Susy+Exotics

1. Susy+Exotics T. Lari INFN Milano Grazie a G. Ciapetti (Roma1), C. Gatti (Frascati), G. Polesello (Pavia), C. Troncon (Milano) per il loro aiuto nel preparare le trasparenze. SUSY+exotics

2. Index Activities on Beyond Standard Model physics in Italy: • SupersimmetryMilano, Pavia, Lecce, Bologna • Z’Frascati, Tor Vergata • Hidden ValleyRoma1, Genova For each of them, I will describe • Motivations • Discovery potential with 2010 data • What need to be understood to fully exploit the discovery potential • Activities, manpower, plans, …. SUSY+exotics

3. Supersymmetry p p ~  ~ ~ ~ q ~  l g q q l l • SUSY particles produced in pairs • Strongly interacting sparticles (squarks, gluinos) expected to dominate production and decay to stable, weakly interacting lightest neutralino. • Event topology: • high pT jets (from squark/gluino decay) • Large ETmiss signature (from LSP) • High pT leptons, b-jets, -jets (depending on model parameters) A typical decay chain: EtMiss +(2-4)jets + no lepton EtMiss +(2-4)jets + 1 lepton EtMiss +(2-4)jets + 2 leptons EtMiss +(2-4)jets + 3 leptons EtMiss +(2-4)(b-)jets EtMiss +(2-4) jets + t EtMiss +(2-4) jets + 2g [models with c01 → G g] Metastable charged/stronlgy interacting particles Most promising search channels ~ ~ Current limits: m(q,g) > 400 GeV s = 10-100 pb for m(q or g)=400-600 GeV ~ ~ SUSY+exotics

4. Strategy for discovery • Count events with a few energetic jets and missing energy, look for excess over SM prediction • Need missing energy tails to be understood and under control • Minimize dependence on MC description of backgrounds: SM predictions using control samples to determine normalization and shape of background distributions • Use multiple techniques to have independent background estimations if possible • Low-mass SUSY has huge cross section, but also more difficult to separate from SM and contaminates control regions (overestimated background, but still ok) A B C D NB = NA*ND/NC SUSY+exotics

5. Discovery channels • All plots for 200 pb-1 and 10 TeV 0 lep S ~ 1000 B ~ 100 1 lep S ~ 400 B ~ 20 2 lep S ~ 60 B ~ 8 SUSY+exotics

6. Discovery reach Assuming 100% uncertainty on background 0-lepton channel: best S/B but QCD is important and may be more difficult to evaluate than W, Z, ttbar 1-lepton channel: very promising and most studied. Good S/B and useful handles: control samples of main backgrounds (W,tt) can be selected with m(l,n)<mW, or explicit top reconstruction. 2-lepton channel: Best S/B but small signal rate. Main background is double leptonic ttbar. Tevatron+LEP Crosses are generated points SUSY searches are also sensitive to New Physics with similar signature. Here, Extra Dimensions with stable, weakly interacting lightest Kaluza-Klein particle SUSY+exotics

7. Italian analyses At the time of CSC, important contribution of Italian institutes (Milano, Pavia, Lecce, Napoli, Bologna) • Editors of two CSC notes and overall CSC chapter • Inclusive 0-lepton search (Bologna) • Inclusive 2-lepton search and first measurements (Milano, Lecce, Napoli, Pavia) • Electron and muon identification criteria and performance in SUSY events After CSC, somewhat less SUSY specific activity • Priority on analyses of ttbar, W, Z with early data (commissioning, early measurements, but also to understand background of SUSY searches) • Some work on data-driven techniques to estimate background to 2-lepton channel • G. Polesello and TL still quite visible in ATLAS SUSY group Plans to carry on the CSC analysis for early data • 0-lepton channel (Bologna) has best S/B but probably will require time to understand all backgrounds • 2-lepton channel the focus of other groups • not much studied by other groups in ATLAS • Relatively high S/B, ttbar by far the most important background SUSY+exotics

