Z0/γ*(l+l-)+jet Made in LANL

Paul Constantin, Gerd Kunde, Camelia Mironov

Signal Background

Miscellaneous

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Camelia Mironov

Introduction Signal Background Conclusions, applause, flowers etc.

Dilepton Tagged Jetsvia

Angular Correlations

Made in LANL (with P. Constantin & G.J. Kunde)

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p+p : z=pTassociated/pT

trigger Fragmentation function:

A+A: distribution of particles associated with a trigger after medium modification have to disentangle the ‘jet’ component from the global ‘flow’

Azimuthal Correlations: h+h)(

)(ρ

),(ρ)( ]1[

]2[

eventtrigger

eventpairs

trigger

associatedtriggerC

CARTOONflow+jet

jetC

(ΔΦ

)

flow

BKG = B(1+2v2(pTasso)v2(pTtrig)cos(2))

p+p

A+A

Back side

Same side

Trigger Particle

Associated Particles

zdN

Nz pairsaway

trigger

D _1)(

hPt hadorn tagged (triggered) jet

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Azimuthal Correlations: Z0/γ*+jet

__

qg*/0Z

l l

q

h

*/0Z

l l

g

h

__

qq

no flow for dilepton flat global background pT

jet ~ pTZ0/γ* jet energy determined

no ambiguities (π0->2γ, η etc) like in γ+jet

BKG = B(1+2v2(pTasso)v2(pTtrig)cos(2))

The DILEPTON is the tag

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Theory: γ+jet Wang, Huang, Sarcevic PRL 77, 231 (1996)

Wang, Huang PRC 55, 3047 (1997)

Energy loss models (GLV, BDMS etc) connect partonic energy loss to fundamental properties of the medium – gluon density, system size etc

z = pT/pjet

measure D(z) in pp and AA

λa (parton inelastic scattering mean free path)

dEa/dx (parton energy loss)

Arleo et al (hep-ph/0410088), Arleo(hep-ph/0601075): γ-π0 and γ-γ correlations medium modified fragmentation functions

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PYTHIA Signal at LHC =5.5TeV

Mass_γ* >12GeV (default)

|η| <3.0

PYTHIA v6.326

s

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PYTHIA Signal at LHC =5.5TeVs

Luminosity = 0.5 (mbs)-1

Run time = 106 (s) (2 weeks)

~NUMBERS:

Z(pT>50 GeV/c) ~790

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Cross-check for the PYTHIA number …Campbell and Maltoni: cross sections at NLO == MCFM (http://mcfm.fnal.gov)

BR*Lumi*runTime*A^2 ~720 Z0 with pT>50GeV/c

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PYTHIA Z0 Signal

ΔΦ vs pTdilepton

z vs pTdilepton

z=pThadron/pT

dilepton

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Heavy quarks and their semi-leptonic decay channelsBackground

__

/ ccbb

__

/ DDBB

| | | | | | | |

| | | |__| | | |__

____ | |_____

xyl

xyl xylxyl BR(D --> lxy) ≈ 6.7%BR(B --> lxy) ≈ 10.2%

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Signal & Background : Theory

Gale, Srivastava,Awes nucle-th/0212081

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)(_

cc

Understanding background: theory

NLO (HVQMNR) (Mangano, Nason, Ridolfi hep-th/xxxxx)

PYTHIA total

)(_

bb

CERN yellow report on heavy flavor production: hep-ph/0311048

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My MNR: ΔΦ(ccbar) Distribution

pT(ccbar)>20GeV/cPt(ccbar)>150GeV/c

ccbar: independent trend in ΔΦ with increasing the momentum

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My MNR: ΔΦ(bbbar) Distribution

)(_

bb

pT(bbbar)>20GeV/c pT(bbbar)>150GeV/c

bbbar: change in ΔΦ when increasing the momentum cut

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Reduce Background comon sense: DCA cut on displaced lepton track

…understand background first!!

vtx

dca

plepton

pmeson

lepton = e±, μ±

meson = D±, B±

(0,0,0) Profile histogram(value=mean, bars=rms)

Dca(mm)

3<plepton<5 GeV/c5<plepton<7 GeV/c7<plepton<10 GeV/c

10<plepton<13 GeV/c

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If we assume a dca resolution in σrφ~20μm and σz~50μm

totalN

zdcardcaNfrac 150.0||060.0

Statistical error bars

can identify (reject) ~80% of the heavy background

pT dependent trend?

Reduce background: DCA

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Before the end …

Use a weakly interacting probe (Z0/γ*(l+l-)+jet) to tackle the properties of a strong interacting medium

weak is good (this time)

Advantages over ‘traditional’ h-h, γ-h analyses: no flow, no high pT limit etc.

‘Smallish’ rates you can’t have everything (rates, high pT reach and purity) in life

La vita seems to be bella nevertheless …

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The End

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Z0/γ* - jetInitial state radiation

· Σ(pT_incomingPartons)!=0

pTjet !=pT

dilepton

γ*/Z0 γ*/Z0

Final state radiation It will broden the jet

distribution

γ*/Z0 γ*/Z0

pT <100 <200 <300 <400 <500(***) 0.00216774 4.23512e-05 2.35157e-06 3.25855e-07 5.0463e-08