Supersymmetry at ATLAS Dan Tovey University of Sheffield

Supersymmetry at ATLAS Dan Tovey University of Sheffield Dan Tovey 1 Kyoto, January 2005

Supersymmetry • Supersymmetry (SUSY) fundamental continuous symmetry connecting fermions and bosons Qa|F> = |B>, Qa|B> = |F> • {Qa, Qb}=-2 mabpm: generators of SUSY ~ ‘square-root’ of translations – Connection to space-time symmetry • SUSY stabilises Higgs mass against loop corrections (gauge hierarchy/fine-tuning problem) – Leads to Higgs mass 135 Ge. V – Good agreement with LEP constraints from EW global fits • SUSY modifies running of SM gauge couplings ‘just enough’ to give Grand Unification at single scale. Dan Tovey 2 Kyoto, January 2005

SUSY Spectrum • SUSY gives rise to partners of SM states with opposite spin-statistics but otherwise same Quantum Numbers. • Expect SUSY partners to have same masses as SM states – Not observed (despite best efforts!) – SUSY must be a broken symmetry at low energy • Higgs sector also expanded Dan Tovey 3 Kyoto, January 2005

SUSY & Dark Matter • R-Parity Rp = (-1)3 B+2 S+L • Conservation of Rp (motivated e. g. by string models) attractive m 1/2 (Ge. V) – e. g. protects proton from rapid decay via SUSY states Universe Over-Closed • Causes Lightest SUSY Particle (LSP) to be absolutely stable • LSP neutral/weakly interacting to escape astroparticle bounds on anomalous heavy elements. • Naturally provides solution to dark matter problem of astrophysics / cosmology • R-Parity violating models still possible not covered here. Dan Tovey Baer et al. 4 m 0 (Ge. V) Kyoto, January 2005

SUSY @ ATLAS • LHC will be a 14 Te. V proton-proton collider located inside the LEP tunnel at CERN. • Luminosity goals: – 10 fb-1 / year (first 3 years) – 100 fb-1/year (subsequently). • First data in 2007. • Higgs & SUSY main goals. • Much preparatory work carried out historically by ATLAS – Summarised in Detector and Physics Performance TDR (1998/9). • Work continuing to ensure ready to test new ideas in 2007. • Concentrate here on more recent work. Dan Tovey 5 Kyoto, January 2005

Model Framework • 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 m. SUGRA/CMSSM framework : unified masses and couplings at the GUT scale g 5 free parameters LHCC (m 0, m 1/2, A 0, tan(b), sgn(m)). m. SUGRA • R-Parity assumed to be conserved. Points • Exclusive studies use benchmark 3 points in m. SUGRA parameter space: • • LHCC Points 1 -6; Post-LEP benchmarks (Battaglia et al. ); Snowmass Points and Slopes (SPS); etc… Dan Tovey 6 5 1 2 4 Kyoto, January 2005

SUSY Signatures • Q: What do we expect SUSY events @ LHC to look like? • A: Look at typical decay chain: p p q g~ ~ q ~ c 02 q ~ c 01 ~ l l l • 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 p. T objects observed (leptons, jets, b-jets). • If R-Parity conserved LSP (lightest neutralino in m. SUGRA) stable and sparticles pair produced. – Large ETmiss signature (c. f. Wgln). • Closest equivalent SM signature tg. Wb. Dan Tovey 7 Kyoto, January 2005

Inclusive Searches • • Use 'golden' Jets + n leptons + ETmiss discovery channel. Map statistical discovery reach in m. SUGRA m 0 -m 1/2 parameter space. Sensitivity only weakly dependent on A 0, tan(b) and sign(m). Syst. + stat. reach harder to assess: focus of current & future work. 5 5 ATLAS Dan Tovey ATLAS 8 Kyoto, January 2005

SUSY Mass Scale • First measured SUSY parameter likely to be mass scale: Jets + ETmiss + 0 leptons – Defined as weighted mean of masses of initial sparticles. ATLAS • Calculate distribution of 'effective mass' variable defined as scalar sum of masses of all jets (or four hardest) and ETmiss: Meff=S|p. Ti| + ETmiss. • Distribution peaked at ~ twice SUSY mass scale for signal events. • Pseudo 'model-independent' measurement. • Typical measurement error (syst+stat) ~10% for m. SUGRA models for 10 fb-1. Dan Tovey 9 10 fb-1 ATLAS 10 fb-1 Kyoto, January 2005

