Beauty and Charm Production at the Tevatron

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Beauty and Charm Production at the Tevatron
Donatella Lucchesi INFN and University of Padova

• Introduction
• Recent advances in the theory of heavy quark
  production
• Description of the detector
• Cross sections in pp collisions
• Conclusions

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B-quark discovered - 1977
It now appears that there may be a fifth quark
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20 years late
1997 b-production cross-section were still 2X
larger than QCD prediction. At that time only a
small portion of b-hadron inclusive
cross-section pTgt6 GeV had been measured.
Is it a shape or normalization problem? What
about charm?
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The Theory
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Factorization theorem factorize physical
observable into a calculable part and
non-calculable but universal piece
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Parton Density Functions PDF
Uncertainties from one PDF fit do not always
cover differences with other fits
New PDFs with uncertainties extracted from fit
to data
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Evolution of PDF
By 2004, recalculating the cross-section with
updated PDFs increases theoretical value by
almost 2X !
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2001 KT Factorization Scheme
Standard PDFs are functions of x the fraction of
the momentum carried by parton longitudinal to
the hadron direction. Partons also have a small
transverse momentum component
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Fragmentation Functions Db?B
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Recent Theory Advances

• Next-to-leading-log resummation
• (2001)
• In pQCD calculation pawers
• of ?log(pT)/mQ modify shape of
• fragmentation function
• pTgtgtmQ large corrections
• Moment analysis (2002) Mellin
• transformation into moment
• space

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Comparison with Run I Data - NLL
Fixed order (FO) QCD NLO calculation
resummation of next-to-leading-logs (NLL) Method
of moments instead of a fragmentation model ?
better agreement with CDF and D0 data and theory
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Theory Summary

• Agreement with Run I b cross-section data for
  pTgt5.0 GeV
• has greatly improved without the need to
  invoke exotic
• sources of excess b quarks. Most of the
  improvement is
• due to improved treatment of experimental
  inputs.
• But different theoretical approaches different
• factorization schemes, FONLL calculations, new
  methods
• to extract the non-perturbative part of
  fragmentation
• function. Which is the correct approach?
• Total cross section do not depend on the
  fragmentation
• model powerful experimental test of QCD
  calculations
• Charm quark mass and production cross section are
  close to
• b quarks but fragmentation is very different ?
• test theory predictions

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The Experiments
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CDF Run II Overview
Central muon detector Prop. Chamb.
Outside Central calorimeter 5? interaction
lengths
96 layers of COT
Silicon Vertex detector 8 layers of 3-D
silicon Up to ?2 s(d0)30?m
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Measurement of J/? and b hadron Inclusive cross
section
Run I b?lX from lepton triggers to measure the b
cross section at high pT Use also fully and
partially reconstructed B (i.e. B?J/?K and
B?lDX)
Run II use the J/? from dimuon trigger to
measure the cross section at lower pT
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Run I Leptons Trigger
Select muons with pTgt12 GeV ? ? from b Main
background punchthrough hadrons and K and ?
decay in flight
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Run II Muon Trigger
Tracks reconstructed in the COT By the Level 1
Trigger eXtra Fast Tracker (XFT) . A match is
made to hits in the muon chamber (Offline
?09860.010)
Can now reach pT(J/?) 0 GeV
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Counting the J/?
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J/? Cross Section
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J/? Production
J/?, quarkonia in general bound state
non-relativistic. NRQCD LO perturbative expansion
is ?(?3s v0) as in the Color Singlet Model (CSM)
higher order ?(?3s v4). Fragmentation process ?
color octet matrix element dominate. CO matrix
elements extracted from fits to data agree well
with Run I data at high pT BUT inclusion of CO in
NRQCD leads to a prediction of increasing
transverse polarization of charmonium at high pT
Need more precise measurement Reduce the
systematic error on detector acceptance
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Separate Hb ?J/? X from Total

• The J/? inclusive cross section include
  contributions from
• Direct production
• Indirect production from decays of excited
  charmonium
• states such as ?(2s)?J/???
• Decays of B hadrons B ? J/?X

B hadrons have long lifetime, J/? from Hb?J/?X
will be displaced
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Extracting the b fraction
A maximun likehood fit to the flight path in
the transverse plane, Lxy, used to extract the
b-fraction
Prompt J/? double Gaussian resolution function
B?J/?X From MC
Parameterized background
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b-Production cross section
To extract ds/dpT(Hb) Count the observed number
of b-hadrons in a given pT(Hb) bin wij is
the fraction of b events in the ith pT(Hb) from
thejth pT(J/?) bin obtained from MC
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Charm Cross Section
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Silicon Vertex Trigger
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Charm Production in Run II
Analysis uses 5.8 pb-1 of early 2002 data
Challenges Trigger and detector not full
efficient at that time Efficiency is a
complex Function of pT, z, cot(?) and time
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Direct Charm Production in Run II
Use impact parameter of reconstructed Charm meson
FD(d0) to distinguish directly produced charm
from B?DX, FB(d0)
FD(d0) Gaussian exponential tail from Ks???
FB(d0) double exponential from Monte Carlo
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Charm Cross-Section
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Charm vs Beauty
Charm and Beauty meson cross section Data/Theory
ratios are consistent
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Summary

• Lots of theory advances
• Total inclusive b-hadron cross sections in
  agreement
• with theoretical predictions within
  uncertainties
• Charm cross section in reasonable agreement
  with
• theory and consistent with beauty meson result
• Some misteries still around
• Quarkonia production and polarization
• X(3870)

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