SUSY Searches at ATLAS

0.19 MB·English

by  Paul de Jong

SUSY Searches at ATLAS
PauldeJong1,a,onbehalfoftheATLASCollaboration
Nikhef,P.O.Box41882,NL-1009DBAmsterdam
2 Abstract. RecentresultsofsearchesforsupersymmetrybytheATLAScollaborationinupto2fb 1of √s=7
−
1 TeV ppcollisionsattheLHCarereported.
0
2

n 1 Introduction MSUGRA/CMSSM: tanβ = 10, A = 0, µ>0 Lint = 1.34 fb-1
a 0
J eV]550 ATLAS obs. CLs 95% C.L. limit
22 Dhausedtiosctohveehryigphocteennttirael-ofof-rmneawssheenaevrgyypoarfti7clTeesVb,etyhoenLdHthCe [Gm1/2500 MMuullttiijjeettss pplluuss EEmTmTiissss CCoommbbiinneedd 2eexx0pp1..1 Cl ≥im2L,si3t 9,±451 %j σe tCs .pLl.u lsim Eimtiss
] Tpaervtaictruolnarlfimoritpsaretvicelneswwitihthlictotlleoulurmchinarogseit,ys.uTchhiasshsoqludasrkins 450 q (~1400) CLELsP 9 25 %∼χ ± C.L. limit T
p-ex atsoenndthsigetlievuxiitncyeolsalelisnnotsleuuxpmiesirtnssoyfsmoitrmyepeleetrcryftro(orSwmUeaSankYce)por[o1fd]th.ueHctLoioHwnCevoiefnrc,2hd0au1re1-, 345000 q ~(1000) ~g (1000) DTCh0De F~go, ~ rg~qe,,~qt i1t,ca tanalβlny=β e=3x,5 cµ, lµu<d<0e,0 d2, .21 ffbb-1-1
e ginosandneutralinos,the supersymmetricpartnersofthe
h electroweak gauge bosons and the Higgs boson. In this 300
1 [ dpoercsuymmemnte,tarynwumithbeurpotfor2esfubl−ts1ooffALTHLCApSpsdeaartachaets√fosr=su7- 250q~ (600) ~g (800)
v TeVaresummarized.Sincenoneoftheanalyseshaveob- 200 ~g (600)
8 servedanyexcessabovetheStandardModelexpectation,
4 limits on SUSY parameters or masses of SUSY particles 150
5
are set. Itis, however,importantto considercarefullythe
500 1000 1500 2000 2500 3000 3500
4
assumptionsmadein eachofthe limits,andthe truecon- m [GeV]
. 0
1 straintsthattheyimposeonsupersymmetry.
0 Fig. 1. Exclusion contours in the MSUGRA/CMSSM m -m
0 1/2
2 planefor A = 0,tanβ = 10andµ > 0,arisingfromtheanal-
0
1 ysiswith 2, 3or 4jetsplusmissingmomentum,andthe
: 2 Searches with jets and missing multijetsp≥lusm≥issing≥momentumanalysis.
v
momentum
i
X
r AssumingconservationofR-parity,thelightestsupersym- inasemi-data-drivenway,usingcontrolregionsincombi-
a
metricparticle(LSP)isstableandweaklyinteracting,and nationwithatransferfactorobtainedfromsimulation.
will typically escape detection. If the primary produced The results are interpreted in the MSUGRA/CMSSM
particles are squarks or gluinos (and assuming a negligi- model,andinparticularaslimitsintheplanespannedby
blelifetimeoftheseparticles),thiswillleadtofinalstates the common scalar mass parameter at the GUT scale m0
with energeticjetsandsignificantmissingtransversemo- andthecommongauginomassparameterattheGUTscale
mentum. m1/2, for values of the commontrilinear couplingparam-
ATLAScarriesoutanalyseswithaleptonveto[2],re- eter A0 = 0, Higgs mixingparameter µ > 0, and ratio of
quiring one isolated lepton [3], or requiring two or more the vacuumexpectationvaluesof the two Higgsdoublets
leptons [4]. In addition, a dedicated search is performed tanβ=10.Figure1showstheresultsfortheanalyseswith
foreventswithhighjetmultiplicity[5].Datasamplescor- 2, 3 or 4 jets plus missing momentum, and the
≥ ≥ ≥
responding to luminosities between 1.0 and 1.3 fb 1 are multijets plus missing momentum analysis. For a choice
−
used. Events are triggered either on the presence of a jet of parametersleadingto equalsquarkandgluinomasses,
plus large missing momentum, or on the presence of at squarkandgluinomassesbelowapproximately1TeVare
leastonehigh-p lepton.Backgroundstothesearchesarise excluded. The 1-lepton and 2-lepton results are less con-
T
fromStandardModelprocessessuchasvectorbosonpro- straininginMSUGRA/CMSSMforthischoiceofparam-
ductionplusjets (W + jets, Z + jets), top quarkpair pro- eters,buttheseanalysesarecomplementary,andtherefore
duction and single top production,QCD multijet produc- nolessimportant.
