Trigger studies for GMSB with photons

(Internal note for approval)

Shilei ZangBernadette Heyburn, Uriel Nauenberg

University of Colorado, Boulder

TSG Meeting, 19th Mar. 2008

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Outline

• GMSB with photons• Signal and background samples• Efficiency and rate for default triggers• A new method to optimize triggers• Optimization of 3 triggers• Results• Compare rate with other studies• Summary

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G~

01

~

01

~

p p

q

q

q

q ~…

…

jet

jet

jet

jet

G~

~

GMSB with photons

• Gauge Mediated Supersymmetry Breaking models

• NLSP (neutralino) LSP (gravitino) + photon

• Prompt decay (ctau=0)

• high pT photons• large MET due to

gravitinos• multi-jets

Experimental signature

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GMSB parameters

• Λ: scale of the SUSY beraking

• M: messenger mass scale

• tanβ: the ratio of the Higgs vev

• N5: number of messengers

• sign(μ): the sign of Higgsino mass term

• Cgrav : sets NLSP lifetime

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• CSA07 samples of GMSB photons to estimate the signal efficiency.

GEN-SIM: 1_4_X; DIGI-RAW: 1_6_7.

• 100k for each point: GM1b, GM1c, GM1e, GM1f, GM1g

• 1_6_0-PreCSA07 (or 1_6_7-CSA07) samples are used to estimate the background rates, which include:

• Photon jets (all pt bin) (CMSSW_160-PreCSA07)

• QCD jets (all pt bin) (CMSSW_160-PreCSA07)

• Wenu, Zee (CMSSW_167-CSA07)

• Totally processed about15 million events to minimize the error of rate.

GMSB signal samples:

Background samples:

The study have been done under 1_6_0, and optimized for start-up luminosity of 1032 cm-2s-1.

HLTriggerOffiline/Egamma package is used for the study.

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6 paths with thresholds

Single Photon

Relaxed Single Photon

Double Photon

Relaxed Double Photon

EMHighEt(modified-HighEt)

EMVeryHighEt

Et (GeV)

>30 >40 >20 >20 >80 >200

Iso-Ecal (GeV)

<1.5 <1.5 <2.5 <2.5 <5.

Iso-Hcal (Barrel)

<6. <6. <8. <8. H(ΔR<0.15)/Et<5% &&H(0.15<ΔR<0.3)<8.(modified: IHcal<12.)Iso-Hcal

(Endcaps)<4. <4. <6. <6.

Iso-track <1 <1 <3 <3 <4

HLT paths for photons

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QCD Jets

N QCD Jets

N Photon Jets

N Bkg N

0_15 295,613 _470 88,086 0_15 500,000 Wenu 205,707

15_20 1,255,976 _600 55,000 15_20 509,825 Zee 162,219

20_30 2,513,934 _800 21,974 20_30 606,680

30_50 2,416,441 _1000 33,330 30_50 510,094

50_80 2,451,439 _1400 5,299 50_80 169,741

_120 1,161,823 _1800 _120 164,000

_170 499,389 _2200 _170 69,993

_230 428,888 _2600 _300 24,993

_300 172,619 _500 15,554

_380 82,998 _7000 6,666

Number of bkg events processed for rate estimation

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Efficiency and rate for default triggers

RD

RS

D

S

H

VH

SS, RSS, RS, DS, RS, D, RDS, RS, D, RD, Hall

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• Three triggers for GMSB photons:• Optimize the two triggers: EMHighEt (H), and

EMVeryHighEt (VH).• Choose another one from: D, RD, RS, MET, or Jets

Strategy:

How to optimize the triggers?

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Problem: How to optimize the trigger thresholds with figures of Efficiency vs. Rate in an objective way ?

Optimize trigger thresholds

• Usually the cuts are determined by eye to give reasonable values of efficiency and rate. Threshold,

how to set?

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Physics Analysis

• Selection criteria are optimized to maximize statistics (Optimize relative error of BR; Significance; 90% CL limit, etc)

• Selection criteria are optimized to minimize the mass uncertainty in mass measurement (e.g. top mass measurement)

• Artificially reduced the error of physical result!

• Not Really Blind !!

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• N events, the amount of information : log2 N.

• N is number of messengers;

physical results are the meaning of information taken by such N messengers.

• For BR, number of messengers is the meaning of info.;

• For width, mass, … , meaning of info. is taken by the messengers; depends on the kinematics (not just on the number of events).

• Good property: log (xy)= log(x) + log(y).

Information theory

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• Amount of information: log(NS ), log(NB )

• Signal efficiency ε and background efficiency b

• After the cut: log(NS ε), log(NB b)

• Reductions of information: -log(ε), -log(b)

• Ratio of the reductions: log(ε)/ log(b)

• the smaller log(ε)/ log(b), the better

• log(ε)/ log(b) <a ε > ba (0< ε, b, a ≤1).

