Recently, it has been shown, contrary to previous beliefs, that the ${\mathit{k}}_{\perp }$ distribution of quarks in a transversely polarized proton can be asymmetric. This “Sivers effect” had already been used to explain transverse single spin asymmetry (SSA) observed in inclusive pion production $p^{\uparrow }\overrightarrow{p}\pi X$ and $p^{\uparrow }\overrightarrow{p}\pi X.\mathrm{}$ In such channels, however, other mechanisms, such as the “Collins effect” (a ${\mathit{k}}_{\perp }$ asymmetric fragmentation of a transversely polarized quark into pions), may generate SSA. The Sivers asymmetry is used here to compute the SSA in Drell-Yan processes; in this case, by considering the differential cross section in the lepton-pair invariant mass, rapidity, and transverse momentum, other mechanisms that may originate SSA cannot contribute. Estimates for BNL RHIC experiments are given.

Baryon number inhomogeneities may be generated during the epoch when the baryon asymmetry of the universe is produced, e.g. at the electroweak phase transition. The regions with excess baryon number will have a lower temperature than the background temperature of the universe. Also the value of the quark hadron transition temperature $T_c$ will be different in these regions as compared to the background region. Since a first-order quark hadron transition is very susceptible to small changes in temperature, we investigate the effect of the presence of such baryonic lumps on the dynamics of the quark-hadron transition. We find that the phase transition is delayed in these lumps for significant overdensities. Consequently, we argue that baryon concentration in these regions grows by the end of the transition. We briefly discuss some models which may give rise to such high overdensities at the onset of the quark-hadron transition.

The lepton helicity distributions in the polarized Drell-Yan process at BNL RHIC energy are investigated. For events with a relatively low invariant mass of a lepton pair in which the weak interaction is negligible, only a measurement of lepton helicity can prove the antisymmetric part of the hadronic tensor. Therefore it might be interesting to consider the helicity distributions of leptons to obtain more information on the structure of the nucleon from the polarized Drell-Yan process. We estimate the QCD corrections at the $\mathcal{O}\left({\alpha }_s\right)$ level to the hadronic tensor including both intermediate γ and Z bosons. We present numerical analyses for different invariant masses and show that the u $\left(ū\right)$ and d $\left(\overline{d}\right)$ quarks give different and characteristic contributions to the lepton helicity distributions. We also estimate the lepton helicity asymmetry for the various proton spin configurations.

There are nonradial null geodesics emanating from the shell focusing singularity formed at the symmetric center in a spherically symmetric dust collapse. In this article, assuming self-similarity in the region filled with the dust fluid, we study these singular null geodesics in detail. We see the time evolution of the angular diameter of the central naked singularity and show that it might be bounded above by a value corresponding to the circular null geodesic in the Schwarzschild spacetime. We also investigate the angular frequency of the physical field that propagates along the singular null geodesic and find that it depends on the impact parameter. Further, we comment on the nonuniformity of the topology of the central naked singularity.

In a recent investigation of the effects of precession on the anticipated detection of gravitational-wave inspiral signals from compact object binaries with moderate total masses $\lesssim 10M_{\odot },$ we found that (i) if precession is ignored, the inspiral detection rate can decrease by almost a factor of 10, and (ii) previously proposed “mimic” templates cannot improve the detection rate significantly (by more than a factor of 2). In this paper we propose a new family of templates that can improve the detection rate by a factor of 5 or 6 in cases where precession is most important. Our proposed method for these new “mimic” templates involves a hierarchical scheme of efficient, two-parameter template searches that can account for a sequence of spikes that appear in the residual inspiral phase, after one corrects for any oscillatory modification in the phase. We present our results for two cases of compact object masses (10 and $1.4{\mathrm{M}}_{\odot }$ and 7 and $3{\mathrm{M}}_{\odot })$ as a function of spin properties. Although further work is needed to fully assess the computational efficiency of this newly proposed template family, we conclude that these “spiky templates” are good candidates for a family of precession templates used in realistic searches that can improve detection rates of inspiral events.

The explanation of various observed phenomena such as large angle neutrino oscillations, hierarchies of charged fermion masses and CKM mixings, and apparent baryon number conservation may have a common origin. We show how this could occur in 5D SUSY SU(5) supplemented by a $\mathcal{U}\mathrm{}\left(1\right)\mathrm{}$ flavor symmetry and additional matter supermultiplets called “copies.” In addition, the proton decays into $\overrightarrow{p}K\nu ,$ with an estimated lifetime of the order of ${10}^{33}-{10}^{36}\mathrm{yr}.$ Other decay channels include $\mathrm{Ke}$ and $K\mu$ with comparable rates. We also expect that $\mathrm{BR}\left(\overrightarrow{\mu }e\gamma \right)\sim \mathrm{BR}\left(\overrightarrow{\tau }\mu \gamma \right).\mathrm{}$