tion, and diboson production.Backgroundsare estimated The search with two isolated opposite-chargeleptons
isalsointerpretedintheframeworkofminimalgaugeme-
a e-mail:[email protected] diatedsupersymmetrybreaking(GMSB),asshowninFig-
EPJWebofConferences
GMSB: M =250TeV, N=3, sign(µ) = +, C =1 Squark-gluino-neutralino model
βn 50 mes 5 grav V]2000 ATLAS Preliminary
ta ATLAS Preliminary Observed 95% CL Ge 0 lepton 2011 combined
3400 Theory excl. Lint = 1.0MOLLE4EExP efpPPdAbe iL99a-c1 55nt,9e%% 5e d% x CClspi mLLCe= cLi((7 tt∼~τe .± 1 RT)9 )15eσ%V CL ark mass [11570500 ∫ L dt = 1.04EEOO xxfbbbppss-..1.., mmmmsLLLLSS=SSPPPP7 == ==T e0101V 9 9GG55e e GGVVeeVV
OS combined EmTiss + 3 jets qu EOxbps.. mmLSP == 339955 GGeeVV
s1250 LSP
1200 χ∼10 ∼τC1oNLSP ~ lR 1705000 Tevatron, Run I CDF, Run II D0, Run II σσSSUUSSYY == 00..10 1p pbb
10 20 30 40 50 60 Λ [TeV7]0 σSUSY = 1 pb
500
Fig. 2. Exclusion contours in the GMSB Λ-tanβ plane, for σSUSY = 10 pb
M =250TeV,N =3andµ>0,resultingfromtheopposite- 250
chmaregseleptonanalys5is. LEP2 ~q
0
0 250 500 750 1000 1250 1500 1750 2000
gluino mass [GeV]
ure2[6].Assumingamessengermassscale M of250
mes
Fig.3. Exclusioncontours inthesquark-gluino massplane, for
TeV, 3 generations of messengers (N = 3) and µ > 0,
5
three values of the LSP mass, using the simplified model de-
limitsaresetontheeffectiveSUSY breakingscaleΛ and
scribedinthetext.
ontanβ.TheselimitssignificantlyimproveontheLEPre-
sults.
∼∼
Direct decay, ~g~g ⇒ qqqqχ0χ0
V]1000 11 102 b]
3 Simplified model interpretation mass [Ge 890000 ∫0A0 LllTee dppLttt oo=Ann 1 22S.000411 11 Pf bcc-r1oo,e mmlsbbi=miinn7ee TiddneVary % C.L. [p
ATLAShasfounditusefultonotonlyinterprettheresults P CLs observed 95% C.L. limit 10 95
ienlscaosnssutrmaiinnegdsmpeocdifielcs,pbruotdaulcstoioinnatenrdmdseocfasyimmpoldifieesd[7m].oIdn- LS 670000 CExLps emceteddia lnim eitx ±p1e cσted limit ded at
seulsclhikseimMpSliUfiGedRmA/oCdMelsS,StMheocroGnsMtrSaiBntasreimrepllaixededb,yleamvoindg- 500 ~g LS P exclu
more freedom for variation of particle masses and decay 400 1 BR)
modes.Interpretationsinsimplifiedmodelsthusshowbet- ×
300 σ
terthelimitationsoftheanalysesasafunctionoftherel- (
evantkinematicvariables,andaidindrawingconclusions 200
10-1
fromtheresults.
