Prospects for sparticle reconstruction at new SUSY benchmark points Status report ADR for Massimiliano Chiorboli Universita’ and INFN Catania

Prospects for sparticle Prospects for sparticle reconstruction at new reconstruction at new

SUSY benchmark SUSY benchmark pointspoints

Status reportStatus report

ADR for ADR for

Massimiliano ChiorboliMassimiliano Chiorboli

Universita’ and INFN CataniaUniversita’ and INFN Catania

7/10/2002 Massimiliano Chiorboli LHC/LC – Physics Meeting

Benchmark PointsBenchmark Points

Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/0106204)Proposed Post-LEP Benchmarks for Supersymmetry (hep-ph/0106204)

The goal is to try to reconstruct The goal is to try to reconstruct sparticlessparticles

Last time we showed gluino and Last time we showed gluino and sbottom at point B (isajet, 10 fbsbottom at point B (isajet, 10 fb-1-1, 300 , 300 fbfb-1-1), and point G (pythia, 300 fb), and point G (pythia, 300 fb-1-1))

In mSUGRA scenario, Pythia In mSUGRA scenario, Pythia overestimates the BR of the decay overestimates the BR of the decay chain to be selectedchain to be selected

Only ISAJET results in this talkOnly ISAJET results in this talk


Point BPoint B

95.610 = LSP

173.81±136.2lR

361.62±196.5lL

174.420520qR

339.930540qL

361.140524.0bR

575.9tR496.0bL

392.9tL595.1g

pb 77.57TOTSUSY

0A

)(sign

10tan

100m

250m

0

0

21

bb~

g~ pp

b~02

01

~

(17% bL, 10% bR)

(37 % bL, 25% bR)

(0.04 %) 0

1~~

(16.4%) 0

1~~ (83.2%)

ISAPYTHIA masses and BR’s

We use the isajet 7.58 parameters as input parameters to pythia 6.152We use the isajet 7.58 parameters as input parameters to pythia 6.152

(60%)(38%)

PYTHIAPYTHIA


Sbottom and Gluino decay chainSbottom and Gluino decay chain

p

p

g~

b~

b

b

01

~

02

~ ~

Event final state:

• 2 high pt isolated leptons OS

• 2 high pt b jets

• missing Et

10 fb10 fb-1-1 of SUSY events at point B produced with the of SUSY events at point B produced with the “ISAPYTHIA” generator“ISAPYTHIA” generator

Detector simulation: fast simulation (CMSJET 4.801)Detector simulation: fast simulation (CMSJET 4.801)

2 SFOS isolated leptons, pT>15 GeV, ||<2.4

2 b-jets, pT>20 GeV, ||<2.4

SM bkgSM bkg: tt, Z+jet, W+jet, ZZ, WW, ZW: tt, Z+jet, W+jet, ZZ, WW, ZW

B-tagging performed with the FATSIM package of CMSJET: A jet is a B-tagging performed with the FATSIM package of CMSJET: A jet is a b-jet if it contains at least two tracks with a significance b-jet if it contains at least two tracks with a significance ipip> > bcutbcut


First step: First step: 2200 l l++ll- - 11

00

02

~ 01

~

~p

p

g~

b~

b

b

01

~

02

~ ~

~

2

χ~2~

2~

2

χ~max

M

)M)(MM(MM

01

02

SUSY only

E(ll) > 100 GeV

(GeV) )μM(μ )eM(e -

01

02

~~~

01

02

~~~ll, not only

W

W, 0

SUSY + SM

Z+jet

ttbar



Dilepton edge fitDilepton edge fit

Etmiss > 150 GeV

(GeV) )μM(e -)μM(e - )μM(μ )eM(e --

GeV 2.10 78.93

Mmax

GeV 16.78M

)M)(MM(MM

~

2

χ~2~

2~

2

χ~max01

02

Cut on the ECut on the EmissmissTT to have a clean SUSY sample to have a clean SUSY sample

