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

CP and T violation in (long)long baseline neutrino oscillation experiments

We consider possibilities of observing CP-violation effects in neutrino oscillation experiments with low energy ($\sim$ several hundreds MeV).Comment: 10 pages, 1 EPS figure.Talk presented at the ICFA/ECFA Workshop "Neutrino Factories based on Muon Storage Rings", nu-Fact'99, Lyon, France, 5-9 July 1999,corrected some typo

Measuring the Photon Fragmentation Function at HERA

The production of final state photons in deep inelastic scattering originates from photon radiation off leptons or quarks involved in the scattering process. Photon radiation off quarks involves a contribution from the quark-to-photon fragmentation function, corresponding to the non-perturbative transition of a hadronic jet into a single, highly energetic photon accompanied by some limited hadronic activity. Up to now, this fragmentation function was measured only in electron-positron annihilation at LEP. We demonstrate by a dedicated parton-level calculation that a competitive measurement of the quark-to-photon fragmentation function can be obtained in deep inelastic scattering at HERA. Such a measurement can be obtained by studying the photon energy spectra in $\gamma + (0+1)$-jet events, where $\gamma$ denotes a hadronic jet containing a highly energetic photon (the photon jet). Isolated photons are then defined from the photon jet by imposing a minimal photon energy fraction. For this so-called democratic clustering approach, we study the cross sections for isolated $\gamma + (0+1)$-jet and $\gamma + (1+1)$-jet production as well as for the inclusive isolated photon production in deep inelastic scattering.Comment: 23 pages, LaTe

Final state interaction effects in semi-inclusive DIS off the deuteron

The effects of the final state interaction (FSI) in semi-exclusive deep-inelastic scattering of electrons off the deuteron are analyzed paying particular attention to two extreme kinematical regions: i) the one where FSI effects are minimized, so that the quark distribution of bound nucleons could be investigated, and ii) the one where the re-interaction of the produced hadrons with the spectator nucleon is maximized, which would allow one to study the mechanism of hadronization of highly virtual quark. It is demonstrated that when the recoiling spectator nucleon is detected in the backward hemisphere with low momentum the effects from FSI are negligible, whereas at large transverse momenta of the spectator the FSI effects are rather large. Numerical estimates show that the FSI corrections are sensitive to the theoretical models of the hadronization mechanism.Comment: 18 pages 6 figures A draft of the paper was erroneously sent instead of the paper itsel

Study on Decays of DsJ∗(2317)D_{sJ}^{*}(2317) and DsJ(2460)D_{sJ}(2460) in terms of the CQM Model

Based on the assumption that $D_{sJ}^{*}(2317)$ and $D_{sJ}(2460)$ are the $(0^+, 1^+)$ chiral partners of $D_{s}$ and $D^*_s$, we evaluate the strong pionic and radiative decays of $D_{sJ}^{*}(2317)$ and $D_{sJ}(2460)$ in the Constituent Quark Meson (CQM) model. Our numerical results of the relative ratios of the decay widths are reasonably consistent with data.Comment: 12 pages, 2 figures, 4 tables, a few references adde

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.

Little Higgs models and single top production at the LHC

We investigate the corrections of the littlest Higgs(LH) model and the SU(3) simple group model to single top production at the CERN Large Hardon Collider(LHC). We find that the new gauge bosons $W_{H}^{\pm}$ predicted by the LH model can generate significant contributions to single top production via the s-channel process. The correction terms for the tree-level $Wqq'$ couplings coming from the SU(3) simple group model can give large contributions to the cross sections of the t-channel single top production process. We expect that the effects of the LH model and the SU(3) simple group model on single top production can be detected at the LHC experiments.Comment: 17pages, 5 figures, discussions and references added, typos correcte

B\Bbar mixing with the bulk fields in the Randall-Sundrum model

We calculate the B\Bbar mixing in the Randall-Sundrum bulk model. In this model, all the Standard Model fields except the Higgs can reside in the bulk. Two suggestive models of "mixed" and "relaxed" scenarios are considered. We find that the enhancement of the loop function is 0.51% for the "relaxed" and 1.07% for the "mixed" scenario when the first 4th KK modes are included, for a bulk fermion mass parameter $\nu=-0.3$.Comment: REVTEX, 20 pages, 3 figure

Quark mass dependence of pseudoscalar masses and decay constants on a lattice

Our previous calculations of the sea- and valence-quark mass dependence of the pseudoscalar meson masses and decay constants is repeated on a 16^3x32 lattice which allows for a better determination of the quantities in question. The conclusions are similar as before on the 16^4 lattice [1]. The two light dynamical quark flavours we simulate have masses in the range 1/4 m_s < m_{u,d} < 2/3 m_s. The sea quark mass dependence of f_pi and m_pi^2/m_q is well described by the next-to-leading order (NLO) Chiral Perturbation Theory (ChPT) formulas and clearly shows the presence of chiral logarithms. The valence quark mass dependence requires the presence of NNLO contributions in Partially Quenched ChPT (PQChPT) -- in addition to the NLO terms. The O(a) lattice artifacts in these quantities turn out to be small.Comment: 17 pages, 5 figure

Isospin constraints from/on B->pipi

The Standard Model constraints on alpha which can be derived from the B-> pipi decays are revisited in some depth. As experimental inputs, the three branching ratios, the two CP parameters Spipi and Cpipi and/or the value of alpha as determined by the global CKM fit are used. The constraints discussed here are model independent in the sense that they rely only on Isospin symmetry, following the Gronau-London proposal. A new bound on B00 and the function C00(B00) are introduced. The Grossman-Quinn bound is rediscussed. A close form expression is given for alpha as a function of the measurements. Various scenarii for the future of the isospin analysis are explored. To probe the Standard Model the (B00,C00) plane is introduced.Comment: 25 pages, 8 figures, Submitted to Eur. Phys. J.