Z0/*( l + l - )+jet Made in LANL Paul Constantin, Gerd Kunde, Camelia Mironov Signal Background ...
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Transcript of Z0/*( l + l - )+jet Made in LANL Paul Constantin, Gerd Kunde, Camelia Mironov Signal Background ...
Z0/γ*(l+l-)+jet Made in LANL
Paul Constantin, Gerd Kunde, Camelia Mironov
Signal Background
Miscellaneous
NEXT
Camelia Mironov
Introduction Signal Background Conclusions, applause, flowers etc.
Dilepton Tagged Jetsvia
Angular Correlations
Made in LANL (with P. Constantin & G.J. Kunde)
2
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
3
Azimuthal Correlations: Z0/γ*+jet
__
qg*/0Z
l l
q
h
*/0Z
l l
g
h
__
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
4
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
5
PYTHIA Signal at LHC =5.5TeV
Mass_γ* >12GeV (default)
|η| <3.0
PYTHIA v6.326
s
6
PYTHIA Signal at LHC =5.5TeVs
Luminosity = 0.5 (mbs)-1
Run time = 106 (s) (2 weeks)
~NUMBERS:
Z(pT>50 GeV/c) ~790
7
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
8
PYTHIA Z0 Signal
ΔΦ vs pTdilepton
z vs pTdilepton
z=pThadron/pT
dilepton
9
Heavy quarks and their semi-leptonic decay channelsBackground
__
/ ccbb
__
/ DDBB
| | | | | | | |
| | | |__| | | |__
____ | |_____
xyl
xyl xylxyl BR(D --> lxy) ≈ 6.7%BR(B --> lxy) ≈ 10.2%
10
Signal & Background : Theory
Gale, Srivastava,Awes nucle-th/0212081
11
)(_
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
12
My MNR: ΔΦ(ccbar) Distribution
pT(ccbar)>20GeV/cPt(ccbar)>150GeV/c
ccbar: independent trend in ΔΦ with increasing the momentum
13
My MNR: ΔΦ(bbbar) Distribution
)(_
bb
pT(bbbar)>20GeV/c pT(bbbar)>150GeV/c
bbbar: change in ΔΦ when increasing the momentum cut
14
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
15
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
16
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 …
17
The End
18
19
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