Heavy Flavor measurements with the ALICE EMCAL detector

Heavy Flavor measurements with the ALICE EMCAL detector

Mark HeinzYale University

EMCAL Meeting, Nantes, July 16, 2008

Mark Heinz EMCAL Meeting Nantes, July 2008 2

Outline

Heavy flavor physics with EMCAL The Essentials

Simulation Status at CD-2 What needs to be done for PPR 2008. B-tagging algorithms

The Optionals (“exciting future measurements”)

Outlook & Summary


Testing pQCD Current theoretical estimates for bottom and charm

production at LHC still have large uncertainties. Charm x-section measurements disagree at RHIC for STAR

and PHENIX by a significant amount.

Theory Uncertainties: NLO pQCD, pp, s = 14 TeV

CERN/LHCC 2005-014,hep-ph/0601164

Large uncertainty in cross-sections


Medium effects on Heavy quarks

Parton energy loss in the medium Magnitude of Dead-cone effect and

quark mass dependence within a limited kinematical range

Quark vs gluon energy loss in the medium (Color Factors) B-jets constitute a very pure sample

of quark jets.

Distinction between AdS/CFT and pQCD?

WHDG, nucl-th/0512076

The Essentials


Annual Heavy Flavor electrons vs backgrounds More detailed rate-plot for 1 year of Pb+Pb running in

EMCAL acceptance.


Electron/Hadron ratio We will need to identify high-pt (>10 GeV/c) electrons. How large are the

hadron backgrounds? Track-EMCAL cluster matching

Max. track-matching efficiency for electrons in Hijing events with tuned EMCAL cuts is ~90% up to 30 GeV/c

~400


EMCAL PID (electron vs hadron) Using matched cluster track-pairs we determine the

momentum/Energy (p/E) ratio of tracks

Resolution of p/E peak for two differentenergies

ElectronsPions


Background Electron Sources Full Simulation of photons in ALIROOT v4-06 include newer

GEANT model of TOF-Geometry (additional material)

<10% convert before TRD/TOF

Integrated over area of EMCAL

Start of EMCAL: 454cm

PYTHIA+GEANT Simulation of mono-energetic photons


Statistical reach of B-jets By triggering on high-pt electrons tightly correlated with the b-jet (Cone

dR<0.2) we are biasing our sample to high pt B-jets. For 70 GeV/c B-jets we obtain about a factor 5 more statistics using a

electron trigger A sample of several hundred B-jets with momenta up to 80 Gev/c will be

acquired during 1 month Pb-Pb running


B-tag: A method - Displaced Vertex Method

The method pursued here has previously been used by CDF to identify secondary vertices from semi-leptonic decays.

Breakdown of method: Find a high-pt electron trigger particle in

EMCAL Pair with all charged hadrons within a cone

of radius dR. Reconstruct “approximate” (average

between B-D decay) secondary vertex and apply more cuts to reduce backgrounds from other leptonic decays.

Plot Lxy distribution and obtain B-contribution from positive/negative imbalance

D0

B-

e-

K/e

Pe+K

r

PrimVtx

SecVtx

Lxy= r .pe+k / |pe+k|

Lxy

CDF Phys.Rev.D66 (2002))


Charm backgrounds (dominant source) Due to the shorter life-time secondary vertices will naturally

have a narrower Lxy distribution. To further reduce displaced vertices from charm by cutting on

the electron-hadron M_inv. Me+h < M + Me + Mh = MD ~ 1.9 GeV

Beauty (after cut) Charm (after cut)


Signal vs. Backgrounds

Electron pT-cut > 10 GeV/c Min. 6 ITS-hits on both electron/hadron track Inv mass of (elec-kaon) mass > 1.7 GeV Pair DCA < 200 m B-Tag = |Lxy| > 600 m

Backgrounds

Cuts used for analysis


Efficiencies & Rejection

All sources

B-jets

Dalitz

ConversionsCharm

B-jets

B-jets B-jets

More stats needed, higher pT


W backgrounds

pT pT

EMCAL Acceptance EMCAL Acceptance

B-jet electrons W electrons

So far only a qualitative look

~10x higher stats


DVM Comparison: B-jet vs WB-jets W

Standard cuts

Standard cuts +Minv> 1.7 GeV(charm rejection)

Standard cuts +Minv> 1.7 GeV + Max ITS-hits

Blue = Signal = right - left


Displaced Vertex simulation results

After applying DVM cuts the signal efficiency is ~30-40%, whereas the backgrounds are factor ~100 suppressed.

