Experimental%20Research%20on

1
Experimental Research on

at the CMS
Bo ZHU
School of Physics, Peking University

• Motivation
• Results of MC
• Conclusion

2
as a Test of NRQCD

• Heavy quarkonium for QCD testing
• NRQCD and pQCD for CDF quarkonium puzzle
• Polarization
• sources
• Direct
• Prompt ( ) (40)
• B-Decay

3
Current Status of

• Traditional decay length method to distinguish
  prompt
• Detector resolution limitation
• High background

from B-decay , maybe difficult since
Integral Luminosity 10pb-1

No constrain
5-7 0.07(0.02) 0.02(0.02)
7-10 0.09(0.01) 0.02(0.01)
10-15 0.15(0.01) 0.04(0.01)
gt15 0.23(0.02) 0.06(0.02)
High pt get worse
4
Advantage of

• The channel is cleaner
• With an additional photon
• Small b hadrons decay branch ratio
• CMS experiment
• (CDF )
• ECAL , MUON system
  (CDF )

MUONs
ECAL
5
NRQCD Non-Relativistic QCD

• Quarkonium production
• Generate Quark Pair
• Quark Pair involves into quarkonium
• Non-Relativistic
• Heavy quark moves slowly in heavy quarkonium rest
  frame .
• With CSM and COM

Short Distance Coefficient quark-antiquark pair
created. independent of final product. Can be
computed by pQCD
Long Distance Matrix Element Probability of the
quark pair binding to the quarkonium.
6
Polarization

• polarization
• From fragmenting gluon
• 100 transversally polarized
• from ,

Bernd A. Kniehl etc. PHYSICAL REVIEW D, VOLUME
62, 114027
7
Data Samples

• Data sample
• CSM COM,
• 800K Prompt , 3.7pb-1
• 370K
  , 12.8pb-1

• Prompt branch ratio

Decay Branch ratio Events from
1.3 10.4K
36 224K
20 120K
800K 340K
40 prompt events are from
decay
8
Expecting Yield
trigger rates at a
Luminosity 1032cm-2s-1
Event Sample Rate(Hz)
Prompt ( ) 1.4(0.5)
pp??X (include b hadrons decay ) 1.1
S.QIAN CMS B-physics meeting CERN 28/8/2007
10M events pass trigger
in the first year.
9
in Generator Level

• 38K events normalized to 10pb-1
• Only photon are
  reconstructed,(28)
• ECAL acceptance
• Angle can be used to decrease background

cross section

10
Sources of Background

• Sources of Background
• b hadrons decay
• General QCD, Wjets, Zjets

• Sources of Background
• b hadrons decay
• General QCD, Wjets, Zjets

• b hadrons decay branch ratio

b-hadrons
B0 7.11 lt1 94.310.6
B 8.91.4 lt0.4 61.88.6
B0s - - 508.9
BC - - 204.1
b-baryon - - 4.72.8
Journal of Physics G Review of Particle Physics,
Vol 33 (2006), page 779
11
Signal/Background for

• Use constrain
• mass range 2.9-3.3GeV/c2

• b hadrons to fraction

(GeV/c) Signal events Signal events
(GeV/c) No constrain No constrain
5-7 0.07(0.01) 0.02(0.01) 108949 93862
7-10 0.10(0.01) 0.03(0.01) 176900 161105
10-15 0.15(0.01) 0.04(0.01) 129576 123384
gt15 0.22(0.01) 0.07(0.01) 53432 52151
gt25 0.27(0.01) 0.09(0.01) 6970 6908
gt5 0.13(0.01) 0.04(0.01) 468857 430503
12
Signal/Background for

• Use constrain
• mass range 2.9-3.3GeV/c2
• Number of photons lt3
• mass range 3.3-3.7GeV/c2

• b hadrons to fraction

(GeV/c) Signal events Signal events
(GeV/c) No constrain No constrain
5-7 0.07(0.02) 0.02(0.02) 2545 2135
7-10 0.09(0.01) 0.02(0.01) 6027 5489
10-15 0.15(0.01) 0.04(0.01) 4881 4602
gt15 0.23(0.02) 0.06(0.02) 1675 1638
gt5 0.14 (0.01) 0.04(0.01) 15167 13864
13
in High Range
vs.
gt15GeV/c
gt15GeV/c
No constrain

• b hadrons fraction

No constrain
0.23(0.02) 0.06(0.02)
0.22(0.01) 0.07(0.01)
gt15GeV/c
gt15GeV/c
No constrain
14
Summary

• can be used on CMS to
  test NRQCD
• There will be about 10M event pass CMS
  trigger in the first year
• With the constrain of number of photon and
  , the signal of prompt is about 15 times
  of the number of B-decay background in high pT
  range (pTgt15GeV/c).
• Future work
• Polarization study

15
END
Thank you!
16
backup
17
Fraction 0.21
18
Number of photon In prompt chi_cj event Mean
Number of photon In B to J/Psi event
Number of photon In prompt J/Psi event