Exclusive Studies • With more data will attempt to measure weak scale SUSY parameters (masses etc. ) using exclusive channels. • Different philosophy to Te. V Run II (better S/B, longer decay chains) g aim to use model-independent measures. p p ~ q ~g q ~ c 02 q ~ l. R l ~ c 01 l • 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. Dan Tovey 10 Kyoto, January 2005

Dilepton Edge Measurements • When kinematically accessible ~ 02 can undergo sequential two-body decay to ~ 01 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 c~02 l c~01 l e+e- + m+m- e+m- - m+e- e+e- + m+m. Point 5 ATLAS ~ l 30 fb-1 atlfast Physics TDR 5 fb-1 FULL SIM ATLAS Modified Point 5 (tan(b) = 6) e+ e- + m+ m- - e + m- - m+ e- • Position of edge measured with precision ~ 0. 5% (30 fb-1). Dan Tovey 11 Kyoto, January 2005

Measurements With Squarks • • ~ q. L 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. ~ q c 02 l l~ l ~ q. L ~ c 01 llq threshold lq edge 1% error (100 fb-1) ATLAS Dan Tovey ATLAS TDR, Point 5 2% error (100 fb-1) TDR, Point 5 ATLAS 12 ~0 c 1 h b llq edge TDR, Point 5 ~ q c 02 b bbq edge 1% error (100 fb-1) TDR, Point 5 ATLAS Kyoto, January 2005

‘Model-Independent’ Masses • Combine measurements from edges from different jet/lepton combinations to obtain ‘modelindependent’ mass measurements. ~ 0 ATLAS Mass (Ge. V) ~ 0 2 ATLAS LHCC Point 5 ~ l. R 1 Mass (Ge. V) ATLAS Mass (Ge. V) ~ q L ATLAS Mass (Ge. V) Sparticle Expected precision (100 fb-1) ~ q. L 3% ~ 02 6% ~ l. R 9% ~ 01 12% Dan Tovey 13 Kyoto, January 2005

Sbottom/Gluino Mass • 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 (actually two peaks) and gluino mass. ~0 mass • Problem with large error on input 1 remains g reconstruct difference of gluino and sbottom masses. ~ ~ • Allows separation of b 1 and b 2 with 300 fb-1. p p ~g ~ b b Dan Tovey ~ c 02 b ~ l. R l ~ ~0 ) m(g)-0. 99 m( 1 = (500. 0 ± 6. 4) Ge. V 300 fb-1 ATLAS SPS 1 a ~) ~ m(g)-m(b 1 = (103. 3 ± 1. 8) Ge. V ~ ~ m(g)-m(b 2) = (70. 6 ± 2. 6) Ge. V ATLAS 300 fb-1 ~0 c 1 SPS 1 a l 14 Kyoto, January 2005

Stop Mass • Look at edge in tb mass distribution. • Contains contributions from – – – ~ ~ tb ~+ g tt 1 1 ~ ~+ ~ g bb 1 bt 1 SUSY backgrounds mtbmax = (443. 2 ± 7. 4 stat) Ge. V Expected = 459 Ge. V 120 fb-1 ATLAS • Measures weighted mean of end-points • Require m(jj) ~ m(W), m(jjb) ~ m(t) LHCC Pt 5 (tan(b)=10) mtbmax = (510. 6 ± 5. 4 stat) Ge. V Expected = 543 Ge. V 120 fb-1 ATLAS LHCC Pt 5 (tan(b)=10) • Subtract sidebands from m(jj) distribution • Can use similar approach with ~ ~ g tt 1 tt ~0 i – Di-top selection with sideband subtraction • Also use ‘standard’ bbll analyses (previous slide) Dan Tovey 15 Kyoto, January 2005

