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Muons from light meson decays

Muons from light meson decays. S. Spagnolo Univ. del Salento and INFN Lecce for the Muon HLT group TAPM 30 October 2007. Outline. Introduction Samples Procedures to extract Muon Trigger Rates Preliminary check of different procedures for estimating the MU6 rate at EF. Introduction.

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Muons from light meson decays

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  1. Muons from light meson decays S. Spagnolo Univ. del Salento and INFN Lecce for the Muon HLT group TAPM 30 October 2007

  2. Outline • Introduction • Samples • Procedures to extract Muon Trigger Rates • Preliminary check of different procedures for estimating the MU6 rate at EF

  3. Introduction • Dominant contributions to Low pT muon trigger rates • decays in flight of light mesons p±, K±, KL • leptonic decay modes of Charmed hadrons • leptonic decay modes of Bottom hadrons • punch-trough of hadronic shower particles: • shower muons • hadrons • The study of the muon trigger performance over these physics events requires • very large samples of minimum bias events • special samples enhancing the signal to be studied

  4. In order of descreasing cross section below 6 GeV/c p/K  m b   c   shower muons punch-through

  5. Samples • Minimum bias • misal1_csc11.005001.pythia_minbias.digit.RDO • several samples simulated with different caches of 12.0.X • Minimum Bias total cross section • From Pythia output on these jobs: 54.71 mb (non single diffractive) • From A. Moraes et al. stot = 102 (pythia*) 118 (phojet) mb snsd = 65 (pythia*) 73 (phojet) mb • Samples with forced decays • The purpose is study rejection cuts for fake muon on high statistics samples- how much suitable for cross section ( rate evaluation ) ? • Minimum bias with PionDecayer • misal1_mc12_V1.005001.pythia_minbias.digit.RDO.v12000604_tid008665 - generated with 12.0.6.1 simulated with 12.0.6.4 • Single Pions with PionDecayer (see S. Grancagnolo in previous TAPM meetings) * Pythia 6.124 with a tuning for MB at LHC based on comparison with DATA http://indico.cern.ch/conferenceDisplay.py?confId=19298 SN-ATLAS-2006-057

  6. Minumum bias with PionDecayer • Abort the simulation of events without a charged pion or kaon with pT>2GeV/c (low pT cut in order to study feed-through of muons below threshold in the trigger acceptance) • cross section of the sample is 34.55 % of standard MB s • Select randomly one p or K above threshold; • flag it with GenStat=9999 • define the proper time td (center of mass frame) of the decay in order to force the decay vertex in a cylinder of R = 1115 mm and L = 3500mm (ID volume) • events with muons from forced decay have to be re-weighted for the probability of the parent p or K to decay before showering • w = Mean Path before hadr. int. x Mp/k / (pc t) • flagged p/k can have hadr. int. before td + decay channel is free • not necessarily there will be a muon in each event • the rest of the event is not biased • other light mesons can freely decay into muons – weight = 1 for them

  7. Procedures to extract Muon Trigger Rates • Latest result in terms of muon trigger rates prepared by the Muon Trigger Group have been presented at the Mini Workshop on trigger menus; 24-25 Sep 2007 – G. Siragusa http://indico.cern.ch/getFile.py/access?contribId=11&sessionId=1&resId=0&materialId=slides&confId=20373 • How are rates computed (mu6, as an example): • obtain from single muons of pT in the range 2 – 100 GeV/c • efficiency of LVL1 mu6 vs pT • efficiency of LVL2 (muComb) w.r.t. LVL1 accepted events • effciency of EF (MuidCombined) w.r.t. LVL2 accepted events • effective thresholds applied at LVL2 and EF in order to keep 90 % eff. at the nominal threshold • convolve efficiencies with cross sections ds/dpT for the most important processes • rate of mu6 at EF for Luminosity = 1031 cm-2 s-1 ~50 Hz • M.A.Dufour running a trigger menu for 1031 cm-2 s-1 on Minimum Bias sample reports a rate of mu6 at EF = 206 Hz

  8. Procedures to extract Muon Trigger Rates • Room for arrange the discrepancy • cross sections ? • Procedure (efficiency on single muons) ? • how trustable is the trigger decision output

  9. Cross sections for muons from light mesons decays used for muon trigger rates from several years ago |h|<2.7 (*) Oren Y. and Nisati L. |h|<2.4 DPMJET default for rates computation (more conservative)

  10. Comparison of oldp/k predictions with new simulations Cross section for muons with pT >4 GeV/c <2.4 from decays in flight of light mesons Normalization to s Minimum bias = 80 mb OLD Pythia 9.85 mb DPMJET 19.5 mb CSC Minimum bias samples (pythia) – 300k events processed p 5.4±1.2mb k 8.9±1.5 mb Total 14.3 mb T.Buanes 11.5 mb (10 Oct. B-Physics meeting) CSC Minimum bias + Pion Decayer – 110k events processed p 5 ± 1mb (16 std decays + 6.4 forced decays) k 5 ± 1 mb (16 std decays + 5.5 forced) Total 10 mb large statistical error driven by standard decays

  11. Comparison of oldp/k predictions with new simulations Cross section for muons with pT >4 GeV/c <2.4from decays in flight of light mesons Normalization to s Minimum bias = 80 mb CSC Minimum bias + Pion Decayer – 110k events processed try to use only forced decays in order to reduce stat. errors: a) 34.5% (16.2) ev. have mesons with pT > 2GeV/c b) multiplicity of p/k in such events is 2.03 / 1.46 c) from forced decays measure eff. for forced p/K to give muons above threshold p 4.2 ± 0.1mb k 4.2 ± 0.3 mb Total 8.4 mb lower statistical error but some systematic effect to be well understood: errors on numbers in a)-c) ? decay volume too small ? any unpredicted bias ?

  12. First look at Muon Rates in MB events • Muon Rates studies in the HLT community are under way for the finalization of the ATLAS detector paper and will be presented at the TP week • tomorrow muon slice meeting to discuss/understand/finalize procedures and numbers • Meanwhile here we present a quick and preliminary look at EF rates for mu6 in comparison with M.A. Dufour at the mini-workshop on trigger menus • running muon trigger slice in 13.0.30.2 over MB (160K events) output in AANT • looking at trigger decision in AOD produced with 12.0.6 for MB (20k events) and J0-J8 samples

  13. First look at Muon Rates in MB events • OLD studies MU6 @ EF 50 Hz • MB AOD MU6 @ EF 1 event accepted  40 ± 40 Hz • MB AOD 0 events / 20k • J0 AOD 15 “  103 ± 27 • J1 14 8 ± 2 • J2 50 8 ± 1 • J3 124 1 ± 0.1 • J0-J8  120 ± 30 Hz • M.A. Dufour for MU4 showed that J0-J8 / MB = 0.57 • assuming this scaling factor is conserved at MU6 (conservative) total MB rate ~ 208 Hz in agreement with M.A.Dufour • MB AANT MU6 @ EF 160 ± 30 Hz (32 accepted ev.s / 160k) • composition: 1 p, 2 k, 18 c, 7 b, 4 feed-through (or not understood)

  14. Conclusions • Current cross sections for light mesons decaying into muons seems in reasonable agreement with old estimates • care must be used with samples with forced decays • larger rates observed with std approach (trigger decision, event counting) w.r.t. to OLD procedure for muon rate estimate • probably low cross sections for muons from charm and bottom have been assumed until now • more news and details for the TP week

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