We can use statistics log(ε)/ log(b) to optimize trigger thresholds!

Good property: Blind Analysis!

log(ε)/ log(b) depends on the amount of information; does not depend on the meaning of information.

log(ε)/ log(b) <a ε > ba .

a=1.0

a=0.7

a=0.5

a=0.3a=0.2a=0.1

a=0.05a=0.02

a=0.01

ε = ba

(1.,1.)

(0.,0.)

Trigger Study

MVA

b

ε ε

ε

b

1-b

K ID

ε

b

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How to deal such a problem in Physics Analysis?

Solution: log(ε)/ log(b) to optimize selections with final ε and b after the kinematics cut.

Our method will give worse physical results, but they are blind analysis and can be trusted.

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log(ε)/ log(b) vs. Cuts (default EMHighEt)

0.0350.129

Min=0.129

Min=0.101 Min=0.00470.0170.102

• Et>80; Iecal<5; Ihcal<12; Itrack<4

• Itrack is better than Iecal and Ihcal.

• Each figure is plotted with other cuts applied.

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log(ε)/ log(b) vs. Cuts (proposed EMHighEt)

• Et>60; Itrack<2

• Itrack is better only when the Itrack cut point <5

0.022Min=0.174

Min=0.190 0.068

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Et>40GeV

Et>40GeV Et>40GeV

Relaxed Single Photon candidates

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• Propose two new triggers:

p-EMHighEt (pH): Et>60GeV, Itrack<2

p-EMVeryHighEt (pVH): Et>120GeV

• Propose to use: pH, pVH, D for our physics.

I. Isolation is useful at low Et region to suppress bkg , but bad in high Et region for our signal.

II. Track isolation (cut position <6) is better than other isolaitons

III.GMSB points with small Lambda parameter (GM1b) have more events with two signal photons at generator level, so the Double trigger is helpful for them.

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Trigger H pH VH pVH H, VH pH, pVH

Rate (Hz) 0.63 2.01 0.13 0.97 0.753 2.888

Efficiency GM1b GM1c GM1e GM1f GM1g Rate (Hz)

RS, H, VH 81.31 85.68 89.58 90.52 91.10 3.510

pH, pVH, D 87.70 91.02 93.27 93.78 93.96 3.139

pH, pVH, RS 88.72 92.28 94.44 94.71 94.72 5.226

2.14 Hz

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efficiency GM1b GM1c GM1e GM1f GM1g Rate (Hz)

pH, pVH, D 87.70 91.02 93.27 93.78 93.96 3.139

pH, pVH, mD 89.77 92.24 93.81 94.14 94.22 3.762

• D: Et>20; Iecal<2.5; Ihcal<8 or 6; Itrack<3 (0.26 Hz)

• mD: Et>20; Itrack<3 (0.90 Hz)0.64 Hz

Further possible improvement

• It’s easy to reach 92% or 93% efficiency with 3.5 Hz, but difficult to reach 95% efficiency within 5.5 Hz!

• 98.6% events have signal photons at generator level; after SusyAnalyzer, only 93.5% events have reconstructed photons.

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Efficiency and Rates for each group of triggers

0: H, VH1: H, VH, RS2: H, VH, RD3: H, VH, D

10: pH, pVH11: pH, pVH, RS12: pH, pVH, RD13: pH, pVH, D

15: pH, pVH, mD

pH, pVH, D

pH, pVH, mD

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Compare the rates with other studies in 13X and 16X

Default Trigger Path

S RS D RD HighEt VeryHighEt

Our Rate (160) (Hz)All bkg

8.96±0.24

2.93±0.09

0.26±0.05

1.90±0.14

0.63±0.01(m-H)

0.13±0.00

13X exercise (Hz) All bkg

8.4±0.7

2.8±0.2

0.6±0.4

1.8±0.5

0.5±0.0

0.1±0.0

16X (Hz)(Matthias Mozer)w/o PhotonJets.

0.8 0.14

16X (Hz)(Aram Avetisyan)w/o PhotonJets;Fewer events.

10.06±4.79

5.82±3.39

0.04±0

6.69±4.61

0.43±0.13

0.07±0.01

Agree well

Agree with error

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• We give the rates of all HLT paths on photons, which are comparable with 13X exercise and other studies in 16X.

• Our rates have small errors.

• We propose to modify EM1HighEt and EM1VeryHighEt tirggers (basically loosen the isolation variables and Et).

• We propose to use 3 triggers for GMSB photons, which can reach ~93% efficiency with 3.2 Hz.

• We find a new method for trigger study, and physics analysis.

Summary

Thank you!

The draft of the note:

http://www-hep.colorado.edu/~slzang/cmsnote_gmsb_trigger_v3.ps