RH Squark Mass • Right handed squarks difficult as rarely decay via ‘standard’ ~ 02 chain ~ g~ 0 q) > 99%. – Typically BR (q R 1 • Instead search for events with 2 hard jets and lots of ETmiss. • Reconstruct mass using ‘stransverse mass’ (Allanach et al. ): m. T 22 = min (1) T (2) T [max{m. T 2(p. Tj(1), q. T (1); m ), m. T 2(p. Tj(2), q. T (2); m )}] q +q =E ~ 0 • Needs 1 mass measurement as input. • Also works for sleptons. miss T q ~ c 01 ATLAS 30 fb-1 Right squark SPS 1 a ~ q. R ATLAS Right squark 100 fb-1 SPS 1 a Left slepton Precision ~ 3% Dan Tovey 16 Kyoto, January 2005

Heavy Gaugino Measurements • 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). SPS 1 a ATLAS 100 fb-1 Dan Tovey ATLAS 100 fb-1 17 ATLAS 100 fb-1 SPS 1 a Kyoto, January 2005

Mass Relation Method • New idea for reconstructing SUSY masses! • ‘Impossible to measure mass of each sparticle using one channel alone’ (Slide 10). – Should have added caveat: Only if done event-by-event! • Assume in each decay chain 5 inv. mass constraints for 6 unknowns (4 ~0 momenta + gluino mass + sbottom mass). 1 • 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). ATLAS Preliminary Dan Tovey ATLAS SPS 1 a 18 Kyoto, January 2005

Chargino Mass Measurement • 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 ~+ g W ~ 0. instead on decay 1 1 • Require dilepton ~ 02 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 Ge. V). • ~ 3 significance for 100 fb-1. Dan Tovey ~0 1 ~ + 1 W q q q ~ q q~ g p p ~ g ~ q q ~ ~01 l. R ~ 0 2 q l PRELIMINARY Modified LHCC Point 5: m 0=100 Ge. V; m 1/2=300 Ge. V; A 0=300 Ge. V; tanß=6 ; μ>0 100 fb-1 19 Kyoto, January 2005 l

Measuring Model Parameters • Alternative use for SUSY observables (invariant mass end-points, thresholds etc. ). • Here assume m. SUGRA/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, TOPAZ 0 etc. Point LHC Point 5 SPS 1 a Parameter m 0 m 1/2 tan(b) A 0 Dan Tovey m 0 m 1/2 A 0 tan(b) sign(m) 100 300 2 +1 100 250 -100 10 +1 Expected precision (300 fb-1) 2% 0. 6% 9% 16% 20 Kyoto, January 2005

SUSY Dark Matter • Can use parameter measurements for many purposes, e. g. estimate LSP Dark Matter properties (e. g. for 300 fb-1, SPS 1 a) – h 2 = 0. 1921 0. 0053 – log 10( p/pb) = -8. 17 0. 04 Micromegas 1. 1 (Belanger et al. ) + ISASUGRA 7. 69 Dan Tovey h 2 Baer et al. hep-ph/0305191 LHC Point 5: >5 error (300 fb-1) SPS 1 a: >5 error (300 fb-1) p=10 -11 pb Dark. SUSY 3. 14. 02 (Gondolo et al. ) + ISASUGRA 7. 69 p=10 -10 pb p 300 fb-1 ATLAS 21 p=10 -9 pb LEP 2 No REWSB Kyoto, January 2005

SUSY Dark Matter • SUSY (e. g. m. SUGRA) parameter space strongly constrained by cosmology (e. g. WMAP satellite) data. m. SUGRA A 0=0, tan(b) = 10, m>0 'Focus point' region: significant ~ h component to LSP enhances annihilation to gauge bosons 'Bulk' region: tchannel slepton exchange - LSP mostly Bino. 'Bread and Butter' region for LHC Expts. Dan Tovey DC 1/2 Rome Ellis et al. hep-ph/0303043 Disfavoured by BR (b s ) = (3. 2 0. 5) 10 -4 (CLEO, BELLE) ~01 ~0 1 22 ~ l. R l l t~1 t t~1 /Z/h Slepton Coannihilation region: LSP ~ pure Bino. Small slepton-LSP mass difference makes measurements difficult. Also 'rapid annihilation funnel' at Higgs pole at 0. 094 h 2 0. 129 (WMAP) high tan(b), stop co -annihilation region at large A 0 Kyoto, January 2005