8. 2-lepton channel plans • Before collisions – Montecarlo studies • Optimize cuts for 10 TeV and low luminosity, develop a clear strategy for the estimation of background. Some extra effort needed here. • 0 – 10 pb-1 • - Etmiss commissioning, study tails, fake misset cleanup. Starts from the very first collisions. Should take advantage of expertise in Milano (D. Cavalli) • Lepton identification, expecially when several jets are also produced. Starts from the very first W and Z, then W+jets, Z+jets, ttbar. Electrons in Milano, muons in Pavia and Lecce. • 10 – 200 pb-1: actual search • People power available if not overwhelming (at least one post-doc, one PhD, and few seniors spread between Pavia, Lecce and Milano). SUSY+exotics

9. 0-lepton/light stop • Bologna contributed to the 0-lepton channel CSC search • Priority for early data is top physics • One diploma student is studying the qRqR -> qq cc (2j+ETmiss) signal. Will contribute to the 0-lepton channel searches later. More people expected after summer. • Milano and Pavia have historically kicked off search for light (<170 GeV) scalar top pair production in ATLAS • Currently analysis carried on by Geneva, Melbourne. A diploma student from Pavia is also involved. • Needs good understanding of ttbar, some integrated luminosity, b-tagging also very useful. • We may return to this analysis but probably more for 2011 rather than 2010. Experience with ttbar analysis will prove useful. SUSY+exotics

10. Z` • The Z’ leptonic decays are a good candidate for early discovery • Very clean signature (high S/B) • Convincing signal (invariant mass peak) • Fair cross section if mass close to current limits • Relies on the aligment of ID and MS. Misalignments • Degrade efficiency (less signal events) • Affect momentum resolution (peak smeared out) CSC 14 TeV SUSY+exotics

11. A. Salvucci (Tor Vergata) e C. Gatti (Frascati) Effetto di disallineamenti nell’ID e MS sulla selezione di eventi Z' Campione di 1250 pp*Z' con M>0.5 TeV e MZprime =1 TeV (SSM) Selezione: 2 muoni CB o SA pT>20 GeV ||<2.5, carica opposta, M>0.5 TeV, trigger 20 • Abbiamo considerato i seguenti allineamenti del detector: • Allineamento ideale • Rotazioni e spostamenti O(500 m) delle camere del MS (MS500) • ID Curl-Residual (livello atteso dopo allineamento con collisioni) • ID Curl-Large (livello di allineamento già raggiunto coi cosmici) • MS500+Curl-Large(-Residual) Geometria Curl dell’ID: Rotazione lungo l’asse z dei piani dell’ID in maniera proporzionale alla distanza dall’asse in modo da indurre un errore sistematico nella sagitta della tracce di circa 200 (30) m nel caso Large (Residual). Idealmente, una traccia dritta viene ricostruita con un impulso di circa 350 GeV e carica negativa. SUSY+exotics

12. pT/pT carica media + - pT[GeV] Ricostruzione nell’ID con Curl-Large Geometria Curl: SS-q×S pTpT 1/(1-q×S/S) Inversione di carica: S200 m  pT350 GeV Risoluzioni per muoni Stand Alone Geometria ideale vs MS500 Misal: MuonBoy (1/pT) = 0.92 TeV-1 Misal: MuidSA (1/pT) = 0.92 TeV-1 Aligned: MuonBoy (1/pT) = 0.19 TeV-1 Aligned: MuidSA (1/pT) = 0.18 TeV-1 S/S 500m/1 mm  p/p50% per pT=0.5 TeV SUSY+exotics

13. Perdita di efficienza fino a 20% con disallineamenti spettrometro • Aligned • MS500 • Curl-Large • MS500+Curl-Large • Curl-Residual • MS500+Curl-Residual Perdita di efficienza fino a 60 % con disllineamenti Large nell’ID • Aligned • Curl-Large 2<10000 • Curl-Large Impatto dei disallineamenti sulle efficienze di ricostruzione MuidCB Effetto dovuto al matching tra le tracce ID e MS. Stesso effetto nel trigger. Staco molto meno sensibile a disallineamenti ID. Eventi ricostruiti rilasciando il taglio sul 2 della traccia combinata (da 30 a 104). Si recupera tutta la perdita (■). In contatto con A.Poppleton che introdurrà nel calcolo del 2 un termine che tenga conto dell’allineamento tra ID e MS. SUSY+exotics