100
Inclusivesearchresultswithjetsandmissingmomen-
tumareinterpretedusingsimplifiedmodelswitheitherpair 0
300 400 500 600 700 800 900 1000
productionofsquarksorofgluinos,orproductionofsquark-
gluino mass [GeV]
gluinopairs.Directsquarkdecays(q˜ qχ˜0)ordirectglu-
1
ino decays (g˜ qq¯χ˜0) are dominan→tif all other particle Fig.4.Crosssectionlimitsandexclusioncontoursinthegluino-
masses have m→ulti-TeV1 values, so that those do not play neutralinomassplane,fordirectgluinodecays,g˜ →qq¯χ˜01,asob-
tainedbytheno-leptonanalysis.Allsquarkmassesareassumed
arole.Additionalcomplexitymaybebuiltin,forexample
byallowingone-stepdecaystointermediatecharginos,χ˜±, tobemulti-TeV,sothatonlygluinopairproductiontakesplace,
and thedirect decay isassumed tooccur with100% branching
orheavierneutralinos,χ˜0.
2 fraction.
Figure3showstheATLASresultsinterpretedinterms
of limits on (first and secondgeneration)squark and glu-
inomasses,forthreevaluesoftheLSP(χ˜0)mass,andas-
1 catethatmassesoffirstandsecondgenerationsquarksand
sumingthatallotherSUSYparticlesareverymassive[8].
ofgluinosmustbeaboveapproximately750GeV.Anim-
Furtherinterpretationsaredoneintermsoflimitsongluino
portant caveat in this interpretation is the fact that this is
massvsLSPmassassuminghighsquarkmasses,asshown
onlytrueforneutralinoLSPmassesbelowapproximately
for example in Figure 4 for direct decays, or in terms of
250GeV(asinMSUGRA/CMSSMforvaluesofm be-
1/2
limitsonsquarkmassvsLSPmassassuminghighgluino
low (600)GeV).ForhigherLSPmasses,thesquarkand
masses [3,8]. Figure 5 shows an example of limits in the O
gluinomasslimitsaresignificantlylessrestraining.Itwill
gluino-LSPmassplaneobtainedfromone-stepgluinode-
be a challengefor furtheranalysesto extendthe sensitiv-
cays,g˜ qq¯′χ˜±, χ˜± W(∗)χ˜01,bytheone-leptonanaly- ity of inclusive squark and gluino searches to the case of
→ →
sis.Thecharginomassinsuchdecaysisafreeparameter, heavyneutralinos.If the LSPis heavy,eventsare charac-
characterizedbyx=(mχ˜±−mχ˜01)/(mg˜−mχ˜01),andFigure5 terized by less energetic jets and less missing transverse
showsx=1/2asanexample. momentum.This will be more difficult to trigger on, and
The results of the inclusivejets plusmissing momen- lead to higherStandard Modelbackgroundsin the analy-
tumsearches,interpretedinthesesimplifiedmodels,indi- sis.
HadronColliderPhysicsSymposium2011
V] 800 b]
[GemLSP 670000 ~LgC1~gi-noS→t m=teqb p1qin .qD0aq4etWi cofbanW-y1,,χ∼ x01s=χ∼=0117/2 TeV ATLAS 102at 95% CL [p m [GeV]∼0χ1330500 ~b1-~b1C pDroFd 2u.c6ti5o nfb, -~b11→ b+∼χ01 C±CC LLL1sss σ EOE NxxbppLseeOeccr vttseeecddda lLLeLii immmuniiitttc (±(.9 9155 σ%% CC..LL..))
500 Observed 95% CL ded 250 D0 5.2 fb-1 ATLAS
340000 EExxppeecctteedd ±1σ 10 Section Exclu 125000 ~b →1 b ∼χ0 1forbidden ∫L dt = 2.05 fb-1, s = 7 TeV
1 s
s
200 Cro 100
Reference point
100
10-1 50
0
300 400 500 600 700 800 0
100 150 200 250 300 350 400 450
mgluino [GeV] m~ [GeV]
b
1
Fig.5.Crosssectionlimitsandexclusioncontoursinthegluino-
Fig. 6. Exclusion contour inthesbottom-neutralino mass plane
neutralino mass plane, for one-step gluino decays, g˜ qq¯′χ˜±, resultingfromtheanalysissearchingforsbottomquarkpairpro-
χ˜± → W(∗)χ˜01,asobtainedbytheone-leptonanalysis.→Onlyglu- duction,assumingsbottomtobottomplusneutralinodecay.
