17,867,436 research outputs found
Probing New Physics from Top-charm Associated Productions at Linear Colliders
The top-charm associated productions via , and collisions at linear colliders, which are extremely suppressed in the
Standard Model (SM), could be significantly enhanced in some extensions of the
SM. In this article we calculate the full contribution of the topcolor-assisted
technicolor (TC2) to these productions and then compare the results with the
existing predictions of the SM, the general two-Higgs-doublet model and the
Minimal Supersymmetric Model. We find that the TC2 model predicts much larger
production rates than other models and the largest-rate channel is , which exceeds 10 fb for a large part of the parameter
space. From the analysis of the observability of such productions at the future
linear colliders, we find that the predictions of the TC2 model can reach the
observable level for a large part of the parameter space while the predictions
of other models are hardly accessible.Comment: discussions added (version in Eur. Phys. J. C
Non-abelian color dielectric - towards the effective model of the low energy QCD
Lattice motivated triplet color scalar field theory is analyzed. We consider
non-minimal as well as covariant derivative coupling with SU(2) gauge fields.
Field configurations generated by external electric sources are presented.
Moreover non-Abelian magnetic monopoles are found. Dependence on the spatial
coordinates in the obtained solutions is identical as in the usual Abelian
case. We show also that after a decomposition of the fields a modified
Faddeev-Niemi action can be obtained. It contains explicit O(3) symmetry
breaking term parameterized by the condensate of an isoscalar field. Due to
that Goldstone bosons observed in the original Faddeev-Niemi model are removed.Comment: 19 page
Heavy Quark Interactions in Finite Temperature QCD
We study the free energy of a heavy quark-antiquark pair in a thermal medium.
We constuct a simple ansatz for the free energy for two quark flavors motivated
by the Debye-H\"uckel theory of screening.Comment: 4 pages, 4 figures, contribution to the proceedings of the
International Conference on Hard and Electromagnetic Probes of High Energy
Nuclear Collisions, Ericeira, Portugal, Nov. 4-10, 200
Two-pion Bose-Einstein correlations in central Pb-Pb collisions at = 2.76 TeV
The first measurement of two-pion Bose-Einstein correlations in central Pb-Pb
collisions at TeV at the Large Hadron Collider is
presented. We observe a growing trend with energy now not only for the
longitudinal and the outward but also for the sideward pion source radius. The
pion homogeneity volume and the decoupling time are significantly larger than
those measured at RHIC.Comment: 17 pages, 5 captioned figures, 1 table, authors from page 12,
published version, figures at
http://aliceinfo.cern.ch/ArtSubmission/node/388
Gluonic Dissociation Revisited : I. Fugacity, Flux And Formation Time Effects
We revisit the standard treatment [Xu, Kharzeev, Satz and Wang, Phys. Rev. C
{\bf 53}, 3051 (1996)] of suppression due to gluonic bombardment in an
equilibrating quark-gluon plasma. Effects arising from gluon fugacity, relative
flux, and meson formation time are correctly incorporated in
the formulation of the gluon number density, velocity-weighted cross section,
and the survival probability. Our new formulae are applied to numerically study
the pattern of suppression in the central rapidity region at RHIC/LHC
energies. The temperature and transverse momentum dependence of our graphs have
noticeable differences from those of Xu et al.Comment: 15 pages, 6 figure
Modeling the Pion and Kaon Form Factors in the Timelike Region
New, accurate measurements of the pion and kaon electromagnetic form factors
are expected in the near future from experiments at electron-positron
colliders,using the radiative return method. We construct a model for the
timelike pion electromagnetic form factor, that is valid also at momentum
transfers far above the resonance. The ansatz is based on vector
dominance and includes a pattern of radial excitations expected from dual
resonance models.The form factor is fitted to the existing data in the timelike
region, continued to the spacelike region and compared with the measurements
there and with the QCD predictions. Furthermore, the model is extended to the
kaon electromagnetic form factor. Using isospin and SU(3)-flavour symmetry
relations we extract the isospin-one contribution and predict the kaon weak
form factor accessible in semileptonic decays.Comment: 31 pages, 7 figures,latex, one reference changed, version to appear
in Eur.Phys.J
Suppression of charged particle production at large transverse momentum in central Pb-Pb collisions at TeV
Inclusive transverse momentum spectra of primary charged particles in Pb-Pb
collisions at = 2.76 TeV have been measured by the ALICE
Collaboration at the LHC. The data are presented for central and peripheral
collisions, corresponding to 0-5% and 70-80% of the hadronic Pb-Pb cross
section. The measured charged particle spectra in and GeV/ are compared to the expectation in pp collisions at the same
, scaled by the number of underlying nucleon-nucleon
collisions. The comparison is expressed in terms of the nuclear modification
factor . The result indicates only weak medium effects ( 0.7) in peripheral collisions. In central collisions,
reaches a minimum of about 0.14 at -7GeV/ and increases
significantly at larger . The measured suppression of high- particles is stronger than that observed at lower collision energies,
indicating that a very dense medium is formed in central Pb-Pb collisions at
the LHC.Comment: 15 pages, 5 captioned figures, 3 tables, authors from page 10,
published version, figures at http://aliceinfo.cern.ch/ArtSubmission/node/98
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