Julie Kirk Rutherford Appleton Laboratory ROI based B-triggers Julie Kirk Rutherford Appleton Laboratory Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

RoI guided approach At low luminosity (< 2x1033) introduce a single muon trigger at LVL1 in addition to the di-muon trigger used at high lumi.  tags one b – then try to reconstruct other b (the one of interest) 2 approaches for track reconstruction at LVL2 : Fullscan of ID or RoI-guided (use secondary LVL1 Regions of Interest (RoIs) to guide LVL2 reconstruction). RoI based approach : lower execution time than full-scan: depends on RoI size and mean multiplicity of RoIs lower efficiency for low pT B (slow turn-on threshold) Outline : LVL1 JET and EM RoI multiplicities for bb→X EM RoI triggers (J/ψ→ee and rare radiative decays ((e.g. Bd→K*0γ, Bs→γ):)) Muon RoI triggers (J/ψ→ and rare decays b→(X)) For Jet RoI - comparison of fullscan and RoI guided approach for Bs→Ds((KK)π)π Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

LVL1 RoI multiplicities RoI multiplicity bb→(6)X Limits on cpu and bandwidth for B-triggers => need to be fast, efficient and selective. If retrieve information for smaller region of detector => faster execution times Overall speed depends on RoI size and mean LVL1 RoI multiplicity per event RoI multiplicity required to be about 1-2 to keep resource needs reasonable => determines thresholds chosen. Higher ET threshold → lower rate but also reduce efficiency With required multiplicity efficient for: EM RoI => electron pT>~5GeV Jet RoI => B-hadron pT>~10GeV Jet RoI EM RoI Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

EM RoI Bd J/y (e+e-) Ks(p+p-) J/ψ->e+e- e+ e- TRT EM Calorimeter LVL1: 1 μ (> 6GeV) + ≥1 EM RoI LVL2: confirm LVL1 muon and EM cluster reconstruct tracks in enlarged area around EM RoI (ΔxΔη=1.2x1.2) search for J/ψ, combine opposite sign tracks apply mass cuts Efficiency after LVL2 ~ 68% (both e+/e- pT>5GeV) background ~170 Hz Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

EM RoI (2) Rare radiative decays (e.g. Bd→K*0γ, Bs→γ): Possible with fullscan, investigating possibility of using RoI based trigger Previous “trigger-like” analysis using offline code predicted for 30fb-1 : 15,000 Bd  K*0γ 4,800 Bs γ Rate after EF: 0.6 Hz Bd  K*0 γ 0.5 Hz Bs  γ Need large RoI (half-width ~1) Δφ (γ - daughter) Now repeating analysis using trigger code Δη (γ - daughter) Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

J/ψ→+- LVL2: Efficiency 68-77% (1st  pT>6Gev, 2nd  pT>3GeV) Single muon at LVL1 (22kHz) LVL2 confirm muon (first in muon detector and then combined with ID) => rate ~ 5 kHz Open region around muon and search for J/psi in inner detector. Mass cut (M()>2.8GeV) Extrapolate tracks to muon system. EF : Refit tracks in RoI Vertex reconstruction Efficiency vs. Δη (RoI half-width) 1.1 1 Efficiency 0.9 0.8 0.7 0.6 0.5 0.4 0.3 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 Delta eta J/y  m+ m- efficiency vs. background rate 78 LVL2: Efficiency 68-77% (1st  pT>6Gev, 2nd  pT>3GeV) Background 260-380 Hz 76 74 J/psi Efficiency (%) 72 70 68 Use similar method to improve efficiency for other di-muon channels at low luminosity 66 0.2 0.25 0.3 0.35 0.4 0.45 Background rate, (kHz) Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

Bs→Ds(φπ)π : LVL1 Efficiency pT(Bs) (GeV) Efficiency for B to be within LVL1 RoI LVL1: 1μ (> 6GeV) + ≥1 Jet RoI Jet ET threshold chosen such that RoI multiplicity ~1-2 Efficiency for B (pT>10GeV) to be within RoI is 78% Efficiency pT(Bs) (GeV) Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

Bs→Ds(φπ)π : LVL2 Confirm LVL1 muon (muFast and muComb) True KK(π) combinations Confirm LVL1 muon (muFast and muComb) Reconstruct tracks within a JET RoI (ΔФxΔη=1.5x1.5) Combine pairs of tracks with K+K- mass hypothesis to form φ candidates. Mass cuts: |M(KK) - M(φ)| < 3σ If pass then add third track with π mass hypothesis to form Ds candidates. Apply +/- 3σ mass cuts: |M(KKπ) - M(Ds)| < 3σ Ds →φπ signal Mean = 1.020 GeV σ = 5 MeV bb→µX background M(KK) (GeV) M(KK) (GeV) Ds →φπ signal bb→µX background Mean = 1.968 GeV σ = 18 MeV M(KKπ) (GeV) M(KKπ) (GeV) Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