Subtract OFOS lepton pairs to eliminate combinatorial bkgSubtract OFOS lepton pairs to eliminate combinatorial bkg

Fit in good agreement with the MC valueFit in good agreement with the MC value


Sbottom reconstructionSbottom reconstruction

p

p

g~

b~

b

b

01

~

02

~ ~

p

M

M1p

01

02

~

~

GeV 81 M GeV 65

• assuming M(assuming M(1100) known) known

•Selecting events “in edge”Selecting events “in edge”

• Combining the Combining the 2200 obtained obtained

from the two leptons with the from the two leptons with the most energetic b-jet in the eventmost energetic b-jet in the event

47.6σ

GeV 6.64.994b)χ~M( 02

GeV 0.524)b~

M(

GeV 0.496)b~

M(

R

L

10 fb-1

b-tag: >3

Etmiss > 150 GeV

Eb-jet 1 > 250 GeV

E(ll) > 100 GeV

Generated valuesGenerated values Result of the fitResult of the fit

(GeV) b)~M( 02

SMSM

5.2004.0

010.0

)bb~bb~bb~

g~(BR

)bb~bb~bb~

g~(BR01

02R

01

02L


Gluino reconstructionGluino reconstruction

p

p

g~

b~

b

b

01

~

02

~ ~

b)b~

( angle

Next step: reconstruct gluinoNext step: reconstruct gluinosbottomsbottom

I associate the reconstructed sbottom to I associate the reconstructed sbottom to the b-jet closest in angle to itthe b-jet closest in angle to it

10 fb-1

b-tag: >3

Etmiss > 150 GeV

Eb-jet 1 > 250 GeV

E(ll) > 100 GeV

SMSM

GeV 1.955)g~M( Generated valuesGenerated values

1.05

GeV 11.15.185bb)~M( 02

Result of the fitResult of the fit

We achieve a resolution We achieve a resolution better than 10% (still at better than 10% (still at

CMSJET level!)CMSJET level!)(GeV) bb)~M( 0

2


Squark reconstructionSquark reconstruction

Non-sbottom squarks: s~,c~,d~

,u~

Process (pb) n in 10 fb-1

0.5 5000

1.9 19000

0.5 5000

7.0 70000

1.9 19000

28.3 283000

1.8 18000

14.1 141000

0.4 4000

0.8 5000

0.7 7000

~~

~~

g~~g~g~

q~~g~q~

t~t~

q~q~

b~

q~

b~

b~

g~b~

g~

% 10.9 ss~dd~

LL % 13.3 cc~uu~ LL

% 21.1 ss~dd~

RR

% 22.0 cc~uu~ RR

% 17.2 bb~

1

% 10.3 bb~

2

% 5.2 tt~1

Lq~

30% q~02

60% q~1

Rq~

1% q~02

99% q~01

02

~

01

~~ (16.4%)

01

~~ (22.4%)

The right component is The right component is almost negligiblealmost negligible

I have to select non b-jets: more combinatorialI have to select non b-jets: more combinatorial


Squark-gluino event topologiesSquark-gluino event topologies

01

~

p

p

q~

jet

02

~

~q~

jet

2102

01

~,~,~,~

p

p

q~

jet

01

~02

~

~q~

jet

2102

01

~,~,~,~

jet

g~

p

p

q~

jet

01

~02

~

~q~

jet

2102

01

~,~,~,~

jet

g~

jetg~


Event selectionEvent selection

2 SFOS isolated leptons, pT>15 GeV, ||<2.4

2 jets (not b), pT>20 GeV, ||<2.4

• b-jet veto (I reject events having 1 jet with >3)

2ip

Process n in 10 fb-1 2 lepton b veto 2 non b-jet 2 SFOS lep

5378 1052 1041 36 27

18999 2278 2178 154 78

4767 865 476 258 130

69943 14533 4528 4185 1325

18880 2683 2422 1084 614

283199 40309 19847 17100 7198

18311 4819 1337 904 215

141609 12034 10513 7917 4355

3616 890 364 262 91

5153 2046 547 409 126

7063 2219 606 516 161

~~

~~

g~~g~g~

q~~g~q~

t~t~

q~q~

b~

q~

b~

b~

g~b~

g~g~

g~q~

q~q~

q~~

Main squark Main squark sources:sources:


