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Prospects for SUSY at ATLAS and CMS

Prospects for SUSY at ATLAS and CMS. Dan Tovey University of Sheffield. Introduction. SUSY particularly well-motivated solution to gauge hierarchy problem, unification of couplings etc. etc. (see Weiglein talk).

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Prospects for SUSY at ATLAS and CMS

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  1. Prospects for SUSY at ATLAS and CMS Dan Tovey University of Sheffield 1

  2. Introduction • SUSY particularly well-motivated solution to gauge hierarchy problem, unification of couplings etc. etc. (see Weiglein talk). • Also often provides natural solution to Dark Matter problem of astrophysics/cosmology. • One of main motivations for building LHC and GPDs. • Much work carried out historically by LHC experiments esp: • ATLAS Detector and Physics Performance TDR (http://atlasinfo.cern.ch/Atlas/GROUPS/PHYSICS/TDR/access.html). • CMS SUSY mega-note (J. Phys. G28 (2002) 469). • Will concentrate in this talk on more recent studies and areas where new groups/people could get involved. • DISCLAIMER: Will try to cover both CMS and ATLAS activities where relevant, however in places will focus more on ATLAS (personal bias due to familiarity). • Will not cover non-SUSY exotica (ED, BH production etc.) • PS: Spot a missing tilde and win a prize! 2

  3. Model Framework LHCC mSUGRA Points 3 1 2 5 4 • Minimal Supersymmetric Extension of the Standard Model (MSSM) contains > 105 free parameters, NMSSM etc. has more g difficult to map complete parameter space! • Assume specific well-motivated model framework in which generic signatures can be studied. • Often assume SUSY broken by gravitational interactions g mSUGRA/CMSSM framework : unified masses and couplings at the GUT scale g 5 free parameters • (m0, m1/2, A0, tan(b), sgn(m)). • R-Parity assumed to be conserved. • Exclusive studies use benchmark points in mSUGRA parameter space: • LHCC Points 1-6; • Post-LEP benchmarks (Battaglia et al.); • Snowmass Points and Slopes (SPS); • etc… 3

  4. SUSY Signatures p p ~ c01 ~ ~ ~ q ~ c02 l g q q l l • Q: What do we expect SUSY events @ LHC to look like? • A: Look at typical decay chain: • Strongly interacting sparticles (squarks, gluinos) dominate production. • Heavier than sleptons, gauginos etc. g cascade decays to LSP. • Long decay chains and large mass differences between SUSY states • Many high pT objects observed (leptons, jets, b-jets). • If R-Parity conserved LSP (lightest neutralino in mSUGRA) stable and sparticles pair produced. • Large ETmiss signature (c.f. Wgln). • Closest equivalent SMsignature tgWb. 4

  5. Inclusive Searches • One of first tasks of LHC experiments (SUSY cross-section large). • Is LHC sensitive to all phenomenologically favoured models? • Especially important given current interest in focus-point models with large mass scales. • Use 'golden' Jets + n leptons + ETmiss discovery channel. • Heavy strongly interacting sparticles produced in initial interaction • Cascade decay via jets and leptons • R-Parity conservation gives stable LSP (neutralino) at end of chain • Map statistical discovery reach in mSUGRA m0-m1/2 parameter space. • Sensitivity only weakly dependent on A0, tan(b) and sign(m). • Choose 'reasonable' values g e.g.A0=0, tan(b) = 10, 35, sign(m)=+/-1 • Systematic + statistical discovery reach harder to assess • Focus of current and future work. 5

  6. mSUGRA Reach 5s 5s ATLAS 6

  7. SUSY Mass Scale Jets + ETmiss + 0 leptons ATLAS • First measured SUSY parameter likely to be mass scale: • Defined as weighted mean of masses of initial sparticles. • Calculate distribution of 'effective mass' variable defined as scalar sum of masses of all jets (or four hardest) and ETmiss: Meff=S|pTi| + ETmiss. • Distribution peaked at ~ twice SUSY mass scale for signal events. • Pseudo 'model-independent' measurement. • Typical measurement error (syst+stat) ~10% for mSUGRA models for 10 fb-1. 10 fb-1 10 fb-1 ATLAS 7

