NLO photon parton parametrization using ee and ep data

An NLO photon parton parametrization is presented based on the existing $F_2^\gamma$ measurements from $e^+e^-$ data and the low-$x$ proton structure function from $ep$ interactions. Also included in the extraction of the NLO parton distribution functions are the dijets data coming from $\gamma p \to j_1 + j_2 +X$. The new parametrization is compared to other NLO parametrizations.Comment: 22 pages, 7 figures, 2 table

A new gamma*-p / pbar-p factorization test in diffraction, valid below Q^2 about 6 GeV^2

One of the key experimental issues in high energy hadron physics is the extent to which data from the diffractive interaction mechanism may be described by a factorized formula which is the product of a universal term describing the probability of finding a Pomeron in a proton (loosely referred to as the "Pomeron flux-factor") and a term decribing the Pomeron's interaction with the other incident proton. In the present paper, after demonstrating that existing data on diffractive gamma*-p and pbar-p interactions show that the Pomeron flux-factor is not universal, we present the results of a new test of factorization in these interactions which does not rely on universality of the flux-factor. The test is satisfied to within ~20% for 1 < Q^2 ~ 6 GeV^2 and beta < 0.2 in the gamma*-p interactions, suggesting that the resons for non-universality of the flux-factor have a limited effect on the factorization itself. However, a clear breakdown of this test is observed at larger Q^2. Kharzeev and Levin suggest that this can be attributed to the onset of QCD evolution effects in the Pomeron's structure. The breakdown occurs in a Q^2 region which agrees with their estimates of a small Pomeron size.Comment: 20 pages, 7 Encapsulated Postscript figures, LaTex, submitted to European Phisical Journal

Nucleon form factors, B-meson factories and the radiative return

The feasibility of a measurement of the electric and magnetic nucleon form factors at $B$-meson factories through the radiative return is studied. Angular distributions allow a separation of the contributions from the two form factors. The distributions are presented for the laboratory and the hadronic rest frame, and the advantages of different coordinate systems are investigated. It is demonstrated that $Q^2$ values up to 8 or even 9 GeV$^2$ are within reach. The Monte Carlo event generator PHOKHARA is extended to nucleon final states, and results are presented which include Next-to-Leading Order radiative corrections from initial-state radiation. The impact of angular cuts on rates and distributions is investigated and the relative importance of radiative corrections is analysed.Comment: 9 pages, 11 figures. Final version to appear in Eur. Phys. J.

New particle searches

This review presents recent results on new particle searches achieved at Tevatron, Hera and LEP. After a brief outline of the searches on exotic particles, results on supersymmetric particles and Higgs bosons are detailed. Near future prospects are also given.Comment: 25 pages, 11 postscript figures, typo corrections. To appear in Proceedings of XIX Lepton-Photon Symposium, Stanford, August 199

Probing the QCD equation of state with thermal photons in nucleus-nucleus collisions at RHIC

Thermal photon production at mid-rapidity in Au+Au reactions at $\sqrt{s_{NN}}$ = 200 GeV is studied in the framework of a 2D+1 hydrodynamical model that describes efficiently the bulk identified hadron spectra at RHIC. The combined thermal plus NLO pQCD photon spectrum is in good agreement with the yields measured by the PHENIX experiment for all Au+Au centralities. Within our model, we demonstrate that the correlation of the thermal photon slopes with the charged hadron multiplicity in each centrality bin provides direct empirical information on the underlying degrees of freedom and on the equation of state, $s(T)/T^3$, of the strongly interacting matter.Comment: Version to appear in EPJ-C (extended discussion and refs. and a few corrections

Flavor SU(3) analysis of charmless B meson decays to two pseudoscalar mesons

Global fits to charmless B --> PP decays in the framework of flavor SU(3) symmetry are updated and improved without reference to the \sin2\beta measured from the charmonium decay modes. Fit results directly constrain the (\bar\rho,\bar\eta) vertex of the unitarity triangle, and are used to predict the branching ratios and CP asymmetries of all decay modes, including those of the B_s system. Different schemes of SU(3) breaking in decay amplitude sizes are analyzed. The major breaking effect between strangeness-conserving and strangeness-changing decays can be accounted for by including a ratio of decay constants in tree and color-suppressed amplitudes. The possibility of having a new physics contribution to K \pi decays is also examined from the data fitting point of view.Comment: 22 pages and 2 figures; some comments and references added; more references added, version to appear in journa

Cosmic-ray physics with IceCube

IceCube as a three-dimensional air-shower array covers an energy range of the cosmic-ray spectrum from below 1 PeV to approximately 1 EeV. This talk is a brief review of the function and goals of IceTop, the surface component of the IceCube neutrino telescope. An overview of different and complementary ways that IceCube is sensitive to the primary cosmic-ray composition up to the EeV range is presented. Plans to obtain composition information in the threshold region of the detector in order to overlap with direct measurements of the primary composition in the 100-300 TeV range are also described.Comment: 12 pages, 5 figures, presented at COSPAR, Bremen Germany, 2010 Accepted for publication in Advances in Space Research. Revised version adds acknowledgmen

Triggering on hard probes in heavy ion collisions with CMS

We present a study of the CMS trigger system in heavy-ion collisions. Concentrating on two physics channels, dimuons from decays of quarkonia and single jets, we evaluate a possible trigger strategy for Pb+Pb running that relies on event selection solely in the High-Level Trigger (HLT). The study is based on measurements of the timing performance of the offline algorithms and event-size distributions using full simulations. Using a trigger simulation chain, we compare the physics reach for the jet and dimuon channels using online selection in the HLT to minimum bias running. The results demonstrate the crucial role the HLT will play for CMS heavy-ion physics.Comment: 4 pages, 4 fugures, contribution to QM'06 conferenc