model scenarios have large “terra incognita”
5
sectors: the exercise of constraining cosmology us-
ing assumed beyond the standard model physics
00
5500 110000 115500 220000 225500 330000 335500 440000 450 500 frameworks (and data from direct DM searches)
Min v(GeV) and vice-versa will be a major part of the physics
program at the LHC (see also the DM discussion
Fig. 7. Howwillweusedifferentobservationstonavigate in [36]).
the parameter space at start-up? What are the optimal 4. Basedonourcurrentknowledge,supersymmetryis
measurables at start-up that will help piece-together a di- the most plausible theory to extend the Standard
rection? (top) dilepton invariant mass from a CMS SUSY Model in the TeV scale and should have already
benchmark point analysis, (middle) similar from ATLAS, been observed in the LEP, Tevatron or low energy
(bottom)b¯binvariantmassfromaCMSSUSYbenchmark
data. The searches at the LHC use various sub-
point analysis.
sets of supersymmetric points in the vast parame-
terspaceastemplatestoprovideasignaturespace
that is well studied in preparation for the much
2. Within this preparatory program we observe anew
anticipated confusing multitude of SUSY-mutant
the strong concilience between theory and experi-
features in the data (as opposed to studying a few
ment.
points in the mSUGRA 3 parameter space).
3. Theemergentconfluencebetweencosmological–es-
pecially on the dark matter, and particle physics
data presents us with a real reciprocity. The relic 3 Note that using the formulation of [4] mSUGRA is
density for a given dark matter candidate cannot equivalenttotheconstrainedCMSSMmodel,seealso[37].
Maria Plenary
5. Finally I would like to close with a few words of 21. T. Yetkin and M. Spiropulu, Acta Phys. Polon. B38,
caution: In my talk at this meeting I showed how 661 (2007).
thedifferentmodernSUSYspectracalculatorsthat 22. Michelangelo Mangano, Standard Model Back-
we use in the LHC experiments give different re- gounds to SUSY searches, SUSY07 Karl-
sults in particular corners of the parameter space sruhe,http://indico.cern.ch/getFile.py/access
and for small variations of standard model input ?contribId= 81&sessionId=276&resId=0
values (I used the top mass as an example). While &materialId=slides&confId=6210 .
thereisalotofprogress,thereisalsoalotofwork 23. G. L. Bayatian et al., J. Phys. G34, 995 (2007).
24. N.Ozturk,SUSYParametersDeterminationwithAT-
remainingforaconsistentimplementationofSUSY
LAS, 2007, arXiv:0710.4546 [hep-ph].
mutli-bodydecaysandSUSYQCDassociatedpro-
25. ATLAS Collaboration, CERN-LHCC-99-15 (1999) ,
duction. Similar caution was raised by Michelan-
995 (2008).
gelo Mangano [22] on most all the standard model
26. N. Arkani-Hamed, G. L. Kane, J. Thaler, and L.-T.
QCD associated production. We will use the data
Wang, JHEP 08, 070 (2006), hep-ph/0512190.
tocalibratethestandardmodelbutitisimportant
27. N.Arkani-Hamedetal.,MARMOSET:ThePathfrom
todesignexactlyhowwewilldothisgiventhatthe
LHC Data to the New Standard Model via On-Shell
data will be contaminated by discoveries.
Effective Theories, 2007, hep-ph/0703088.
28. H.-C.Cheng,J.F.Gunion,Z.Han,G.Marandella,and
B.McElrath,MassDeterminationinSUSY-likeEvents
Acknowledgements with Missing Energy, 2007, arXiv:0707.0030 [hep-ph].
29. J. Conrad and F. Tegenfeldt, JHEP 07, 040 (2006),
I would like to thank especially Wim De Boer, Luc hep-ph/0605106.
Pape,ShojiAsai,DavidCostanzo,MichelangeloMangano3,0. A. J. Barr, Phys. Lett. B596, 205 (2004), hep-
ph/0405052.
Gordy Kane, Joe Lykken and the CMS and ATLAS
31. A. J. Barr, JHEP 02, 042 (2006), hep-ph/0511115.
collaborations.
32. L. Pape and F. Moortgat, in preparation.
33. J. Hubisz et al., in preparation.
34. G. Goldhaber et al., Phys. Rev. Lett. 37 (1976).
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