  8. Exclusive Studies p p ~ c01 ~ ~ ~ ~ q c02 g lR q q l l • With more data will attempt to measure weak scale SUSY parameters (masses etc.) using exclusive channels. • Different philosophy to TeV Run II (better S/B, longer decay chains) g aim to use model-independent measures. • Two neutral LSPs escape from each event • Impossible to measure mass of each sparticle using one channel alone • Use kinematic end-points to measure combinations of masses. • Old technique used many times before (n mass from b decay spectrum, W (transverse) mass in Wgln). • Difference here is we don't know mass of neutral final state particles. 8

  9. Dilepton Edge Measurements ~ ~ c01 c02 ~ l l l • When kinematically accessible c02 canundergo sequential two-body decay to c01 via a right-slepton (e.g. LHC Point 5). • Results in sharp OS SF dilepton invariant mass edge sensitive to combination of masses of sparticles. • Can perform SM & SUSY background subtraction using OF distribution e+e- + m+m- - e+m- - m+e- • Position of edge measured with precision ~ 0.5% (30 fb-1). ~ ~ e+e- + m+m- - e+m- - m+e- e+e- + m+m- 5 fb-1 FULL SIM Point 5 ATLAS ATLAS 30 fb-1 atlfast Modified Point 5 (tan(b) = 6) Physics TDR Preliminary 9

  10. Measurements With Squarks ~ qL ~ ~ c02 ~ c01 q l l l ~ qL ~ ~ c02 c01 q h lq edge llq edge b b 1% error (100 fb-1) 1% error (100 fb-1) • Dilepton edge starting point for reconstruction of decay chain. • Make invariant mass combinations of leptons and jets. • Gives multiple constraints on combinations of four masses. • Sensitivity to individual sparticle masses. bbq edge llq threshold 1% error (100 fb-1) 2% error (100 fb-1) TDR, Point 5 TDR, Point 5 TDR, Point 5 TDR, Point 5 ATLAS ATLAS ATLAS ATLAS 10

  11. ‘Model-Independent’ Masses Sparticle Expected precision (100 fb-1) qL 3% 02 6% lR 9% 01 12% ~ ~ ~ ~ ~ ~ c01 lR ATLAS ATLAS • Combine measurements from edges from different jet/lepton combinations to obtain ‘model-independent’ mass measurements. Mass (GeV) Mass (GeV) ~ ~ c02 qL ATLAS ATLAS Mass (GeV) Mass (GeV) 11

  12. Sbottom Mass p p ~ c01 ~ ~ ~ ~ b c02 g lR b b l l • Following measurement of squark, slepton and neutralino masses move up decay chain and study alternative chains. • One possibility: require b-tagged jet in addition to dileptons. • Give sensitivity to sbottom mass (but actually two peaks). Post-LEP Point B: m0=100 GeV, m1/2 = 250 GeV, tan(b) = 10, A0=0, m>0 CMS 10 fb-1 12

  13. Gluino Mass 300 fb-1 • Can also move further up the decay chain to gain sensitivity to gluino mass. • Can use either light squark decay or sbottom (as here). • Problem with large error on input c01 mass remains g solve by reconstructing difference of gluino and squark/sbottom masses. • Allows separation of b1 and b2 with 300 fb-1. Post-LEP Point B CMS ~ ~ ~ Post-LEP Point B 300 fb-1 CMS 13

  14. Higgs Signatures ~ • Lightest Higgs particle produced copiously in c02 decays if kinematically allowed. • Prominent peak in bb invariant mass distribution. • Possible discovery channel. m0=500 GeV, m1/2 = 500 GeV, tan(b) = 2, A0=0, m<0 CMS 100 fb-1 CMS 14

  15. RH Squark Mass ~ ~ c01 qR q ~ ~ ~ • Right handed squarks difficult as rarely decay via ‘standard’ c02 chain • Typically BR (qRgc01q) > 99%. • Instead search for events with 2 hard jets and lots of ETmiss. • Reconstruct mass using ‘stransverse mass’ (Allanach et al.): mT22 = min [max{mT2(pTj(1),qTc(1);mc),mT2(pTj(2),qTc(2);mc)}] • Needs c01 mass measurement as input. • Also works for sleptons. ~ qTc(1)+qTc(2)=ETmiss ATLAS ATLAS Preliminary Preliminary 30 fb-1 30 fb-1 30 fb-1 Right squark SPS1a ATLAS SPS1a SPS1a Right squark Left slepton Preliminary Precision ~ 3% 15