The complete next-to-leading order (NLO) QCD corrections to charged Higgs boson associated production with a top quark through $b\overrightarrow{g}{\mathrm{tH}}^{-}$ at the CERN Large Hadron Collider are calculated in the minimal supersymmetric standard model and two-Higgs-doublet model in the $\overline{\mathrm{MS}}$ scheme. The NLO QCD corrections can reduce the scale dependence of the leading order (LO) cross section. The K factor (defined as the ratio of the NLO cross section to the LO one) does not depend on $\tan \beta$ if the same quark running masses are used in the NLO and LO cross sections, and varies roughly from ∼1.6 to ∼1.8 when charged Higgs boson mass increases from 200 to 1000 GeV.

We present results for the mass of the ${\eta }^{\prime }$ meson in the continuum limit for two-flavor lattice QCD, calculated on the CP-PACS computer, using a renormalization-group-improved gauge action, and the Sheikoleslami-Wohlert fermion action with a tadpole-improved $c_{\mathrm{sw}}.$ The correlation functions are measured at three values of the coupling β corresponding to the lattice spacing $a\approx 0.22,$ 0.16, 0.11 fm and for four values of the quark mass parameter κ corresponding to $m_{\pi }{/m}_{\rho }\approx 0.8,$ 0.75, 0.7, 0.6. For each (β, κ) pair, 400–800 gauge configurations are used. The two-loop diagrams are evaluated using a noisy source method. We calculate ${\eta }^{\prime }$ propagators using both smeared and local sources, and find that excited state contaminations are much reduced by smearing. A full analysis for the smeared propagators gives $m_{{\eta }^{\prime }}{=0.960\mathrm{}\left(87\right)\mathrm{}}_{-0.248}^{+0.036\mathrm{}}\mathrm{GeV}$ in the continuum limit, where the second error represents the systematic uncertainty coming from varying the functional form for chiral and continuum extrapolations.

An investigation of the s-wave channels in meson-meson scattering is performed within a $U\left(3\right)\mathrm{}$ chiral unitary approach. Our calculations are based on a chiral effective Lagrangian which includes the ${\eta }^{\prime }$ as an explicit degree of freedom and incorporates important features of the underlying QCD Lagrangian such as the axial $U\left(1\right)\mathrm{}$ anomaly. We employ a coupled channel Bethe-Salpeter equation to generate poles from composed states of two pseudoscalar mesons. Our results are compared with experimental phase shifts up to 1.5 GeV and effects of the ${\eta }^{\prime }$ within this scheme are discussed.

The ALEPH data on hadronic $\tau$ decay are thoroughly analyzed in the framework of QCD. The perturbative calculations are performed in the (1–4)-loop approximation. The analytical properties of the polarization operators are used in the whole complex $q^2$ plane. It is shown that the QCD prediction for $R_{\tau }$ agrees with the measured value $R_{\tau }$ not only for conventional ${\Lambda }_3^{\mathrm{conv}}=(618\mathrm{}\pm 29)\mathrm{MeV}$ but also for ${\Lambda }_3^{\mathrm{new}}=(1666\mathrm{}\pm 7)\mathrm{MeV}.$ The polarization operator calculated using the renormalization group has a nonphysical cut $[-{\Lambda }_3^2,0\mathrm{}].$ If ${\Lambda }_3={\Lambda }_3^{\mathrm{conv}},$ the contribution of only the physical cut is deficient in the explanation of the ALEPH experiment. If ${\Lambda }_3={\Lambda }_3^{\mathrm{new}}$ the contribution of the nonphysical cut is very small and only the physical cut explains the ALEPH experiment. The new sum rules which follow only from analytical properties of polarization operators are obtained. Based on the sum rules obtained, it is shown that there is an essential disagreement between QCD perturbation theory and the $\tau$-lepton hadronic decay experiment at the conventional value ${\Lambda }_3.$ In the evolution upwards to larger energies the matching of ${r(q}^2)$ at the masses $J/\psi ,$ ${\rm Y},$ and ${2m}_t$ was performed. The obtained value ${\alpha }_s\left(-m_z^2\right)=0.141\mathrm{}\pm 0.004$ (at ${\Lambda }_3={\Lambda }_3^{\mathrm{new}})$ differs essentially from the conventional value, but the calculation of the values $R\left(s\right)=\sigma {(e}^{+}{e}^{-}\to \mathrm{hadrons})/\sigma {(e}^{+}{e}^{-}\to {\mu }^{+}{\mu }^{-}),$ $R_l=\Gamma \left(\overrightarrow{Z}\mathrm{hadrons}\right)/\Gamma \left(\overrightarrow{Z}\mathrm{leptons}\right),$ ${\alpha }_s\left(-3{\mathrm{GeV}}^2\right),$ and ${\alpha }_s\left(-2.5{\mathrm{GeV}}^2\right)$ does not contradict the experiments.