SM backgroundsSM backgrounds

(pb) N 2 lep b-veto2 non

b-jets2 SFOS

isolate lep

ttbar 621 6.21*106 (10 fb-1) 886809 336001 170182 14900

Z+jet

(pthat > 60 GeV)2870 3.9*106 172894 159479 17205 13138

W+jet

(pthat > 60 GeV)7500 2*106 4517 3869 738 2

QCD

50-100 2.86*107 1.9*106 460 270 78 0

100-200 1.64*106 1.9*106 3366 1658 965 0

200-300 6.67*104 1.9*106 11395 5349 4088 0

300-400 8.59*103 1.9*106 19892 9545 7954 1

400-500 1.83*103 1.9*106 28149 13961 11832 2

>500 8.20*102 1.9*106 39902 20343 17581 0


Dilepton edgeDilepton edge

E(ll) > 100 GeV

Etmiss > 50 GeV Et

miss > 100 GeV Etmiss > 150 GeV

It looks much better than the b-jet case. It looks much better than the b-jet case.

Probably a better understanding of the SM bkg’s is needed Probably a better understanding of the SM bkg’s is needed

Reproduce the same procedure as in the sbottom reconstruction method. Reproduce the same procedure as in the sbottom reconstruction method. Start from the dilepton invariant mass edge.Start from the dilepton invariant mass edge.

SMSM

Wtb production?Wtb production?


Squark reconstructionSquark reconstruction

Etmiss > 50 GeV Et


GeV 08 M GeV 65

(GeV) q)~M( 02 (GeV) q)~M( 0

2 (GeV) q)~M( 02

SMSM

Selecting the most energetic jet to be combined with the leptonsSelecting the most energetic jet to be combined with the leptons

B-quark veto useful but not crucialB-quark veto useful but not crucial

Use minimum energy for cut for jet Use minimum energy for cut for jet


Squark massSquark mass

GeV 3.26σ

GeV 5.32.532q)χ~M( 02

GeV 0.537)c~(M)u~M(

GeV 8.542)s~(M)d~

M(

LL

LL

GeV 08 M GeV 65

10 fb-1

SMSM

(GeV) q)~M( 02

anti b-tag: <2

Etmiss > 150 GeV

Ejet 1 > 200 GeV

b-veto

Generated valuesGenerated values


This assumes the mass of theThis assumes the mass of the

neutralino-1 to be known neutralino-1 to be known


Gluino reconstructionGluino reconstruction

try to reconstruct the gluino in squark try to reconstruct the gluino in squark decay chain with the same method.decay chain with the same method.

associate the jet closest in angle to the associate the jet closest in angle to the reconstructed squarkreconstructed squark

Generator levelGenerator level

cos(cos())

)q~,qg~(angle

Etmiss > 50 GeV Et


(GeV) qq)~M( 02 (GeV) qq)~M( 0

2 (GeV) qq)~M( 02


Gluino combinatorial suppressionGluino combinatorial suppression

g~g~g~q~ q~q~

1 jet1 jet

2 jet2 jet

Un upper cut on the energy of the second jet Un upper cut on the energy of the second jet can suppress jets coming from squarkscan suppress jets coming from squarks

Associate the jet closest in angle to the Associate the jet closest in angle to the reconstructed quarkreconstructed quark

Generator levelGenerator level

qg~qq~qq~

E parton (GeV)E parton (GeV)

E jet (GeV)E jet (GeV) E jet (GeV)E jet (GeV) E jet (GeV)E jet (GeV)