inopairproductionisconsidered,theone-stepgluinodecayisas-
sm4uamSsseUdisStcohYoacraaccuntredrwizintehda1bt0yu0x%ra=bl1rna/ne2cs(hsisenegtferxatc)t.ion,andthechargino [GeV]m~t1556050000~g-~g 1>A>+-== ~lTte -11~tpL tpbboAr--nottaa,dS gg4u,, c jmmePtitoeesrffnff e,>> ~g l66 i→00m00 ~t iGG1+neet,aVV ~tr1→y b+χ∼±1 OECCExxLLbppsss∫ eeoeeLccbxrdtvtpseeteee dd=drc vC AtA1eeTL.Tdd0sLL 3llAliiAim mmfSSbiiit t-t (1 (,3±3 515sσ p=pb7b--11 )T)eV
450
m(χ∼0) = 60 GeV , m(χ∼±) ≈ 2 m(χ∼0)
1 1 1
ItrmypaorretatnhtemfaocttivsatthioatnsSUfoSrYelemctirgohwteparko-vsicdaeleasnuapteurrsaylmsomlue-- 334050000 m(~q1,2) >> m(~g) ~g → ~tt1 forbidden
tion to the hierarchy problem by preventing “unnatural”
250
fine-tuning of the Higgs sector, and that the lightest sta-
bleSUSYparticleisanexcellentdarkmattercandidate.It 200 Reference point
isinstructivetoconsiderwhatsuchamotivationreallyre- 150
quiresfromSUSY:arelativelylighttopquarkpartner(the 300 350 400 450 500 550 600 650 700 750 800
stop, t˜) (and an associated sbottom-leftquark, b˜ ), a glu- mg~ [GeV]
L
inonotmuchheavierthanabout1.5TeVtokeepthestop Fig.7.Exclusioncontourinthegluino-stopmassplaneresulting
light (the stop receives radiative corrections from loops fromtheanalysissearchingfor stopquark production ingluino
liket˜ g˜t t˜),andelectroweakgauginosbelowtheTeV decays.Theassumptionsmadetoderivetheplotarelistedinthe
scale→[9].Th→erearenostrongconstraintsonfirstandsec- plot.
ondgenerationsquarksandsleptons;infactheavysquarks
andsleptonsmakeiteasierforSUSYtosatisfythestrong
constraintsfromflavourphysics.Motivatedbythese con- a neutralino (LSP) with a 100% branching fraction. Un-
siderations,ATLASexplicitlysearchesforthirdgeneration dertheseassumptions,sbottommassesupto390GeVare
squarksandforelectroweakgauginos. excludedforneutralinomassesbelow60GeV.
ATLAShassearchedforstopquarkproductioninglu-
ino decays [12] using an analysis requiring at least four
high-p jetsofwhichatleastoneshouldbeb-tagged,one
T
5 Stop and sbottomsearches
isolatedlepton,andsignificantmissingtransversemomen-
tum.Afterapplyingtheselectioncriteria,74eventsareob-
ATLAS has carried out a number of searches for super- servedin1.0fb−1ofdata,where55 14backgroundevents
±
symmetrywith b-taggedjets, which are sensitive to sbot- are expected from a data-driven estimation procedure, or
tom and stop quarks production, either direct, or in glu- 52 28 from Monte Carlo simulations. Since there is no
±
inodecays.Jetsaretaggedasoriginatingfromb-quarksby significant excess, limits are set in the gluino-stop mass
analgorithmthatexploitsbothtrackimpactparameterand plane,assumingthegluinotodecayasg˜ t˜t,andthestop
secondaryvertexinformation. quarktodecayast˜ bχ˜±1,asshowninF→igure7.
→
Directsbottompairproductionissearchedforinadata Inaddition,ATLAShassearchedforsbottomproduc-
samplecorrespondingto2fb 1 byrequiringtwob-tagged tionin gluinodecays,setting limitsinthegluino-sbottom
−
jetswith p > 130,50GeVandsignificantmissingtrans- massplaneandinthegluino-neutralinomassplane[13].
