6,014 research outputs found
Quarkonia production with the Hera-B experiment
Measurements of the dependence of the J/Psi production cross section on its
kinematic variables as well as on the target atomic numbers for 920 GeV/c
protons incident on different targets have been made with the Hera-B detector.
The large collected di-lepton sample allows to study the production ratio of
Psi(2S) to J/Psi and of Chic to J/Psi . We also report on measurements of the
b-bbar and Upsilon production cross section.Comment: 9 pages, 11 figure
Heavy Flavor Probes of Quark Matter
A brief survey of the role of heavy flavors as a probe of the state of matter
produced by high energy heavy ion collisions is presented. Specific examples
include energy loss, initial state gluon saturation, thermalization and flow.
The formation of quarkonium bound states from interactions in which multiple
heavy quark-antiquark pairs are initially produced is examined in general.
Results from statistical hadronization and kinetic models are summarized. New
predictions from the kinetic model for J/Psi at RHIC are presented.Comment: Based on invited plenary talk at Strange Quark Matter 2004, Cape
Town, South Africa, September 15-20, 2004, references completed, published in
J. Phys. G: Nucl. Part. Phys. 31 (2005) S641-S64
Cold nuclear effects on heavy flavours (a review)
Before wondering about the quark-gluon plasma (QGP), one has to take into
account various cold (normal) nuclear matter effects, that can be probed
through p+A like collisions. This article aims at reviewing the current results
(and understanding) of these effects on heavy quarks and quarkonia production.Comment: 8 pages, 6x2 figures, SQM08 proceedings, version accepted by
J.Phys.G. Figure 4 left and 5 right remad
Quarkonia Production in Hot and Cold Matters
Quarkonia were predicted to be suppressed in the "hot" deconfined matter
known as the Quark Gluon Plasma (QGP), but they were also seen to suffer from
"cold" nuclear matter effects (parton shadowing, nuclear absorption...). Both
at SPS and RHIC, suppression beyond nuclear effects was observed, but the
rapidity dependence of the RHIC result is not easy to interpret. I review here
the current status of these results, their possible interpretations and the new
measurements that could provide insights on quarkonia suppression. Some of them
were presented at this conference.Comment: 8 pages, 4x2 figures, to appear in the proceedings of Quark Matter
2008: 20th International Conference on Ultra-Relativistic Nucleus Nucleus
Collisions (QM 2008), Jaipur, India, 4-10 Feb 2008. Version 3 accepted by
editor. Figure 3 correcte
Heavy-flavour and quarkonium production in the LHC era: from proton-proton to heavy-ion collisions
This report reviews the study of open heavy-flavour and quarkonium production
in high-energy hadronic collisions, as tools to investigate fundamental aspects
of Quantum Chromodynamics, from the proton and nucleus structure at high energy
to deconfinement and the properties of the Quark-Gluon Plasma. Emphasis is
given to the lessons learnt from LHC Run 1 results, which are reviewed in a
global picture with the results from SPS and RHIC at lower energies, as well as
to the questions to be addressed in the future. The report covers heavy flavour
and quarkonium production in proton-proton, proton-nucleus and nucleus-nucleus
collisions. This includes discussion of the effects of hot and cold strongly
interacting matter, quarkonium photo-production in nucleus-nucleus collisions
and perspectives on the study of heavy flavour and quarkonium with upgrades of
existing experiments and new experiments. The report results from the activity
of the SaporeGravis network of the I3 Hadron Physics programme of the European
Union 7th Framework Programme
Measurement of the branching ratios of the decays Xi0 --> Sigma+ e- nubar and anti-Xi0 --> anti-Sigma+ e+ nu
From 56 days of data taking in 2002, the NA48/1 experiment observed 6316 Xi0
--> Sigma+ e- nubar candidates (with the subsequent Sigma+ --> p pi0 decay) and
555 anti-Xi0 --> anti-Sigma+ e+ nu candidates with background contamination of
215+-44 and 136+-8 events, respectively. From these samples, the branching
ratios BR(Xi0 --> Sigma+ e- nubar)= (2.51+-0.03stat+-0.09syst)E(-4) and
BR(anti-Xi0 --> anti-Sigma+ e+ nu)= (2.55+-0.14stat+-0.10syst)E(-4) were
measured allowing the determination of the CKM matrix element |Vus| =
0.209+0.023-0.028. Using the Particle Data Group average for |Vus| obtained in
semileptonic kaon decays, we measured the ratio g1/f1 = 1.20+-0.05 of the
axial-vector to vector form factors.Comment: 16 pages, 11 figures Submitted to Phys.Lett.
Measurement of the Ratio Gamma(KL -> pi+ pi-)/Gamma(KL -> pi e nu) and Extraction of the CP Violation Parameter |eta+-|
We present a measurement of the ratio of the decay rates Gamma(KL -> pi+
pi-)/Gamma(KL -> pi e nu), denoted as Gamma(K2pi)/Gamma(Ke3). The analysis is
based on data taken during a dedicated run in 1999 by the NA48 experiment at
the CERN SPS. Using a sample of 47000 K2pi and five million Ke3 decays, we find
Gamma(K2pi)/Gamma(Ke3) = (4.835 +- 0.022(stat) +- 0.016(syst)) x 10^-3. From
this we derive the branching ratio of the CP violating decay KL -> pi+ pi- and
the CP violation parameter |eta+-|. Excluding the CP conserving direct photon
emission component KL -> pi+ pi- gamma, we obtain the results BR(KL -> pi+ pi-)
= (1.941 +- 0.019) x 10^-3 and |eta+-| = (2.223 +- 0.012) x 10^-3.Comment: 20 pages, 7 figures, accepted by Phys. Lett.
First observation of the KS->pi0 gamma gamma decay
Using the NA48 detector at the CERN SPS, 31 KS->pi0 gamma gamma candidates
with an estimated background of 13.7 +- 3.2 events have been observed. This
first observation leads to a branching ratio of BR(KS->pi0 gamma gamma) = (4.9
+- 1.6(stat) +- 0.9(syst)) x 10^-8 in agreement with Chiral Perturbation theory
predictions.Comment: 10 pages, 4 figures submitted to Phys. Lett.
Measurement of the branching ratio of the decay KL -> pi e nu and extraction of the CKM parameter |Vus|
We present a new measurement of the branching ratio R of the decay KL -> pi e
nu (Ke3), relative to all charged KL decays with two tracks, based on data
taken with the NA48 detector at the CERN SPS. We measure R = 0.4978 +- 0.0035.
From this we derive the Ke3 branching fraction and the weak coupling
parameter |Vus| in the CKM matrix. We obtain |Vus|f+(0) = 0.2146 +- 0.0016,
where f+(0) is the vector form factor in the Ke3 decay.Comment: 18 pages, 8 figures. accepted by Phys Lett.
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