20,723 research outputs found
Quaero@H1: An Interface to High-pT HERA Event Data
Distributions from high-pT HERA event data analyzed in a general search for
new physics at H1 have been incorporated into Quaero, an algorithm designed to
automate tests of specific hypotheses with high energy collider data. The use
of Quaero@H1 to search for leptoquarks, R-parity violating supersymmetry, and
excited quarks provides examples to develop intuition for the algorithm's
performance.Comment: Submitted to Eur. Phys. J.
Strange Particle Production in p+p, p+Pb and Pb+Pb Interactions from NA49
Recent NA49 results on Lambda, Antilambda, Xi- and Antixi+ production in
minimum bias p+p and centrality selected p+Pb collisions at 158 GeV/c, and the
results on Lambda, Antilambda, K+ and K- production in central Pb+Pb collisions
at 40, 80 and 158 A GeV are discussed and compared with other available data.
By comparing the energy dependence of Lambda and Antilambda production at
mid-rapidity a striking similarity is observed between p+p and A+A data. This
is also seen in the energy dependence of the Lambda/pi ratio. K+/pi at
mid-rapidity is affected in a similar way, due to the associated production of
K+ together with Lambda particles. The observed yields increase faster than the
number of wounded nucleons when comparing p+Pb to p+p. As already observed in
A+A collisions, the increase is larger for multistrange than for strange
baryons and for baryons than for anti-baryons.Comment: 8 pages, 10 figures, To appear in proceedings of Strange Quark in
Matter 2001-A Flavourspace Odyssey, Frankfurt am Main, Germany, 24-29. Sept.
200
Azimuth Quadrupole Systematics in Au-Au Collisions
We have measured -dependent two-particle number correlations on azimuth
and pseudorapidity for eleven centralities of and 200~GeV
Au-Au collisions at STAR. 2D fits to these angular correlations isolate the
azimuth quadrupole amplitude, denoted , from
localized same-side correlations. Event-plane measurements within
the STAR TPC acceptance can be expressed as a sum of the azimuth quadrupole and
the quadrupole component of the same-side peak. can be
transformed to reveal quadrupole spectra which are approximately
described by a fixed transverse boost and universal L\'evy form nearly
independent of centrality. A parametrization of can be
factored into centrality and -dependent pieces with a simple
dependence above 0.75 GeV/c. Results from STAR are compared to published data
and model predictions.Comment: Conference proceedings for Hot Quarks 201
Photon-tagged jet measurements in Pb+Pb collisions with the CMS detector
Presented are the results of a detailed study for a complete simulation of
the CMS detectors at the LHC in view of the expected modification of jet
fragmentation functions in central Pb+Pb collisions at (s_NN)**0.5=5.5 TeV
compared to the vacuum (p+p) case. The study is based on photon-jet events,
using the correlation between isolated high-transverse energy (E_T>70 GeV)
photons and fully reconstructed jets, based on the information provided by the
CMS calorimeters and silicon tracker.Comment: 4 pages, 4 figures, ontribution to QM'08 conferenc
Resolved photon and multi-component model for p and scattering at high energies
We generalize our previous model for scattering to scattering. In the latter case the number of components naturally
grows. When using the model parameters from our previous analysis
the model cross section for scattering is larger than the
corresponding LEP2 experimental data by more than a factor of two. However,
performing a new simultaneous fit to and total
cross section we can find an optimal set of parameters to describe both
processes. We propose new measures of factorization breaking for collisions and present results for our new model.Comment: 23 pages, 10 figure
Air Shower Measurements in the Primary Energy Range from PeV to EeV
Recent results of advanced experiments with sophisticated measurements of
cosmic rays in the energy range of the so called knee at a few PeV indicate a
distinct knee in the energy spectra of light primary cosmic rays and an
increasing dominance of heavy ones towards higher energies. This leads to the
expectation of knee-like features of the heavy primaries at around 100 PeV. To
investigate in detail this energy region several new experiments are or will be
devised.Comment: 4 pages; submitted to Proceedings of 2nd Workshop on TeV
Astrophysics, Aug 28-31, 2006, Madison, W
Constraining the time variation of the coupling constants from cosmic microwave background: effect of \Lambda_{QCD}
We investigate constraints on the time variation of the fine structure
constant between the recombination epoch and the present epoch,
\Delta\alpha/\alpha \equiv (\alpha_{rec} - \alpha_{now})/\alpha_{now}, from
cosmic microwave background (CMB) taking into account simultaneous variation of
other physical constants, namely the electron mass m_{e} and the proton mass
m_{p}. In other words, we consider the variation of Yukawa coupling and the QCD
scale \Lambda_{QCD} in addition to the electromagnetic coupling. We clarify
which parameters can be determined from CMB temperature anisotropy in terms of
singular value decomposition. Assuming a relation among variations of coupling
constants governed by a single scalar field (the dilaton), the 95% confidence
level (C.L.) constraint on \Delta\alpha/\alpha is found to be -8.28 \times
10^{-3} < \Delta\alpha/\alpha < 1.81 \times 10^{-3}, which is tighter than the
one obtained by considering only the change of \alpha and m_{e}. We also obtain
the constraint on the time variation of the proton-to-electron mass ratio \mu
\equiv m_{p}/m_{e} to be -0.52 < \Delta\mu/\mu < 0.17 (95% C.L.) under the same
assumption. Finally, we also implement a forecast for constraints from the
PLANCK survey.Comment: 25 pages, 4 figures; references adde
Antikaon-nucleus dynamics: from quasibound states to kaon condensation
Coupled-channel Kbar-N dynamics near threshold and its repercussions in
few-body Kbar-nuclear systems are briefly reviewed, highlighting studies of a
K^-pp quasibound state. In heavier nuclei, the extension of mean-field
calculations to multi-Kbar nuclear and hypernuclear quasibound states is
discussed. It is concluded that strangeness in finite self-bound systems is
realized through hyperons, with no room for kaon condensation.Comment: Proceedings version of plenary talk at Quark Nuclear Physics (QNP09)
September 2009, Beijing; matches published versio
Prospects for top-prime quark discovery at the Tevatron
We show that a top-prime quark as heavy as 600 GeV can be discovered at the
Tevatron, provided it is resonantly pair-produced via a vector color octet. If
the top-prime originates from a vectorlike quark, then the production of a
single top-prime in association with a top may also be observable, even through
its decay into a Higgs boson and a top. A color octet with mass of about 1 TeV,
which decays into a top-prime pair, may account for the CDF excess of
semileptonic (Wj)(Wj) events.Comment: 22 pages, 6 ps figures. v2: Note added about the new D0 search for
(Wb)(Wb) resonances; section 4.1 expanded; single-top constraint updated in
section 2; references adde
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