T
versemomentumofmorethan130GeV[10].Thefinaldis- Furthersearches for directstop quarkpair production
criminantistheboost-correctedcontransversemassm [11], areinprogress.Thesesearchesarechallengingduetothe
CT
andsignalregionswithm >100,150,200GeVarecon- similaritywiththetopquarkpairproductionfinalstatefor
CT
sidered.Noexcessesareobservedabovetheexpectedback- stop masses similar to the top mass, and due to the low
groundsoftop,W+heavyflavourandZ+heavyflavourpro- cross section for high stop masses. ATLAS has searched
duction.Figure6showstheresultinglimitsinthesbottom- forsignsofnewphenomenaintopquarkpaireventswith
neutralino mass plane, assuming sbottom quark pair pro- large missing transverse momentum [14]; such an analy-
ductionandsbottomquarkdecayintoabottomquarkplus sis is sensitive to pair production of massive partners of
EPJWebofConferences
m [GeV]~g111102000000GGM: bin±AAAo TTT1-LLLl iσAAAkeSSS nCCCeLLLussst oreoabxblpssineeeorcrvvt,eee tddda 9n995β55%%% = CCC2LLL, cllliiimmmτNiiitttL S(3P6 < pA b0.T-11)L mAmS [GeV]m∼0χ1330500 χ∼±1∫ mχ∼L∼χ02 ±1d →=t =m ~ lν1∼χ02. ~,0l lm,4 l~ lν∼,fν∼b ~=l-l1 , → m Ls Sl=νP7 +χ∼ T 011e l/Vl2 χ∼ (01m∼χ±1 - m∼χ01) 345345 % CL [pb]% CL [pb]
CMS observed 95% CL limit (35 pb-1) Observed 95% CL 22 9595
900 250 Expected at at
Expected ± 1 σ d d
800 ∫Ldt = 1.07 fb-1 200 ATLAS 11 cludeclude
700 xx
s = 7 TeV 150 n En E
600 oo
500 ~g NLSP 100 s Sectis Secti
400 200 400 600 800 1000 1200 50 CrosCros
mχ∼ [GeV] 0 150 200 250 300 350 00..22
m∼χ±,∼χ0 [GeV]
1 2
Fig.8.Exclusioncontourinthegluino-neutralinomassplanein
Fig. 9. Cross section limits and exclusion contours in the
thegeneralgaugemediation(GGM)model,assumingabino-like
chargino-neutralino massplane,resultingfromthesame-charge
neutralino,resultingfromthediphotonplusmissingmomentum
dilepton analysis. The interpretation is done in a simplified
analysis.
model,detailsaregivenintheplot.
the top quark, decaying to a top quark and a long-lived
undetected neutral particle. No excess above background selectioncriteriaonjetsandonthemissingtransversemo-
wasobserved,andlimitsonthecrosssectionforpairpro- mentum. For all signal regions, the observed event count
duction of top quark partners are set. These limits con- agreeswiththeexpectedbackground.Theanalysisselect-
strain fermionic exotic fourth generation quarks, but not ing same-chargeleptonspluslargemissing momentumis
yetscalarpartnersofthetopquark,suchasthestopquark. sensitive to electroweak gaugino production, and results
for this analysis are shown in Figure 9. The interpreta-
tionisdoneinasimplifiedmodelassumingchargino(χ˜±1)
6 Electroweakgaugino searches plusaheavierneutralino(χ˜0)production,anddecaytolep-
2
tonsandLSPsthroughintermediatesleptons.Undertheas-
Searchesforcharginosandneutralinosarecarriedoutvia sumptionofequalmassofχ˜±1 andχ˜02,limitsaresetinthe
amneanlytusmes,oofrfimnualltsilteaptetsoninsvpolluvsinmgipsshiontgonmsopmluesnmtuimss.ingmo- χ˜±1 −χ˜01massplane.
Ingaugemediationmodels,neutralinosdecaytograv-
itinosplusoneormorestandardmodelparticles,depend-
7 Specialfinal states
ing on the neutralinocomposition.For bino-likeneutrali-
nos, the final state consists of a pair of high-p photons
T ThenumberofdifferentfinalstatessensitivetoSUSYpro-
plusmissingtransversemomentum.ATLAShassearched
foranexcessinsuchfinalstatesusing1.1fb 1ofdata[15]. duction is very large. SUSY particles may be long-lived,
−
whentheirdecayissuppressedkinematically(splitSUSY,
Theselectionrequirestwophotons,identifiedwith“tight”
R-hadrons,anomaly-mediatedSUSYbreaking,certainparts
criteria,with p > 25GeV,andsignificantmissingtrans-
T
of phase space of gauge-mediatedSUSY breaking)or by
versemomentum.Theresultsareinterpretedinthegeneral
verysmallcouplings(e.g.R-parityviolation).ATLAShas
gauge mediation model (GGM), in terms of limits in the
carried out searches for stable massive particles [17], for
gluino-neutralinomassplane,andassumingtheneutralino
stoppedgluinos[18],forkinkedordisappearingtracks[19]
tobetheNLSP.TheresultsareshowninFigure8.Theas-
andforsecondaryverticesofdecayingmassiveparticles[20].
sumptionismadethatphotonsareproducedpromptly,i.e.