Coannihilation Signatures • Small slepton-neutralino mass difference gives soft leptons 100 fb-1 – Low electron/muon/tau energy thresholds crucial. ATLAS • Study point chosen within region: – m 0=70 Ge. V; m 1/2=350 Ge. V; A 0=0; tanß=10 ; μ>0; – Same model used for DC 2 study. • ETmiss>300 Ge. V • 2 OSSF leptons PT>10 Ge. V • >1 jet with PT>150 Ge. V • OSSF-OSOF subtraction applied Preliminary ~ ~ • Decays of ~ 02 to both l. L and l. R kinematically allowed. – Double dilepton invariant mass edge structure; – Edges expected at 57 / 101 Ge. V 100 fb-1 • Stau channels enhanced (tanb) – Soft tau signatures; – Edge expected at 79 Ge. V; – Less clear due to poor tau visible energy resolution. Dan Tovey Preliminary 23 ATLAS • ETmiss>300 Ge. V • 1 tau PT>40 Ge. V; 1 tau PT<25 Ge. V • >1 jet with PT>100 Ge. V • SS tau subtraction Kyoto, January 2005

Focus Point Models • Large m 0 sfermions are heavy • Most useful signatures from heavy neutralino decay • Study point chosen within focus point region : – m 0=3000 Ge. V; m 1/2=215 Ge. V; A 0=0; tanß=10 ; μ>0 ~0 → ~0 ll • Direct three-body decays n 1 ~0 )-m( ~0 ) ~ • Edges give m( 0 2 → ~ 01 ll n 1 ~0 → ~ 01 ll 3 ATLAS Z 0 → ll ATLAS 30 fb-1 Preliminary Dan Tovey 24 Kyoto, January 2005

SUSY Spin Measurement • Q: How do we know that a SUSY signal is really due to SUSY? – Other models (e. g. UED) can mimic SUSY mass spectrum • A: Measure spin of new particles. • One proposal – use ‘standard’ two-body slepton decay chain – charge asymmetry of lq pairs measures spin of ~ 02 – relies on valence quark contribution to pdf of proton (C asymmetry) – shape of dilepton invariant mass spectrum measures slepton spin Spin-0 Measure Angle Point 5 ATLAS Spin-½ 150 fb -1 mlq spin-0=flat Polarise Spin-½, Spin-0 mostly wino Dan Tovey 150 fb -1 ATLAS Straight line distn (phase-space) Spin-½, mostly bino 25 Kyoto, January 2005

DC 1 SUSY Challenge • First attempt at large-scale simulation of SUSY signals in ATLAS (100 000 events: ~5 fb-1) in early 2003. • Tested Geant 3 simulation and ATHENA (C++) reconstruction software framework thoroughly. ll endpoint ATLAS Preliminary No b-tag With b-tag llj endpoint Modified LHCC Point 5: ATLAS Preliminary m 0=100 Ge. V; m 1/2=300 Ge. V; A 0=300 Ge. V; tanß=6 ; μ>0 SUSY Mass Scale Dijet m. T 2 distribution ATLAS Preliminary Dan Tovey 26 Kyoto, January 2005

DC 2 SUSY Challenge • DC 2 testing new G 4 simulation and reconstruction. • Points studied: m+m- endpoint – DC 1 bulk region point (test G 4) – Stau coannihilation point (rich in signatures test reconstruction) ATLAS Preliminary DC 1 Point • Further studies planned in run up to Rome Physics Workshop (Focus Point model etc. ) Work in Progress! m+m- endpoint ll endpoint DC 1 Point ATLAS Coannihilation Point Preliminary ll endpoint Dan Tovey 27 Kyoto, January 2005

Preparations for 1 st Physics • Preparations needed to ensure efficient/reliable searches for/measurements of SUSY particles in timely manner: – – Initial calibrations (energy scales, resolutions, efficiencies etc. ); Minimisation of poorly estimated SM backgrounds; Estimation of remaining SM backgrounds; Development of useful tools. • Different situation to Run II (no previous measurements at same Ös) • Will need convincing bckgrnd. estimate with little data as possible. • Background estimation techniques will change depending on integrated lumi. • Ditto optimum search channels & cuts. • Aim to use combination of – Fast-sim; – Full-sim; – Estimations from data. • Use comparison between different techniques to validate estimates and build confidence in (blind) analysis. • Aim to study with full-sim (DC 2) data Dan Tovey 28 Kyoto, January 2005