CMSJETCMSJET


Gluino mass peakGluino mass peak

5.78

GeV 13.3595.7qq)~M( 02

GeV 1.955)g~M(

GeV 08 M GeV 65

10 fb-1

SMSM

Ejet 2 < 80 GeV

anti b-tag: <2

Etmiss > 150 GeV

Ejet 1 > 200 GeV

b-veto

Generated valueGenerated value


(GeV) qq)~M( 02

Worse resolution but better Worse resolution but better statistics than the gluino statistics than the gluino from the sbottom chainfrom the sbottom chain


M(gluino)-M(squark)M(gluino)-M(squark)

8. 21 σ

GeV 2. 3 0. 94 q) χ~ M( qq) χ~ M(02

02

GeV 1.58)s~/d~

M(-)g~M(

GeV 3.52)c~/u~M(-)g~M(

LL

LL

GeV 08 M GeV 65

10 fb-1

SMSM

Ejet 2 < 80 GeV

anti b-tag: <2

Etmiss > 150 GeV

Ejet 1 > 200 GeV

b-veto



(GeV) q)~M(-qq)~M( 02

02

The difference of masses is independent from the The difference of masses is independent from the neutralino 1 massneutralino 1 mass


Point B: Sbottom and Gluino 300 fbPoint B: Sbottom and Gluino 300 fb-1-1

46

GeV 3500b)~M( 02

GeV 0.524)b~

M(

GeV 0.496)b~

M(

R

L

44

GeV 3865b)~M( 02

GeV 1.955)g~M(

GeV 08 M GeV 75

b-tag: >3

Etmiss > 200 GeV

Eb-jet 1 > 150 GeV

cos (b1-gluino) > 0.4

cos (b1-sbottom) > 0.2

E(ll) > 100 GeV





300 fb-1

300 fb-1

5.2004.0

010.0

)bb~bb~bb~

g~(BR

)bb~bb~bb~

g~(BR01

02R

01

02L

(GeV) bb)~M( 02

(GeV) b)~M( 02


Squark and Gluino at 300 fbSquark and Gluino at 300 fb-1-1

GeV 40σ

GeV 1531q)χ~M( 02

GeV 0.537)c~(M)u~M(

GeV 8.542)s~(M)d~

M(

LL

LL

85

GeV 3593qq)~M( 02

GeV 1.955)g~M( (GeV) qq)~M( 0

2

(GeV) q)~M( 02





300 fb-1

300 fb-1


Questions of the last meetingQuestions of the last meeting

Influence of pile-up at 300 fb-1?Can bL and bR be distinguished?

Effect of the neutralino 1 massEffect of the calo energy scale (syst.)Precision on •BR

(stat: sbottom ~ 5%, squarks ~ 2%)


Effect of the pile-up on the sbottom and gluino Effect of the pile-up on the sbottom and gluino reconstructionreconstruction

40

GeV 2503b)~M( 02

44

GeV 4875b)~M( 02

40

GeV 4864b)~M( 02

33

GeV 6275b)~M( 02

No pile-up

Pile-up

The background increases and the peaks are shifted on the leftThe background increases and the peaks are shifted on the left

100 fb-1


Separation of the two sbottomsSeparation of the two sbottoms

10k

33

GeV 5526b)~M( 02

GeV 0.524)b~

M(

GeV 0.496)b~

M(

R

L

21k

35

GeV 2492b)~M( 02

Even at high integrated luminosities, it doesn’t seem possible to Even at high integrated luminosities, it doesn’t seem possible to separate the two sbottomsseparate the two sbottoms

I try to perform a double gaussian fit on the peakI try to perform a double gaussian fit on the peak

300 fb-1

5.2004.0

010.0

)bb~bb~bb~

g~(BR

)bb~bb~bb~

g~(BR01

02R

01

02L

Both the mass values and the Both the mass values and the coefficient seem to be in coefficient seem to be in agreement with the MCagreement with the MC


Sparticle reconstructionSparticle reconstruction

p

p

g~

b~

b

b

01

~

02

~ ~

GeV M GeV 65 81

Problem 10 measurement!