14. 2 tracks pT-cut charge M-cut trigger MuonBoy 84% 80% 78% 73% 70% Staco 77% 76% 76% 74% 71% MuidSA 83% 77% 75% 71% 69% MuidCB 76% 75% 75% 73% 70% Ideal 2 tracks pT-cut charge M-cut trigger MuonBoy 84% 80% 78% 73% 52% Staco 76% 75% 74% 68% 49% MuidSA 83% 77% 75% 71% 51% MuidCB 35% 33% 33% 30% 28% Curl-L. 2 tracks pT-cut charge M-cut trigger MuonBoy 84% 79% 71% 54% 51% Staco 66% 66% 65% 61% 57% MuidSA 82% 77% 69% 54% 51% MuidCB 66% 64% 64% 59% 57% MS500 Impatto sulla selezione e sulla massa invariante ricostruita ~5 fb-1 SUSY+exotics

15. A look at the future • 0-10 pb-1 • Check resolution from Z lineshape • Verify that the DY spectrum for 100-500 GeV is reproduced by MC (with resolution corrections) • This allows to predict background at high mass (but should still be extremely small) • For 10 pb-1, alignment expected to be much better than the MS500 and Curl-Large considered before • 10-200 pb-1 • Sensible to Z’ up to 2 TeV for most favourable couplings SUSY+exotics

16. Long-lived particles • Predicted in many New Physics models • This is also a good scenario for early discoveries • Cross sections can be high, up to several pb • Striking signatures, difficult for Standard Model processes to mimic them • Main challenge is usually the trigger • Triggers intended for relativistic particles coming from the IP, they often have poor efficiency for exotic new physics processes • Italian institutes involved in developing triggers for neutral states decaying into jets or muons far from the beam pipe • Roma1 for decays in calorimeter or muon spectrometer • Genova for decays in Inner Detector SUSY+exotics

17. Higgs decay to long-lived particles Roma1, Seattle • We use 2 samples to study trigger strategies for this process: • Ideal sample (signal only) • Signal with pileup • pileup for L=1032cm-2s-1 • 4.1 collisions/crossing • 450ns bunch spacing • Parameters: • mh = 140 GeV • mπv = 40 GeV • cτπv = 1500 mm • Events simulated using PYTHIA • Work in collaboration with M. Strassler • Using benchmark model of Higgs decaying to non-interacting pseudo-scalars† (πv) • πv is NEUTRAL under the SM and long-lived †see: M. Strassler & K. Zurek, Phys Lett B 661 (2008) 263-267 S. Chang et al. arXiv:hep-ph/0511250 L. Carpenter et al. arXiv:hep-ph/0607204 SUSY+exotics

18. Current parameters Hidden Valley events are characterized by highly displaced decays leading to jets appearing throughout the volume of ATLAS • Current ATLAS triggers are Interaction Point (IP) centric • Neutral states decaying far from the IP lead to many challenges for the trigger: • Muons from displaced vertices do not have reconstructed tracks in the inner detector and fail the standard ATLAS level-2 muon trigger • Jets from late decays may not have normal energy deposition and could punch through • Depending on where the decay occurs (Inner Detector, Calorimeter, Muon Spectrometer), different approaches are required Need SIGNATURE DRIVEN TRIGGERS SUSY+exotics

19. Decays in the muon system Barrel region (|η|< 1) ATLAS output PYTHIA output End of HCAL 1rst Trigger plane • Average number of L1 muon RoIs contained in a cone of ΔR=0.4 centered around the πv line of flight versus the πv radial decay distance • For πv decays between the Hadronic Calorimeter (4m) and 1rst trigger plane (7m), the event is characterized by greater than 3 L1 muon RoIs in a small (η,ϕ) region SUSY+exotics

20. Decays in the Hcal |η| < 1 • We define a Level 2 trigger using these signatures as: • Log10(EHAD/EEM) > 1 • Isolation wrt Inner Detector tracks • Jets originating inside the ID/ECAL have the “standard” Log10(EHAD/EEM) ~-1 • Jets from πv’s decaying in the HCAL have Log10(EHAD/EEM) ~1.5 • Jets from decays in the HCAL produce very narrow jets • The narrow jet allows us to use a Level-1 τ trigger to select these decays SUSY+exotics