  16. Heavy Gaugino Measurements ATLAS Preliminary • Also possible to identify dilepton edges from decays of heavy gauginos. • Requires high stats. • Crucial input to reconstruction of MSSM neutralino mass matrix (independent of SUSY breaking scenario). Preliminary Preliminary Preliminary SPS1a ATLAS ATLAS ATLAS 100 fb-1 100 fb-1 100 fb-1 SPS1a 16

  17. Mass Relation Method • Hot off the press: new idea for reconstructing SUSY masses! • ‘Impossible to measure mass of each sparticle using one channel alone’ (Page 8). • Should have added caveat: Only if done event-by-event! • Remove ambiguities by combining different events analytically g ‘mass relation method’ (Nojiri et al.). • Also allows all events to be used, not just those passing hard cuts (useful if background small, buts stats limited – e.g. high scale SUSY). Preliminary ATLAS ATLAS SPS1a 17

  18. Chargino Mass Measurement ~ c+1 q ~ ~ q c01 ~ g p ~ W ~ c01 ~ c02 p q lR ~ q q g ~ q q q l l • Mass of lightest chargino very difficult to measure as does not participate in standard dilepton SUSY decay chain. • Decay process via n+slepton gives too many extra degrees of freedom - concentrate instead on decay c+1g W c01. • Require dilepton c02 decay chain on other ‘leg’ of event and use kinematics to calculate chargino mass analytically. • Using sideband subtraction technique obtain clear peak at true chargino mass (218 GeV). • ~ 3 s significance for 100 fb-1. PRELIMINARY ~ ~ Modified LHCC Point 5: m0=100 GeV; m1/2=300 GeV; A0=300 GeV; tanß=6 ; μ>0 ~ 100 fb-1 18

  19. Measuring Model Parameters Point m0 m1/2 A0 tan(b) sign(m) LHC Point 5 100 300 300 2 +1 SPS1a 100 250 -100 10 +1 Parameter Expected precision (300 fb-1) m0 2% m1/2 0.6% tan(b)  9% A0 16% • Alternative use for SUSY observables (invariant mass end-points, thresholds etc.). • Here assume mSUGRA/CMSSM model and perform global fit of model parameters to observables • So far mostly private codes but e.g. SFITTER, FITTINO now on the market; • c.f. global EW fits at LEP, ZFITTER, TOPAZ0 etc. 19

  20. SUSY Dark Matter • Can use parameter measurements for many purposes, e.g. estimate LSP Dark Matter properties (e.g. for 300 fb-1, SPS1a) • Wch2 = 0.1921  0.0053 • log10(scp/pb) = -8.17  0.04 Baer et al. hep-ph/0305191 LHC Point 5: >5s error (300 fb-1) SPS1a: >5s error (300 fb-1) scp=10-11 pb Micromegas 1.1 (Belanger et al.) + ISASUGRA 7.69 DarkSUSY 3.14.02 (Gondolo et al.) + ISASUGRA 7.69 scp=10-10 pb Wch2 scp scp=10-9 pb 300 fb-1 300 fb-1 No REWSB LEP 2 ATLAS ATLAS Preliminary Preliminary 20

  21. SUSY Dark Matter 'Focus point' region: significant h component to LSP enhances annihilation to gauge bosons ~ ~ c01 t ~ c01 l ~ t1 ~ ~ t1 g/Z/h lR ~ c01 l Slepton Co-annihilation region: LSP ~ pure Bino. Small slepton-LSP mass difference makes measurements difficult. mSUGRA A0=0, tan(b) = 10, m>0 Ellis et al. hep-ph/0303043 • SUSY (e.g. mSUGRA) parameter space strongly constrained by cosmology (e.g. WMAP satellite) data. Disfavoured by BR (b  s) = (3.2  0.5)  10-4 (CLEO, BELLE) Favoured by g-2 (E821) Assuming  = (26  10)  10 -10 from SUSY ( 2 ) 'Bulk' region: t-channel slepton exchange - LSP mostly Bino. 'Bread and Butter' region for LHC Expts. Also 'rapid annihilation funnel' at Higgs pole at high tan(b) 0.094    h2  0.129 (WMAP) 21