Mass to ~15-25%from study of various decays

Gluino

GeV 559.3)g~M( M)χ~M(

GeV 585.1)g~M( true)χ~M()χ~M(max0

1

01

01


Sensitivity to M(Sensitivity to M(11))

) GeV )( 3 343 ( ) ( M ) 03 . 0 62 . 1( ) b~

( M01 ) GeV )( 6 421 ( ) ( M ) 03 . 0 72 . 1( ) g~( M

01

At 300 fbAt 300 fb-1-1 we can perhaps have the M( we can perhaps have the M(11) as input from a LC.) as input from a LC.

To evaluate the effect the error on M(To evaluate the effect the error on M(11) on the sbottom and gluino mass ) on the sbottom and gluino mass

measurements, I reconstruct the peaks changing the M(measurements, I reconstruct the peaks changing the M(11) )

(GeV) bb)~M( 02(GeV) b)~M( 0

2

(GeV) )~M( 01 (GeV) )~M( 0

1

Since we have a statistical error of Since we have a statistical error of 3 GeV at 300 fb3 GeV at 300 fb-1-1, to have an uncertainty on , to have an uncertainty on the gluino and sbottom mass given by the M(the gluino and sbottom mass given by the M(11) uncertainty smaller than this ) uncertainty smaller than this

statistical error, we should know M(statistical error, we should know M(11) with an error less than 3/1.6 = 1.9 GeV) with an error less than 3/1.6 = 1.9 GeV


Point G: dilepton edgePoint G: dilepton edge

ran point G using ISAJET BR’s:ran point G using ISAJET BR’s:

0A

)(sign

20tan

120m

375m

0

0

21

02

~

01

~~ (2.5%)

01

~~ (64%)

E(ll) > 100 GeV

(GeV) )μM(μ )eM(e - (GeV) )μM(μ )eM(e -

01

02

~~~

01

02

~~~ll, not only

W

W, 0

300 fb-1


Point G: dilepton edgePoint G: dilepton edge

Etmiss >1 50 GeV Et


300 fb-1 SMSM


Point G: squark and gluino reconstructionPoint G: squark and gluino reconstruction

Etmiss > 250 GeV

Eb-jet 1 > 250 GeV

GeV 012 M GeV 110

GeV 80σ

GeV 6767q)χ~M( 02

GeV 9.773)c~(M)u~M(

GeV 0.778)s~(M)d~

M(

LL

LL

115

GeV 30678qq)~M( 02

GeV 8.860)g~M(

Etmiss > 250 GeV

Eb-jet 1 > 250 GeV

300 fb-1

Eb-jet 2 < 100 GeV

The squark channel seems more efficient than The squark channel seems more efficient than the sbottom onethe sbottom one


Point I: dilepton chainPoint I: dilepton chain

0A

)(sign

35tan

180m

350m

0

0

21

02

~

01

~~ (0.25%)

01

~~ (98%)

In this point it’s impossible to In this point it’s impossible to reconstruct the decay chainreconstruct the decay chain


300 fb-1


Results: Direct reconstructionResults: Direct reconstruction

@ POINT B Squark, sbottom and gluino reconstruction possible even at low

integrated luminosity (10 fb-1) with Resolution <10% Errors 5-6% if approximate M(

) M(llmax) (this approximation is valid only in a mSUGRA scenario for which

M(20) 2M(

)) Precision on mass 1-2% if M(

would be known

Sbottom (L,R) separation possible? At 300 fb-1 and assuming M(

) measured from a LC, we can have errors of 0.5% (if not limited to a few %). Systematics?

@ POINT G Sbottom and gluino reconstruction possible only at high

luminosity At 300 fb-1 we can reconstruct sbottoms and gluino with

resolution 7%, errors 1-2%, assuming M(1) known from a LC

Documents

Prospects for sparticle reconstruction at new SUSY benchmark points Status report ADR for Massimiliano Chiorboli Universita’ and INFN Catania