Electrons from all sources (before DVM method)

Electrons from all sources (after DVM method)

What needs to be done ?(short-term until PPR)


PPR 2008

Physics Performance Report (PPR) will be prepared for EMCAL for end of 2008. Effort lead by Rene Bellwied 6 different topical working groups formed

All current studies need to be upgraded with more statistics and current version of AliRoot

Electron-Hadron-ID needs to be checked with results from 2007 Testbeam to ensure stability


Preliminary work matrix (PPR)Task Tools Manpower Statistics

Revisit rates

(higher stats)

PYTHIA + Material ---kinematics info

0.5 person 100k x 15 jet pT bins

Re-check e-ID (track-matching, p/E)

PYTHIA/HIJING + Full simulation

0.5 person Single e, 0 10k x ~10 pT ranges

100k x 15 jet pT bins + 10k HIJING bkg

Electron and E-Jet trigger

(rates/bkg)

PYTHIA/HIJING + AliEMCALTrigger, HLT

Trigger Group?

100k x 15 jet pT bins + 10k HIJING bkg

Electron spectra/RAA

(eB/D corresp., compare to TPC and TPC+TRD)

PYTHIA + Full simulation

1 person 100k x 15 jet pT bins

100k x ~5 pThard bins each of MSEL4 and MSEL5

D/B Spectra/RAA (e+D, J/Psi+K, mis-ID)

PYTHIA + Full simulation

1-2 people 100k x 15 jet pT bins

100k x ~5 pThard bins each of MSEL4 and MSEL5

B-jets (DVM,W,JETAN reco, FF, other tag methods)

PYTHIA/HIJING + Full simulation

2-3 people 100k x ~5 pThard bins each of MSEL4 and MSEL5

50-100k W-boson decays

10k HIJING bkg


Non-photonic Electron R-AA Most importantly compare to measurements in Alice with

TPC and TPC+TRD to identify a kinematic regime where EMCAL is unique. How will the EMCAL triggering help enhance our yields ?

Determine photonic conversion probabilities and develop conversion vertex rejection methods ?

non phot. el.


B-tagging

Start of with jet-finding algorithm A brief overview of some different algorithms for b-

tagging (see studies by CDF,D0,CMS…) Secondary, displaced vertex type algorithm (Karlsruhe) Soft lepton tag (INFN) Track-impact parameter based (INFN PISA)

In the end several tags can always be combined in a linear discriminant (LDA) method.


CMS Secondary Vertex Tracker (Weiser et al.)

CMS Note 2006/14


B-Tagging: Track Impact Parameter Based

More details in CMS-Note (Rizzi et al, INFN Pisa) 2006/19

Tagging Variables

First studies were started in Alice by Bonvini, Antinori et al (PWG3, Sep 2007)

“Exciting new measurements”

My personal selection of QM 08 high-lights High-Pt J/ Electron-Charm correlations


Electron-Charm correlations


(K) invariant mass distribution

w/o electron triggerw/o electron triggerw/ non-photonic electron triggerw/ non-photonic electron trigger

Clear D0 signal w/o background subtraction


Electron – Charm correlations (2)

A. Mischke (HP 2008)


J/ at high-pT

Zebo Tang (STAR) QM08

Investigate heavy quarkonium production mechanism and hadronization

• In p+p collision

• Gluon fusion

• Charm fragmentation

• Feed down

• In heavy ion collision

• Gluon energy loss

• Heavy quark energy loss

• Hot-wind dissociation in QGP


High-pT J/ Dissociation or not?

• Double the pT range to 10GeV/c

• Consistent with no suppression at high pT: RAA(pT>5 GeV/c) = 0.9±0.2•Low pT:

RAA(pT<4 GeV/c) = ~0.5

•Indicates RAA increase from low pT to high pT

• Most models expect a decrease RAA at high pT: AdS/CFT: H. Liu, K. Rajagopal and U.A. Wiedemann, PRL 98, 182301(2007) and hep-ph/0607062

Two Component Approach: X. Zhao and R. Rapp, hep-ph/07122407 private communicationZebo Tang (STAR), QM08


J/Psi – hadron correlations


J/Psi – hadron correlations

Zebo Tang (STAR), QM08


Summary

Baseline studies were performed for US CD-2 document in Dec 2007 Need to be updated and improved

EMCAL Physics Performance Report (PPR) is next deadline Structure & meetings are in place

We need to continue to watch new results from RHIC More studies of other observables need to be started now

with a goal of having simulations beyond the PPR


Backup


Z-Boson decay into electrons

Dielectron decays: Main source of background

are jets from misidentified pions.

An isolation cut is mandatory. A track i is rejected if it is found a track j with pt > 2 GeV/c || 0.1 && || 0.1 rad

Zaida . , HP2008R. Bailhache et al: Proc. QM08,


D0 measurement of weak boson

PRL 1995


Z/W predictions from Tevatron toLHC Probe PDF’s

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Heavy Flavor measurements with the ALICE EMCAL detector

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