  22. Coannihilation Models p p ~ c01 ~ ~ ~ ~ q c02 g lR q q l l • Small slepton-neutralino mass difference gives soft leptons from decay • Low electron/muon/tau energy thresholds crucial. • At high tan(b) stau decay channel dominates. • Need to be able to ID soft taus (good jet rejection). • Study just started within ATLAS examining signatures of these models. • Study point chosen within coannihilation region : • m0=70 GeV; m1/2=350 GeV; A0=0; tanß=10 ; μ>0 • Same model to be used for ATLAS DC2 SUSY study (see later). 22

  23. Coannihilation Signatures • Chosen model point has very rich phenomenology. • Decays of c02 to both lL and lR kinematically allowed. • Double dilepton invariant mass edge structure; • Edges expected at 57 GeV and 101 GeV • Stau decay channels enhanced • Soft tau signatures; • Edge expected at 79 GeV; • Less clear due to poor tau visible energy resolution. • ETmiss>300 GeV • 2 OSSF leptons PT>10 GeV • >1 jet with PT>150 GeV • OSSF-OSOF subtraction applied 100 fb-1 ATLAS ~ ~ ~ Preliminary • ETmiss>300 GeV • 1 tau PT>40 GeV;1 tau PT<25 GeV • >1 jet with PT>100 GeV • SS tau subtraction 100 fb-1 ATLAS Preliminary 23

  24. Super-LHC CMS • Proposal to increase sqrt(s) to 28 TeV, luminosity to 1035 cm-2 s-1 after initial running (14 TeV, Lmax= 1034 cm-2 s-1). • Significant impact on detector performance, esp. tracking, electronics etc. • Increased luminosity improves discovery reach by ~ 300 GeV. • Increased sqrt(s) (less easy technologically) more useful: 800 GeV improvement. • Needs further study. A0 = 0; tanb=10; m>0 24

  25. ATLAS: DC1 SUSY Challenge Modified LHCC Point 5: m0=100 GeV; m1/2=300 GeV; A0=300 GeV; tanß=6 ; μ>0 ATLAS Preliminary • First attempt at large-scale simulation of SUSY signals in ATLAS (100 000 events: ~5 fb-1) in early 2003. • Tested Geant3 simulation and ATHENA (C++) reconstruction software framework thoroughly. • UK sites contributed 40% of initial 50 000 event sample. SUSY Mass Scale ATLAS ll endpoint No b-tag With b-tag Dijet mT2 distribution ATLAS Preliminary Preliminary llj endpoint ATLAS Preliminary 25

  26. Data Challenge Activities • ATLAS has just embarked on DC2 (main production over summer). • SUSY Working Group goals: • To validate complete ATLAS simulation and reconstruction software chain using physics objects in SUSY events (jets, taus, leptons etc.); • To carry out sample physics analyses for well-motivated SUSY models using fully simulated data. • Models to be studied include: • DC1 point (for validation of Geant4 sim. + new reconstruction tools); • New coannihilation point (rich in signatures). • Activity just started (open call for volunteers + phone meeting so far). • UK interest so far from Cambridge, RHUL and Sheffield. • More volunteers very welcome! (please see me for details) • Similar activity within CMS (DC04, PRS SUSY/BSM WG) – aim to scan parameter space and perform detailed studies with specific models in preparation for Physics TDR (late 2005). Contact Luc Pape <luc.pape@cern.ch> if interested. 26

  27. Supersummary • The LHC will be THE PLACE to search for, and hopefully study, SUSY from 2007 onwards. • SUSY searches will commence on Day 1 of LHC operation. • Big challenge for discovery will be understanding systematics. • Many studies of exclusive channels already performed. • Massive scope for further work! • ATLAS and CMS currently focusing on Data Challenges. • Significant UK involvement already. • Please get involved – this is a great opportunity for the UK to exploit its hardware investment. 27

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