Bs→Ds(π)π : RoI vs Full Scan For fullscan method: LVL1 muon confirmed at LVL2 reconstruct tracks in whole inner detector Lose less low pT B’s LVL2 efficiencies pT(B)>10 GeV: RoI: 60% Fullscan: 68% Background rate (bb→X) ~ 175Hz (1x1033) Efficiency to select Ds after LVL2 RoI guided Fullscan Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

Timings for track reconstruction LVL2 muon confirmation reduces rate by factor ~4 (21kHz → 5kHz) Time available for track reconstruction x4 (10ms → 40ms) <Time/RoI> = 23ms (<Time/event> = 44 ms) <Time/event> (Fullscan) = 160ms 400 ms 100 ms RoI guided approach ~4 x faster than full scan. Once include EM and muon RoIs as well times may be comparable. Fullscan looks possible for early running or if use a higher muon pT threshold (pT>8GeV => ~2x reduction in rate) Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

Summary Can use single LVL1 muon trigger with reconstruction in secondary RoIs at HLT to increase B-physics programme for low luminosity running Illustrated triggers using Muon, EM and Jet RoIs. Comparison of fullscan vs. RoI guided. Allows flexibility depending on running conditions. Expected efficiencies/rates (including eff~85% for LVL1 muon): channel Efficiency Rate (L=1x1033) Bd J/y (m+m-) Ks ~65% Events with one m pT>6 GeV and other m pT > 3 GeV ~260-380 Hz Bd  J/y (e+e-) Ks ~60% (e+ & e- pT > 5 GeV) ~40% (1st e pT>5 GeV, 2nd e pT>2 GeV) ~170 Hz Bs  Ds p Ds  f (K+K-) p ~50% Events with Bs pT>10GeV and K, K, p pT > 1.5 GeV ~175 Hz Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

Backup slides Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

B→μX: LVL1 JET RoI multiplicities 4x4 Jet RoI Aiming for a multiplicity of 1-2. Implies ET threshold of about 4-5GeV. Varied tower thresholds (EM and hadronic) for individual elements before cluster is formed. Some effect for hadronic case – increased threshold → reduced multiplicity. Investigated different RoI sizes (4x4 and 8x8) Default(EM=500MeV,hadronic=750MeV) EMTowerthresh=750MeV EMTowerthresh=1000MeV HadTowerthresh=1000MeV RoI Multiplicity DC1 and Rome data without pu agree, but won’t necessarily be the case for pile-up data. Need to keep mean multiplicity low to minimise data transfer and cpu usage at LVL2 Aiming for a multiplicity of 1-2 LVL1 Threshold Energy (GeV) Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

Increase hadronic tower threshold (ET>4GeV) reduces efficiency. Bs →Ds(φπ)π:LVL1 efficiencies for B-hadron to be within the RoI (4X4 Jet RoIs) Efficiency ET > 4GeV ET > 5GeV pT(Bs) (GeV) low tower thresh high tower thresh EFFECT OF ET THRESHOLD EFFECT OF HADRONIC TOWER THRESHOLD ET > 4GeV Increase hadronic tower threshold (ET>4GeV) reduces efficiency. BUT reduced ROI multiplicity means can reduce ET threshold to recover similar efficiency. Vary ET threshold For pT(B)>10GeV (offline cut) ET>5GeV => 69% eff. ET>4GeV => 76% eff. Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)

LVL1 efficiencies for B to be in ROI RoI size / tower thresholds ET threshold <nRoI> Efficiency All events pT(B)>10 GeV pT(B)>20 GeV 4x4 jet 4 GeV 5 Gev 1.8 1.1 58% 51% 76% 69% 98% 96% high had TT 3.5 GeV 4.5 GeV 1.5 1.0 50% 68% 97% 8x8 jet 6 GeV 7 GeV 2.0 1.3 55% 49% 72% 66% 5 GeV 59% 53% 78% 71% Studied the effect of varying tower thresholds/RoI sizes → defaults are OK → similar performance achievable with different setups Julie Kirk, RAL ATLAS UK Physics Workshop, Durham (20/9/06)