Furthermore,there is a dedicatedsearch for third genera-
cτoftheNLSPisassumedtobelessthan0.1mm.Inthis
tion sneutrinos decaying to an electron-muon pair in R-
model,agluinomassbelow805GeVisexcludedforbino
parity violation scenarios [21]. It is also noteworthy that
massesabove50GeV.
ATLAShassearchedforascalarpartnerofthegluon[22].
Thediphotonplusmissingtransversemomentumanal-
Kinkedordisappearingtracksareapossiblesignature
ysis is also interpreted in the minimal gauge mediation
ofhigh-p massiveparticlesdecayinginthedetectorvol-
model(GMSB),fortheSPS8parametersM =2Λ,N = T
mes 5
ume to an almost degenerate daughter particle, such as
1,tanβ=15andµ>0.TheATLASresultsimplyalower
limitonΛfortheSPS8parametersof145TeVat95%CL. χ˜±1 χ˜01π±inanomaly-mediatedSUSYbreaking(AMSB)
Multileptonanalyses[4,16]aresensitivetoproduction mod→els, where χ˜±1 and χ˜01 are almost degenerate, and the
ofcharginosand/orneutralinosotherthantheLSP,decay- resultingpiontrackhaslow p andiseasilymissedinthe
T
ing leptonically to the LSP. These analyses comprise the reconstruction. ATLAS has searched for such signatures
goldensearch modesat the Tevatron,butare also rapidly in 1.0 fb 1 of data [19], demandinga track p of at least
− T
gaining relevance at the LHC. ATLAS searches for ex- 10 GeV, good reconstruction quality in the silicon track-
cessesinfinalstateswiththreeormoreleptonsonthe2011 ingdetectorsandintheinnerlayersofthetransitionradi-
dataareinprogress.ATLAShaspublishedresultsofvar- ation tracker (TRT), but no, or only few hits in the outer
ious analyses searching for dilepton events plus missing layerof theTRT. Backgroundsarise fromtracksinteract-
momentum, in 1.0 fb 1 of data [4]. Three signal regions ing with the TRT material(dominant),or frommisrecon-
−
aredefinedforopposite-chargeleptons,andtwosignalre- structed low-p tracks. Figure 10 (top)shows probability
T
gions are defined for same-charge leptons, with varying density functions (pdfs) in p for signal and background
T
HadronColliderPhysicsSymposium2011
bability density1100-1-21 ATLAS Prelims=i7nTaerVy SHBiaagddn ratorlan: c LtkrLa 0bc1ak,c bτk(agχ∼cr±1ok) ug=nr o1dunnsd x mass [GeV]102 ×111..460-3
Pro10-3 Verte 1.2
1
10-4 Signal region
10 0.8
10-5 ATLAS
∫ 0.6
Ldt = 33 pb-1
10-6
102 103 0.4
track pT [GeV] 1 Data 2010
0.2
V102 Signal MC
Ge Data 0
1 2 3 4 5 6 78910 20 30 40
s / 10 Fit results Number of tracks in vertex
k
c
a
Tr
1
ATLAS Preliminary Fig.11.Vertexmassandnumberoftracksinthesecondaryver-
s=7TeV, ∫Ldt = 1.02 fb-1 tex,forverticesselectedbytheanalysissearchingforhighmass
10-1 secondaryvertices.
10-2
in triggering,andindealingwithhighpile-upconditions.
Inthelongerterm,increasingtheLHCbeamenergyto>6
10-3
10 20 50 100 200 500 1000 TeVwillagainenablethecrossingofkinematicalbarriers
track p [GeV] andopenthewayformulti-TeVSUSYsearches.
T
Fig. 10. Top: Probability density functions for signal (AMSB
model) and expected background distributions of track p for
T References
trackssatisfyingthekinked-trackselection.Bottom:Distribution
oftrack p for185tracksindatasatisfyingthekinked-trackse-
T 1. See the reviews of S. P. Martin, hep-ph/9709356 and
lection,andtheresultofthepdffit.Thefitisconsistentwiththe
H. P. Nilles, Phys. Rept. 110 (1984) 1, and references
background-onlyhypothesis.
therein.
