Upsilon nS Production at CMS - PowerPoint PPT Presentation

1 / 1
About This Presentation
Title:

Upsilon nS Production at CMS

Description:

Purdue University: D. Bortoletto, A. Garfinkel, Z. Gecse, M. Jones, N. Leonardo, ... Purdue. Adam Hunt. Princeton. Alex Petrescu. Princeton. Yu Zheng. Purdue ... – PowerPoint PPT presentation

Number of Views:45
Avg rating:3.0/5.0
Slides: 2
Provided by: uscms
Category:

less

Transcript and Presenter's Notes

Title: Upsilon nS Production at CMS


1
Upsilon (nS) Production at CMS
Purdue University D. Bortoletto, A. Garfinkel,
Z. Gecse, M. Jones, N. Leonardo, I. Shipsey, D.
Silvers, Y. Zheng Princeton University N. Adam,
V. Halyo, A. Hunt, A. Petrescu Peking University
S. Guo, S. Qian, Z. Yang, L. Liu
Introduction
Motivations
The narrow resonance of bottomonium, Upsilon
(1S), decaying into a muon pair, certainly plays
an important role in the detector calibration and
alignment.
Alex Petrescu Princeton
Yu Zheng Purdue
Zhen Hu Peking
Adam Hunt Princeton
On the other hand, even though Upsilon (1S) has
been discovered over 30 years ago and has been
studied extensively since then, its production
mechanism at hadron colliders is still not well
understood. It can be produced directly or
indirectly from higher excited states of
bottomonium. The cross section predictions of
the early Color Singlet Model (CSM) were an order
of magnitude lower than that measured by the
Collider Detector at Fermilab (CDF)
collaboration. While the new Color Octet
Mechanism (COM) in the framework of
Non-Relativistic QCD (NRQCD) fits the cross
section measurement well, it is in disagreement
with the polarization measurements. The Large
Hadron Collider (LHC) will produce high pT
Upsilons at a large rate and has the potential to
discriminate between the emerging new models.
Zoltan Gecse Purdue
Nuno Leonardo Purdue
Nadia Adam Princeton
Shuang Guo Peking
Analysis Strategy
Muon Efficiencies
Acceptance
Cross Section
  • number of generated Upsilons

  • number of Upsilons where both daughter muons are
    reconstructed with tracks in the silicon tracker
    with pT gt 3.5 GeV and ? lt 2.1
  • - acceptance
  • and - identification and
    trigger efficiencies
  • - corrected yield of Upsilon
    candidates in a pT bin, extracted from the fit to
    the dimuon mass distribution
  • - integrated luminosity
  • - Upsilon pT bin size
  • Efficiencies are measured with the Tag and Probe
    data driven method. Probe muons are paired with
    well identified Tag muons. Background is
    subtracted by fitting the Upsilon peak of the
    invariant mass distribution.
  • Acceptance as a function of pT and rapidity

Event Selection
  • Single muon triggered data stream
  • Two Tracker Muons of opposite charge
  • pT gt 3.5 GeV and ? lt 2.1
  • d0 lt 2 cm and z0 lt 25 cm

Cross Section Measurement with ?Ldt 1/pb at 10
TeV
Results
Dimuon Mass Fit
Systematic Uncertainties
  • Upsilon candidates are weighted to account for
    acceptance, identification and trigger
    efficiencies
  • Unbinned maximum likelihood fit of dimuon mass
  • Three double Gaussians and linear background
  • Same resolution function for the three Upsilons
  • Relative mass difference of Upsilons fixed to
    that of PDG value
  • Luminosity measurement (dominant)
  • Acceptance and efficiencies measurements
  • Tag and Probe bias (due to altered kinematic
    distributions of the probe)
  • Unknown polarization
  • Choice of probability distribution function
  • Normalized differential cross section

References
CMS Analysis Notes 2009/066, 2009/118, 2009/119
Write a Comment
User Comments (0)
About PowerShow.com