21. Efficiency for Triggering HCAL |η|<1 |η|<1 MS >60% Efficient for decays in the HCAL >70% Efficient for decays in the Muon Spectrometer SUSY+exotics

22. Outlook • Trigger algorithms implemented and included in the trigger menu. EF and off-line selection/analysis in progress. • Spring 2010 with a few pb-1:evaluate trigger background rate and tuning of event selection criteria. • Full 2009/10 sample:assuming a branching fraction of 100% for h→πvπv and a lifetime of 1.5m (20m) we expect ~400 (200) events per 100 pb-1 . Systematics not included! SUSY+exotics

23. Displaced decays to muon pairs(work in progress) • Use a trigger chain based on an isolated muFast muon • New trigger chain in the muon slice: L1_MUxx→ muFast → muIso → EF_MSonly • starts from L1 muon and uses muFast output to seed the muon isolation “muIso” algorithm • EF uses only Muon Spectrometer information • results in a very high absolute efficiency • 89% using L1_MU10 and a 10GeV muFast track to seed muIso (L2: mu10i_MSonly) • 77% using L1_MU20 and a 20GeV muFast track to seed muIso (L2: mu20i_MSonly) (chain already available in ATHENA 15.2.0) • this trigger chain is able to select decays from the IP up to the first muon trigger plane • mu20i_MSonly unprescaled up to high luminosities offline studies needed to define a selective EF algorithm SUSY+exotics

24. Vector boson scattering • Umberto De Sanctis (ATLAS Udine), in collaboration with Marina Cobal, is starting to work on this topic. • The study of this “New Physics” channel comes from the collaboration with the SISSA theoretical group. • A “fast” test of feasibility for “New Physics” model has been developed to improve the collaboration theory-experiment for a quick “reaction” to data in the future: • Theoretical model from SISSA; • Fast study of feasibility with Pythia + PGS detector simulation; • Detailed study within the ATLAS framework: “official generators” + ATLFAST II (signal samples) and “full” simulation (background samples). • In this particular scenario (Phys.Rev.D76:056002,2007 ), neither a fundamental Higgs nor SUSY: EWSB from a new strong interaction at the TeV scale. • The experimental signature is the resonance in the gauge vector bosons invariant mass distribution in high mass region (> 500 GeV). SUSY+exotics

25. VBS analysis Signal: qq → VVqq, one boson (W or Z) decays leptonically, the other hadronically. Backgrounds: W+4jets, Z+4jets, tt Cuts: W/Z leptonic and hadronic candidates, high pt, 2 forward jets, ttbar veto S/B ~ 0.1 after all cuts Discovery possible for 100 fb-1 at 14 TeV 14 TeV WW invariant mass Started to study backgrounds (MC08 samples) and signal (priivate ATLFAST-II) and will report in exotics WG. With 2010 data, one would study the backgrounds kinematics – that is, W+jets, Z+jets, tt SUSY+exotics

26. Conclusions • The italian groups are working on three search for non-SM physics which have the potential to actually find something with 2010 dataset • Supersymmetry • Z’ • Hadronic decays (and m) from long-lived particles • 0-10 pb-1: Efforts will be on understanding detector and backgrounds • Existing expertise on trigger, muons, missing energy will be put to good use in this phase • 10-200 pb-1: if previous step in good shape, explore uncharted territory SUSY+exotics

27. Backup SUSY+exotics

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30. Why don’t we find (m0=305,m1/2=135) in 4jets 1lepton ? Meff cut • (m0=230,m1/2=170) found in 4jets 1lepton : • xsec = 65 pb • after Meff cut : n_data = 31, m_sm = 2.4, corrected ZN = 5.8 • (m0=305,m1/2=135) not found in 4jets 1lepton : • xsec = 457 pb • after Meff cut : n_data = 20, m_sm = 2.4, corrected ZN = 3.7 SUSY+exotics

31. Effect of systematic uncertainties on discovery reach ? 4 jets 0 lepton Medium cuts 4 jets 1 lepton Medium cuts • Systematic uncertainties have very large impact on discovery reach. SUSY+exotics