2. ATLASCollaboration,arXiv:1109.6572(2011)
tracks;Figure10(bottom)showsthe p distributionofthe 3. ATLASCollaboration,arXiv:1109.6606(2011)
T
185tracksindatasatisfyingtheselectioncriteria,andthe 4. ATLASCollaboration,arXiv:1110.6189(2011)
pdf fit to the data. The data is consistent with the back- 5. ATLASCollaboration,JHEP11(2011)99
groundexpectation,andupperlimitsonthesignalareset. 6. ATLAS Collaboration, ATLAS-CONF-2011-156
ATLAShasalsosearchedforhigh-masssecondaryver- (2011),http://cdsweb.cern.ch/record/1398247/
tices,consistentwiththedecayofmassiveparticles,in33 7. D.Alvesetal.,arXiv:1105.2838(2011)
pb 1ofdatacollectedin2010.Theanalysisisdesignedin 8. ATLAS Collaboration, ATLAS-CONF-2011-155
−
particularforthe decayχ˜0 µ˜µandthe R-parityviolat- (2011),http://cdsweb.cern.ch/record/1398201/
ingdecayµ˜ qq¯ through→anon-zeroλ coupling[20]. 9. R.Barbieri,these(HCP2011)proceedings
→ ′ ′2ij 10. ATLASCollaboration,arXiv:1112.3832(2011)
Backgroundsarise from interactionsin the inner detector
11. G.PoleselloandD.Tovey,JHEP03(2010)030
material,andthefiducialvolumeofthisanalysisexcludes
12. ATLAS Collaboration, ATLAS-CONF-2011-130
regionswithsuchdetectormaterial.Asignalregionisde-
(2011),http://cdsweb.cern.ch/record/1383833/
fined requiringa vertexmass of10 GeV or more,with at
13. ATLAS Collaboration, ATLAS-CONF-2011-098
leastfourtracksinthevertex,asshowninFigure11.The
(2011),http://cdsweb.cern.ch/record/1369212/
dataisconsistentwiththebackgroundhypothesis.
14. ATLASCollaboration,arXiv:1109.4725(2011)
15. ATLASCollaboration,arXiv:1111.4116(2011)
16. ATLAS Collaboration, ATLAS-CONF-2011-039
8 Conclusion and Outlook
(2011),http://cdsweb.cern.ch/record/1338568/
17. ATLASCollaboration,Phys.Lett.B703(2011)428,
The results of ATLAS supersymmetry searches are sum- Phys.Lett.B701(2011)1
marizedinFigure12. 18. ATLASCollaboration,(inpreparation)
AlthoughnosignsofSUSYhavebeenfoundsofar,it 19. ATLASCollaboration,(inpreparation)
isimportanttorealizethatactualtestsof“natural”SUSY 20. ATLASCollaboration,arXiv:1109.2242(2011)
are onlyjustbeginning[23]. Inthisrespect, theLHC run 21. ATLASCollaboration,Eur.Phys.J.C71(2011)1809
of2012,withanexpectedluminosityofmorethan10fb−1, 22. ATLASCollaboration,Eur.Phys.J.C71(2011)1828
possibly at √s = 8 TeV, will be very important. How- 23. G.Polesello,these(HCP2011)proceedings
ever,experimentallytherewillbeconsiderablechallenges
EPJWebofConferences
ATLAS SUSY Searches* - 95% CL Lower Limits (Status: Dec. 2011)
MSUGRA/CMSSM : 0-lep + j’s + ET,miss L=1.0 fb-1 (2011) [arXiv:1109.6572] 950 GeV ~q = ~g mass ATLAS
MSUGRA/CMSSM : 1-lep + j’s + ET,miss L=1.0 fb-1 (2011) [arXiv:1109.6606] 820 GeV ~q = ~g mass Preliminary
