Muons from Muons from light meson decayslight meson decays

S. Spagnolo Univ. del Salento and INFN Lecce

for the Muon HLT group

TAPM 30 October 2007

OutlineOutlineOutlineOutline

IntroductionSamplesProcedures to extract Muon Trigger

Rates

Preliminary check of different procedures for estimating the MU6 rate at EF

IntroductionIntroductionIntroductionIntroduction

Dominant contributions to Low pT muon trigger rates decays in flight of light mesons ±, 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

In order of descreasing cross section

below 6 GeV/c

/K b c shower muons punch-through

In order of descreasing cross section

below 6 GeV/c

/K b c shower muons punch-through

SamplesSamplesSamplesSamples 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. tot = 102 (pythia*) 118 (phojet) mb

nsd = 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=19298SN-ATLAS-2006-057SN-ATLAS-2006-057

Minumum bias Minumum bias with PionDecayerwith PionDecayerMinumum bias Minumum bias with PionDecayerwith 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

Select randomly one 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 or K to decay before showering

w = Mean Path before hadr. int. x M/k / (pc

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

Procedures to extract Muon Procedures to extract Muon Trigger RatesTrigger RatesProcedures to extract Muon Procedures to extract Muon Trigger RatesTrigger 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 d/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

Procedures to extract Muon Procedures to extract Muon Trigger RatesTrigger RatesProcedures to extract Muon Procedures to extract Muon Trigger RatesTrigger Rates

Room for arrange the discrepancy cross sections ?Procedure (efficiency on single muons) ?

how trustable is the trigger decision output

Cross sections for muons from light mesons Cross sections for muons from light mesons decays used for muon trigger ratesdecays used for muon trigger rates

Cross sections for muons from light mesons Cross sections for muons from light mesons decays used for muon trigger ratesdecays used for muon trigger rates

PYTHIA (*) DPMJET (*)

ot() (all) ( only) (K only) (all) (± only) (K± only)

3<pT<45 GeV38.4 22.8 15.5 81.2 38.1 33.8

36.7 21.9 14.8 77.8 36.6 32.4

4<pT<45 GeV10.3 5.98 4.3 20.3 9.48 8.6

9.85 5.73 4.1 19.5 9.10 8.2

5<pT<45 GeV3.56 2.04 1.53 6.51 3.04 2.7

3.42 1.96 1.47 6.25 2.92 2.6

6<pT<45 GeV1.48 0.83 0.64 2.59 1.21 1.07

1.42 0.79 0.61 2.49 1.16 1.03

(*) Oren Y. and Nisati L.||<2.7

||<2.4 DPMJET default for rates computation (more conservative)

from several years ago

Comparison of oldComparison of old /k/k predictions predictions with new simulationswith new simulationsComparison of oldComparison of old /k/k predictions predictions with new simulationswith new simulations

Cross section for muons with pT >4 GeV/c <2.4 from decays in flight of light mesons

Normalization to Minimum bias = 80 mb

OLD Pythia 9.85 b DPMJET 19.5 b CSC Minimum bias samples (pythia) – 300k events processed

5.4±1.2 b k 8.9±1.5 b Total 14.3 b T.Buanes 11.5 b (10 Oct. B-Physics meeting)

CSC Minimum bias + Pion Decayer – 110k events processed5 ± 1 b (16 std decays + 6.4 forced decays) k 5 ± 1 b (16 std decays + 5.5 forced)Total 10 b large statistical error driven by standard decays

Comparison of oldComparison of old /k/k predictions predictions with new simulationswith new simulationsComparison of oldComparison of old /k/k predictions predictions with new simulationswith new simulations

Cross section for muons with pT >4 GeV/c <2.4 from decays in flight of light mesons

Normalization to Minimum bias = 80 mb

CSC Minimum bias + Pion Decayer – 110k events processedtry to use only forced decays in order to reduce stat. errors:

a) 34.5% (16.2) ev. have mesons with pT > 2GeV/cb) multiplicity of /k in such events is 2.03 / 1.46c) from forced decays measure eff. for forced /K to give muons above threshold

4.2 ± 0.1 bk 4.2 ± 0.3 b Total 8.4 b

lower statistical error but some systematic effect to be well understood:errors on numbers in a)-c) ? decay volume too small ?any unpredicted bias ?

First look at Muon Rates in MB First look at Muon Rates in MB eventsevents

First look at Muon Rates in MB First look at Muon Rates in MB eventsevents

• 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

First look at Muon Rates in MB First look at Muon Rates in MB eventsevents

First look at Muon Rates in MB First look at Muon Rates in MB eventsevents

• 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 , 2 k, 18 c, 7 b, 4 feed-through (or not

understood)

ConclusionsConclusionsConclusionsConclusions

• 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