Background Estimation • Main backgrounds: – – • Also: – Single top – WW/WZ/ZZ Z + n jets W + n jets ttbar QCD Jets + ETmiss + 0 leptons ATLAS 10 fb-1 • Generic approach : – Select low ETmiss background calibration samples; – Extrapolate into high ETmiss signal region. QCD W+jet Z+jet ttbar ATLAS Dan Tovey • Used by CDF / D 0 • Extrapolation non-trivial. – Must find variables uncorrelated with ETmiss • Several approaches developed. • Most promising: Use Z ( ll) + jets to estimate Z ( nn) / W ( ln) + jets 29 Kyoto, January 2005

Top Background • Estimation using simulation possible (normalised to data ttbar selection) – cross-check with data • Isolate clean sample of top events using mass constraint(s). • Then plot ETmiss distribution (large statistical errors), compare with same technique applied to SUSY events (SPS 1 a benchmark model). • Reconstruct leptonic W momentum from ETmiss vector and W mass constraint (analytical approach – quadratic ambiguity). • Select solution with greatest W p. T. • Select b-jet with greatest p. T. • Plot invariant mass of combination. Dan Tovey 30 ATLAS ttbar Preliminary SUSY ATLAS Preliminary Kyoto, January 2005

Top Background • Select events in peak and examine ETmiss distribution. • Subtract combinatorial background with appropriately weighted (from MC) sideband subtraction. • Good agreement with top background distribution in SUSY selection. ttbar ATLAS Preliminary SUSY ATLAS Preliminary • With this tuning does not select SUSY events (as required) • Promising approach but more work needed (no btag etc. ) Histogram – 1 lepton SUSY selection (no b-tag) Data points – background estimate Dan Tovey 31 Kyoto, January 2005

Supersummary • The LHC will be THE PLACE to search for, and hopefully study, SUSY from 2007 onwards (at least until ILC). • SUSY searches will commence on Day 1 of LHC operation. • Many studies of exclusive channels already performed. • Lots of input from both theorists (new ideas) and experimentalists (new techniques). • Renewed emphasis on use of full simulation tools. • Big challenge for discovery will be understanding systematics. • Big effort ramping up now to understand how to exploit first data in timely fashion – – Calibrations Background rejection Background estimation Tools • Massive scope for further work! Dan Tovey 32 Kyoto, January 2005

BACK-UP SLIDES Dan Tovey 33 Kyoto, January 2005

llq Edge • Dilepton edges provide starting point for other measurements. • Use dilepton signature to tag presence of ~ 02 in event, then work back up decay chain constructing invariant mass distributions of combinations of leptons and jets. q~L e. g. LHC Point 5 q ~0 c 2 l ~0 c 1 l • Hardest jets in each event produced by RH or LH squark decays. • Select smaller of two llq invariant masses from two hardest jets ATLAS 1% error (100 fb-1) Physics TDR Point 5 – Mass must be < edge position. • Edge sensitive to LH squark mass. Dan Tovey 34 Kyoto, January 2005

lq Edge • Complex decay chain at LHC Point 5 gives additional constraints on masses. • Use lepton-jet combinations in addition to lepton-lepton combinations. • Select events with only one dilepton-jet pairing consistent with slepton hypothesis g Require one llq mass above edge and one below (reduces combinatorics). ATLAS Point 5 Physics TDR • Construct distribution of invariant masses of 'slepton' jet with each lepton. • 'Right' edge sensitive to slepton, squark and ~ 0 2 masses ('wrong' edge not visible). 1% error (100 fb-1) Physics TDR Point 5 Dan Tovey ATLAS 35 Kyoto, January 2005

hq edge • If tan(b) not too large can also observe two body decay of ~ 02 to ~0. higgs and 1 • Reconstruct higgs mass (2 b-jets) and combine with hard jet. • Gives additional mass constraint. ~ q. L ATLAS q ~0 c 2 ~ c 01 h b b Point 5 1% error (100 fb-1) Physics TDR Dan Tovey 36 Kyoto, January 2005

llq Threshold • Two body kinematics of sleptonmediated decay chain also provides still further information (Point 5). • Consider case where ~ 01 produced near rest in ~ 02 frame. – – ATLAS Physics TDR Point 5 Dilepton mass near maximal. ~ 0 ). p(ll) determined by p( 2 ATLAS Point 5 Physics TDR 2% error (100 fb-1) Dan Tovey • Distribution of llq invariant masses distribution has maximum and minimum (when quark and dilepton parallel). • llq threshold important as contains new dependence on mass of lightest neutralino. 37 Kyoto, January 2005

