Evaluation of ALICE electromagnetic calorimeterjet event trigger performance for LHC-Run2by simulation
Pure and Applied Sciences
University of Tsukuba
Ritsuya Hosokawa,Tatsuya Chujo,Hiroki Yokoyama
for the ALICE collaboration

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JPS 2015 70th annual meeting1Outline●Detector and L1 Jet algorithm over view
- LHC Run2 and ALICE- ALICE electromagnetic calorimeter- Trigger inputs- L1 Jet trigger patch(EMCALside and DCAL/PHOS side)- L1 Jet processing flow

●p-p trigger performance estimation and Event by event background estimation for Pb-Pb run- Data set- L1 Jet rejection for p-p event- L1 Jet efficiency for p-p event- Background estimation for Pb-Pb event●Summary

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year

LHC Run2 and ALICE●LHC・・・The most largest collider in the world that is
operated by CERN

Run1

2010
2011
2012
2013

Long Shutdown 1(LS1)
For upgrade and tuning ofaccelerator and detectors
●

●Run2

2014
2015

√ s NN = 13~14 TeV (p-p),5.5TeV (Pb-Pb)●ALICEdetector
21/03/2015~2018

LHC-ALICE

The experiment for heavy ioncollision
Reveals the property of QuarkGluon Plasma(QGP)
Expansion of detectors(LS1)(DCAL/PHOS, EMCAL, TRD, TPC-RCU2 upgrade...)JPS 2015 70th annual meeting3

ALICE electromagnetic calorimeter(s)EMCAL(acceptance)Δφ≈107 °A-sideΔη≈1.4

DCAL + PHOS
acceptanceΔφ≈67 °
Δη≈1.4PHOS
acceptanceΔφ≈100 °C-side●EMCAL (ElectroMagnetic CALorimeter)
Sampling type calorimeter which
consists of Pb and scintillators●Δη≈0.24

PHOS (PHOton Spectrometer)

Jet

Homogeneous calorimeter which
consists of PbWO4New!(Run2~)●DCAL (Di-Jet CALorimeter)
Electromagnetic calorimeter which
has same structure as EMCAL
Mainly, measures Di-Jet event and γ-Jet
event as a probe of QGP property

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Trigger inputs●

Minimum component of L0/L1 Trigger processing (FastOR)- from 1 Module signal (EMCAL/DCAL)- from 2x2 Crystals signal (PHOS)

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L1 Jet trigger patch (EMCAL side)●

4x4 FastOR (8x8 Towers)●Subregion●n x n Subregions (n = 2,3,4)(n=4 was used at Run1)●Jet patch

When the Jet patch amplitude
exceeds threshold, L1 is fired

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JPS 2015 70th annual meeting6L1 Jet trigger patch (DCAL/PHOS side)●●In DCAL region, Subregion isdefined as same as EMCALIn PHOS region, 4 different
Subregion size is used
Because of cell size difference
between DCAL and PHOS●

There are about 34 cm
spacial gaps on eta direction
between DCAL and PHOS
This may make trigger
performance worse

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L1 Jet processing flow
●From Run2 heavy ion Run, new online background subtraction method will be used●●

Run1: event by event threshold calculation by using V0 multiplicity
Run2: event by event background subtraction by using background energy that isestimated by opposite side calorimeter

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JPS 2015 70th annual meeting8Data set●

LHC 15b1 (Pythia 13 TeV Min bias with Run2 geometry)For estimate rejection●

Pythia 13TeV p-p event with Jet event
For estimate trigger efficiency●

generated myself

Hijing 5.5TeV Pb-Pb event
For estimate background

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JPS 2015 70th annual meeting9L1 Jet rejection for p-p event●

Jet patch size
4x4 Subregions(32x32 Towers)●~1/1000 rejection@ Threshold = 10GeV

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L1 Jet efficiency for p-p event
efficiency =●Number of Triggered Jets
Number of reconstructed particle level (MC ) Jets inside EMCAL / DCAL acceptance( anti−kt , R=0.2)

Jet patch size
4x4 Subregion(32x32 Tower)●> 90% @ > 50 GeV/c (EMCAL)~100% @ >70 GeV/c (EMCAL)●

80%~90% @ >90 GeV/c (DCAL)

Threshold ≃10 GeV

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Background estimation for Pb-Pb event
These were estimated by using only particle level(MC) track (no detector effect)jetρ jet =median( p T / Area jet )Emedian・・・background energy in BKG patch
BKG
estimated by calorimeter●●

Both of V0 multiplicity and background energy which is estimated bycalorimeter have good relation to Jet rho
Quantitative assessment
In progress

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JPS 2015 70th annual meeting12Summary●I estimated...
- L1 Jet rejection for p-p
For example,about 1/1000 rejection @ threshold 10GeV- L1 Jet efficiency for p-p
Threshold 10GeV...

> 90% @ > 50 GeV/c (EMCAL)~100% @ >70 GeV/c (EMCAL)
80%~90% @ >90 GeV/c (DCAL)- Jet background for Pb-Pb●In future- Quantitative assessment of background estimate accuracy of eachmethod (V0 using method or Calorimeters using method)- estimate rejection and efficiency for Pb-Pb including detector effect- estimate purity
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Backup

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“EMCAL L1 trigger status”, Hiroki Yokoyama(Trigger meeting Tuesday, 17 February 2015)
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●Pythia data
pthardbin_loweredges=( 0 5 11 21 36 57 84 117)
pthardbin_higheredges=( 5 11 21 36 57 84 117 152)
10000 events generated per each pthardbin●Hijing data
0-10% Central
10-50% Central
50-100% Central

3000 events generated per each centrality class

I took configuration from
LHC15b1
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JPS 2015 70th annual meeting16Inclusive Jet Yields
Dijet production in pp@13TeV 2015•‘Flat scenario’–••

MB/RARE = 4 w/ 7 w = 10nb-1 (0.6G) / 5pb-1POWHEG-V2 + CTEQ6M–

NLO + PS (AliRoot)–

Total dijet xsec 7.45mb

Anti-kT R=0.3

estimated by Rachid Guernane

RARE (bullets)
full spacecaloEMCal
DCal+PHOS(No gap)

MB(full lines)

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