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Scientific Report 2007-2009
Particle physics
P10. Study of Standard Model processes at the high energy frontier
with the CDF experiment
The Standard Model of fields and particles is the theory
that provides the best description of the known phenomenology
of the particle physics. Since its formalisation
at the end of the ’60s, the Standard Model has been
tested by many experiments. In this process a key role
is played by the collision experiments in which elementary
particles (tipically electrons and protons) interact
at high energy, allowing precise tests of the theoretical
models. In the latest years the TeVatron accelerator
(located at the Fermi National Accelerator Laboratory,
near Chicago) provided p¯p collisions at √ s = 1.96 TeV,
the highest available energy before the Large Hadron
Collider at Cern will be fully operational. The CDF experiment
runs one of the two multi-purpouse detectors
installed at the TeVatron and is performing a wide range
of measurements of SM processes generated by p¯p interactions
with high tensferred momentum. In particular
all the processes in which top quarks or Vector Bosons
are produced require high energy partons interaction.
The top quark has been discovered by the first run of
the TeVatron experiments in 1996, exploiting the pair
production process. After 13 years, in 2009, during the
second run of the TeVatron, also the electroweak single
top quark production has been observed.
The study of the associate production of Vector Boson
and jets in p¯p collisions, is a fundamental tool to test the
QCD in high transferred momentum regime, and can
provide information on proton structure function.
of the jets have been performed. These results provide
strong tests of the theoretical predictions and are also
fundamental in order to tune the Monte Carlo generators
for the next generation of experiments.
Exploiting techniques for the identification of the
flavour of the parton which originates a jet, the production
cross section of W + b, W + c, and Z + b processes
have been measured, providing results in good agreement
with the SM expectations.
× BR(Z→ee) [fb]
σ N
jets
Ratio to LO
5
10
4
10
10
3
2
10
1.8
1.6
1.4
1.2
1
Z→ee + jets
2
66 < M ee < 116 GeV/c
e
e
E T > 25 GeV, | η 1 | < 1
e
e
|η 2 | < 1 || 1.2 < |η 2 | < 2.8
jet
jet
p T > 30 GeV/c, |y | < 2.1
∆R(e,jet) > 0.7
1 2 3
CDF Run II Preliminary
-1
CDF Data L = 1.7 fb
Systematic uncertainties
NLO MCFM CTEQ6.1M
corrected to hadron level
2 2 2
µ 0 = M Z + p T (Z), R sep =1.3
NLO scale µ = 2µ 0 ; µ = µ 0 /2
NLO PDF uncertainties
LO MCFM hadron level
≥ N jets
Figure 1: Measured cross section as a function of inclusive
jet multiplicity compared to NLO QCD predictions [2].
Figure 2: Dijet invariant mass distribution for candidates
diboson events selected in the missing transvers energy and
two jets final state [3].
The large statistic sample collected in the last years
has allowed CDF experiment to reach competitive
results also in the diboson sector, both in the cross
section measurements and in the Triple Gauge Coupling
limits. Several final states have been succesfully studied,
including the hadronic ones, which are also relevant for
the study of the low mass Higgs Boson.
References
1. T. Aaltonen et al., Phys. Rev. D 77, 011108 (2008).
2. T. Aaltonen et al., Phys. Rev. Lett. 100, 102001 (2008).
3. T. Aaltonen et al., Phys. Rev. Lett. 103, 091803 (2009).
4. T. Aaltonen et al., Phys. Rev. D 79, 052008 (2009).
Authors
C. Dionisi, S. Giagu, M. Iori, C. Luci, P. Mastrandrea 1 , M.
Rescigno 1 , L. Zanello
In the latest years, with the increasing integrated luminosity
collected by the CDF detector, differential measurements
of the production cross sections of Z/W + jet
as a function of the number, momentum and rapidity
http://www.roma1.infn.it/exp/cdf/
Sapienza Università di Roma 117 Dipartimento di Fisica