Mass Reconstruction • Combine measurements from edges from different jet/lepton combinations. • Gives sensitivity to masses (rather than combinations). Dan Tovey 38 Kyoto, January 2005

High Mass m. SUGRA • ATLAS study of sensitivity to models with high mass scales • E. g. CLIC Point K Potentially observable … but hard! ATLAS 1000 fb -1 • Characteristic double peak in signal Meff distribution (Point K). • Squark and gluino production crosssection reduced due to high mass. • Gaugino production significant Dan Tovey 39 Kyoto, January 2005

AMSB • Examined RPC model with tan(b) = 10, m 3/2=36 Te. V, m 0=500 Ge. V, sign(m) = +1. ~ ~ • +/-1 near degenerate with 01. ~ ~ • Search for +/-1 g p+/- 01 (Dm = 631 Me. V g soft pions). • Also displaced vertex due to phase space (ct=360 microns). • Measure mass difference between chargino and neutralino using m. T 2 variable (from m. SUGRA analysis). Dan Tovey 40 Kyoto, January 2005

GMSB • Kinematic edges also useful for GMSB models when neutral LSP or very long-lived NLSP escapes detector. • Kinematic techniques using invariant masses of combinations of leptons, jets and photons similar. • Interpretation different though. • E. g. LHC Point G 1 a (neutralino NLSP with prompt decay to gravitino) with decay chain: ~0 c 2 l Dan Tovey ~ l ~0 c 1 l 41 g ~ G Kyoto, January 2005

GMSB • Use dilepton edge as before (but different position in chain). • Use also l , ll edges (c. f. lq and llq edges in m. SUGRA). • Get two edges (bonus!) in l as can now see edge from 'wrong' lepton (from 02 decay). Not possible at LHCC Pt 5 due to masses. • Interpretation easier as can assume gravitino massless: Dan Tovey 42 Kyoto, January 2005

R-Parity Violation • • Missing ET for events at SUGRA point 5 with and without R-parity violation RPV removes the classic SUSY missing ET signature • Use modified effective mass variable taking into account p. T of leptons and jets in event Dan Tovey 43 Kyoto, January 2005

R-Parity Violation • Baryon-Parity violating case hardest to identify (no leptons). Phase space sample 8 j +2 l – Worst case: "212 - no heavy-quark jets • Test model studied with decay chain: • Lightest neutralino decays via BPV coupling: • Reconstruct neutralino mass from 3 -jet combinations (but large combinatorics : require > 8 jets!) Dan Tovey 44 Kyoto, January 2005

R-Parity Violation • Use extra information from leptons to decrease background. • Sequential decay of to through and producing Opposite Sign, Same Family (OSSF) leptons Decay via allowed where m( ) > m( ) Test point Dan Tovey 45 Kyoto, January 2005

R-Parity Violation • Perform simultaneous (2 D) fit to 3 jet and 3 jet + 2 lepton combination (measures mass of ~02). No peak in phase space sample Gaussian fit: = 118. 9 3 Ge. V, (116. 7 Ge. V) = 218. 5 3 Ge. V (211. 9 Ge. V) • Jet energy scale uncertainty 3% 3 Ge. V systematic • Can also measure squark and slepton masses. Dan Tovey 46 Kyoto, January 2005

R-Parity Violation • Different ”ijk RPV couplings cause LSP decays to different quarks: • Identifying the dominant ” gives insight into flavour structure of model. • Use vertexing and non-isolated muons to statistically separate c- and b- from light quark jets. • Remaining ambiguity from d s • Dominant coupling could be identified at > 3. 5 Dan Tovey 47 Kyoto, January 2005