MSUGRA/CMSSM : multijets + ET,miss L=1.3 fb-1 (2011) [arXiv:1110.2299] 680 GeV ~g mass (for m(~q) = 2m(~g)) ∫
Simpl. mod. : 0-lep + j’s + ET,miss L=1.0 fb-1 (2011) [arXiv:1109.6572] 1.075 TeV ~q = ~g mass (light χ∼01) Ldt = (0.03 - 2.0) fb-1
Simpl. mod. : 0-lep + j’s + ET,miss L=1.0 fb-1 (2011) [arXiv:1109.6572] 875 GeV ~q mass (m(~g) < 2 TeV, light χ∼01) s = 7 TeV
Simpl. mod. : 0-lep + j’s + ET,miss L=1.0 fb-1 (2011) [arXiv:1109.6572] 700 GeV ~g mass (m(~q) < 2 TeV, light χ∼01)
Simpl. mod. : 0-lep + j’s + ET,miss L=1.0 fb-1 (2011) [ATLAS-CONF-2011-155] 700 GeV ~q mass (m(~g) < 2 TeV, m(χ∼01) < 200 GeV)
Simpl. modS. i(m~g→pl. qmqoχ∼d±). :: 10--lleepp ++ jj’’ss ++ EETT,,mmiissss LL==11..00 ffbb--11 ((22001111)) [[AarTXLiAv:S1-1C0O9.N6F60-260]11-155] 60605 0G GeVe V ~g~g m maassss ( m (m(χ∼(01~q)) < < 2 20 T0e GVe, mV,( ∆χ∼01m) (<χ∼ ±2,0 χ∼00 )G / e∆Vm)(~g, χ∼0) > 1/2)
SUSY SimpSli.m mpoSlS.d imim.m (op~gpdl→l... mm(tχ∼toχ∼o±1dχ01∼d).02. ::(→ ~b101-- →ll3eelpp χ∼b 01χ+∼+)01 bb): --2:jj ee-2ltte ssbp -++ jSe jjtS’’sss ++++ EEEETTTT,,,,mmmmiiiissssssss LLLL====1120....0008 53ff bbffbb--11 --11(( 22((22001001111111)) ))[[ Aa[[PArTXrTLeiLAvlAi:Sm1S-1Ci-1nCO0aO.rN6yN1F]8F-229-020]001 G111-e1-V03 098]]χ∼3±19 0m Gae5Vs40 s G(7b~eli2V g0m h Gate~ gχ∼sV sm 01, (am~gms (m~s(l)χ∼ a (01=ms) 2s1(< (χ∼( m601m)0( (χ∼< b~G±1 )8) e <0+V G6m)0e(0χ∼V 02)G))e)V, lightχ∼ 01)
GMSB : 2-lep OSSF + ET,miss L=1.0 fb-1 (2011) [ATLAS-CONF-2011-156] 810 GeV ~g mass (corresp. to Λ < 35 TeV, tanβ < 35)
GGM + Simpl. model : γγ + ET,miss L=1.1 fb-1 (2011) [arXiv:1111.4116] 805 GeV ~g mass (m(bino) > 50 GeV)
GMSB : stable ∼τ L=37 pb-1 (2010) [1106.4143965 ]GeV ∼τ mass
AMSB : long-lived χ∼±1 L=1.0 fb-1 (2011) [9P2r eGle]V χ∼±1 mass (0.5 < τ(χ∼±1) < 2 ns )
Stable massive particles : R-hadrons L=34 pb-1 (2010) [arXiv:1103.1984] 562 GeV ~g mass
~
Stable massive particles : R-hadrons L=34 pb-1 (2010) [arXiv:1103.1984] 294 GeV b mass
Stable massive particles : R-hadrons L=34 pb-1 (2010) [arXiv:1103.1984] 309 GeV ~t mass
Hypercolour scalar gluons : 4 jets, mij ≈ mkl L=34 pb-1 (2010) [arXiv:1110.2168953 ]GeV sgluon mass (excl: msg < 100 GeV, m sg ≈ 140 ± 3 GeV)
RPV : high-mass eµ L=1.1 fb-1 (2011) [arXiv:1109.3089] 1.32 TeV ν∼τ mass (λ,311=0.10, λ312=0.05)
Bilinear RPV : 1-lep + j’s + ET,miss L=1.0 fb-1 (2011) [arXiv:1109.6606] 760 GeV ~q = ~g mass (cτLSP < 15 mm)
10-1 1 10
Mass scale [TeV]
*Only a selection of the available results leading to mass limits shown
Fig. 12. Summary of limitsset on SUSY particlemasses by ATLAS,resulting from analyses of up to2 fb 1 of pp collision data at
−
√s=7TeV.