Simulation for CMS HI

Dipanwita Dutta 5-6 April,2007, India-CMS Meet, Chandigarh

Simulation for CMS HI

Dipanwita Dutta

Nuclear Physics Division

Bhabha Atomic Research centre

Mumbai, India


Outline

•Cross-section of Z0 (PYTHIA)

•Future Plan: Simulation for Small mass dimuon / Real Photon with CMS

•Simulation and Reconstruction of Z0

with CMKIN+OSCAR+ORCA

Part I

•Muon Reconstruction with CMSSWPart II


Part I

Simulation for Z0


Cross-Section of Z0 (PYTHIA)

0Zqq

0Z)q(qg)q(q

Total

pp(Z

0)

(nb/

GeV

)

Z0 pT (GeV)

For Pb-Pb minbias collision at 5.5 TeV

(Z0+-)

B A2pp(Z0)

68 b


Cross-section and No. of Z0 for Pb+Pb collision s=5.5 TeV for Lint=0.5 nb-1

ProcessesCross-section from PYTHIA pp (Z

0)

PDF CTEQ5M

Cross-section from PYTHIA pp (Z0) PDF

CTEQ5ML

No. of Z0 for central collision (CTEQ5M)

AA=TAA(0)NNpp (Z0)

No. of Z0 for minbias collisionAA=A2 pp (Z

0)

Z0, Z0+jet 48 nb 54 nb 4.3104 1.03106

Z0 16 nb 17.5 nb 1.4104 3.4105

For CMSpT>3.5 GeV

<2.4

Z0, Z0+jet

8.910-1 nb 9.510-1 nb 800 1.9104

mZ-5<M<

mZ+5

6.910-1 nb 7.710-1 nb 621 1.4104

Z0 2.810-1 nb 257 6020


Differential and Integrated Rate of Z0 inPb+Pb collision , s=5.5 TeV for Lint=0.5 nb-1

Barrel+Endcap

│

Barrel only


●

Muon Reconstruction

•Local Muon Reconstruction (L1)

•Stand-Alone Muon Reconstruction (L2)

•Global Muon Reconstruction (L3)

(Combined with Tracker)

•Tag from Muon chambers•Momentum resolution from Silicon Tracker


Simulation of Z0 +- channel

Gen. vs. Rec. Muon from ORCA

pT (GeV)

GenRec


Gen. – Rec. Muon pT,


Reconstruction without backgroundStand Alone Muon Reconstruction


Reconstruction with HI BackgroundStand Alone Muon Reconstruction


Summary : CMKIN-OSCAR-ORCA

• Generation, Simulation and Reconstruction of Z0 performed with HI background using full CMS simulation package CMKIN, OSCAR, ORCA

• Stand Alone Muon Reconstruction show poor mass resolution, Mass width~ 18 GeV at Z0 mass (m/m~0.2)

• Global Muon Reconstruction with Tracker: Mass Resolution with HI background to be studied --- No further Support for ORCA

• Mass Resolution remains unaltered with HI background using Stand Alone Muon Reconstruction


Reconstruction with CMSSW

• CMSSW_1_2_2 downloaded and installed locally at BARC

• Muon Reconstruction using CMSSW: Software available for pp, Reconstruction algorithms for HI under development

• Involvement of BARC for HI Software transportation to CMSSW is required --Olga

• Reconstruction using pp algorithm: Z0 Generation with PYTHIA using CMSSW Generator Interface -- Simulation+ Digitization--Local + Stand Alone Muon Reconstruction


Muon Reconstruction with CMSSW

PT distribution of Generated and Reconstructed muons


Reconstructed-Generated PT Difference


Generated and Reconstructed Invariant Mass

m ~ 14 GeV


Part II

Real Photon/ Small mass Dilepton


Direct Photons at Low pT – RHIC Result

QM 2005: Data consistent with thermal+ NLO pQCD

pQCD uncertain at low pT

Gordon and Vogelsang Phys. Rev. D48, 3136 (1993)

Thermal d’Enterria, Perresounko Eur.Phys.J.C46:451-464,2006

(a) New experimental method for the measurement of

.. / incldirectincl


Future Plan

• Simulation for low mass Dimuon/Photon channel-- Background muons – (DY and open charm and bottom)

• Study the Thermal Dilepton signal (theoretical prediction) and possibility to see the effect of Chemical unsaturation

• Involvement in transportation as well as improvement of reconstruction HI softwares from OSCAR, ORCA to CMSSW

• Global Muon Reconstruction with Tracker information included in CMSSW for

Z0 +-

Simulation for CMS HI

Documents

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