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 Jets via Angular Correlations Made in LANL (with P. Constantin & G.J. Kunde)

2  p+p : z=p T associated /p T 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 CARTOO N flow+jet jet C(ΔΦ) flow BKG = B(1+2v 2 (p T asso )v 2 (p T trig )cos(2  )) p+p A+A Back side Same side Trigger Particle Associated Particles hPt hadorn tagged (triggered) jet

3 Azimuthal Correlations: Z0/γ*+jet  no flow for dilepton  flat global background  p T jet ~ p T Z0/γ*  jet energy determined  no ambiguities (π 0 ->2γ, η etc) like in γ+jet BKG = B(1+2v 2 (p T asso )v 2 (p T trig )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 = p T /p jet  measure D(z) in pp and AA  λ a (parton inelastic scattering mean free path)  dE a /dx (parton energy loss)  Arleo et al (hep-ph/ ), Arleo(hep-ph/ ): γ-π 0 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

6 PYTHIA Signal at LHC =5.5TeV Luminosity = 0.5 (mbs) -1 Run time = 10 6 (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 ( BR*Lumi*runTime*A^2 ~720 Z0 with pT>50GeV/c

8 PYTHIA Z0 Signal ΔΦ vs p T dilepton z vs p T dilepton z=p T hadron /p T dilepton

9 Heavy quarks and their semi-leptonic decay channels Background | | | | | | | | __| | | |__ ____ | |_____ BR(D --> lxy) ≈ 6.7% BR(B --> lxy) ≈ 10.2%

10 Signal & Background : Theory Gale, Srivastava,Awes nucle-th/

11 Understanding background: theory NLO (HVQMNR) (Mangano, Nason, Ridolfi hep-th/xxxxx) PYTHIA total CERN yellow report on heavy flavor production: hep-ph/

12 My MNR: ΔΦ(ccbar) Distribution pT(ccbar)>20GeV/c Pt(ccbar)>150GeV/c ccbar: independent trend in ΔΦ with increasing the momentum

13 My MNR: ΔΦ(bbbar) Distribution pT(bbbar)>20GeV/cpT(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 p lepton p meson lepton = e ±, μ ± meson = D ±, B ± (0,0,0) Profile histogram (value=mean, bars=rms) Dca(mm) 3<p lepton <5 GeV/c 5<p lepton <7 GeV/c 7<p lepton <10 GeV/c 10<p lepton <13 GeV/c

15  If we assume a dca resolution in σ rφ ~20μm and σ z ~50μm 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

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19 Z0/γ* - jet Initial state radiation · Σ(pT_incomingPartons)!=0  p T jet !=p T dilepton γ*/Z0 Final state radiation  It will broden the jet distribution γ*/Z0 pT<100<200<300<400<500 (***) e e e e-08