The effects of strong interactions on the two-loop electroweak radiative corrections to the muon anomalous magnetic moment, $a_{\mu }{=(g}_{\mu }-2)/2,$ are examined. Short-distance logarithms are shown to be unaffected. The computation of long-distance contributions is improved by the use of an effective field theory approach that preserves the chiral properties of QCD and accounts for constraints from the operator product expansion. Small, previously neglected, two-loop contributions, suppressed by a $1-4{\sin }^2{\theta }_W$ factor, are computed and the complete three-loop leading short-distance logarithms are reevaluated. These refinements lead to a reduction in uncertainties and a slight shift in the total electroweak contribution to $a_{\mu }^{\mathrm{EW}}=154\mathrm{}\left(1\right)\mathrm{}\left(2\right)\mathrm{}\times {10}^{-11}$ where the first error corresponds to hadronic uncertainties and the second is primarily due to the allowed Higgs boson mass range.

We calculate the time delays of neutrinos emitted in gamma ray bursts due to the effects of neutrino mass and quantum gravity using a time dependent Hubble constant which can significantly change the naive results presented hitherto in the literature for large redshifts, and gives some sensitivity to the details of dark energy. We show that the effects of neutrino mass, quantum gravity and dark energy may be disentangled by using low energy neutrinos to study neutrino mass, high energy neutrinos to study quantum gravity, and large redshifts to study dark energy. From low energy neutrinos one may obtain direct limits on neutrino masses of order ${10}^{-3}\mathrm{eV},$ and distinguish a neutrino mass hierarchy from an inverted mass hierarchy. From ultra-high energy neutrinos the sensitivity to the scale of quantum gravity can be pushed up to $E_{\mathrm{QG}}\sim 5\times {10}^{30}\mathrm{GeV}.$ By studying neutrinos from GRBs at large redshifts a cosmological constant could be distinguished from quintessence.

Neutrino Majorana masses and mixings can be generated from a dimension-5 operator within the standard model particle content. After a review of the mechanism of radiative enhancement of the mixing angle in a two-neutrino case, we consider three-flavor mass matrices of two-zero texture generated from such an operator and investigate the possibility of implementing the mechanism here. We observe that radiative magnification of only the solar angle is consistent with oscillation data on masses and mixings, and that too for nearly degenerate neutrinos, with two of them having opposite $\mathrm{CP}$ parities, while for hierarchical masses the mechanism does not work. In supersymmetry or in an extra-dimensional scenario the above features are qualitatively unchanged.

Recently the full $O({\alpha }_S^{5}m,{\alpha }_S^{5}m\log {\alpha }_S)$ correction to the heavy quarkonium $1S$ energy level has been computed (except the $a_3$ term in the QCD potential). We point out that the full correction (including the $\log {\alpha }_S$ term) is approximated well by the large-${\beta }_0$ approximation. Based on the assumption that this feature holds up to higher orders, we discuss why the top quark pole mass cannot be determined to better than $O\left({\Lambda }_{\mathrm{QCD}}\right)$ accuracy at a future $e^{+}{e}^{-}$ collider, while the modified minimal-subtraction $\left(\overline{\mathrm{MS}}\right)$ mass can be determined to about 40 MeV accuracy (provided the 4-loop $\overline{\mathrm{MS}}$-pole mass relation will be computed in due time).

We analyze $B_d^0-B_d^0$ mixing and the $B_d\to J/\psi K_S$ asymmetry in a fully left-right supersymmetric model. We give explicit expressions for all the chargino, gluino, gluino-neutralino and neutralino amplitudes involved in $B_d^0-B_d^0$ mixing. We calculate the mass difference $\Delta m_{B_d}$ and the CP asymmetry $a_{J/\psi K_S},$ allowing for supersymmetric sources of flavor violation arising from squark mixings. We obtain conservative constraints on the various squark mass splittings and compare these with analyses performed in other models.

We argue that lattice calculations of the ${\eta }^{\prime }$ mass in QCD with $N_c=2\mathrm{}$ colors performed at a nonzero baryon chemical potential can be used to study the mechanism responsible for the mass of the ${\eta }^{\prime }.$ QCD with two colors is an ideal laboratory because it exhibits confinement, chiral symmetry breaking and a would-be ${U\left(1\right)\mathrm{}}_A$ Goldstone boson at all densities. Since the instanton density and the confinement scale vary with density in a very different way, instantons are clearly distinguishable from other possible mechanisms. There is an instanton prediction for the ${\eta }^{\prime }$ mass at large density that can be compared to lattice results. The density dependence of the instanton contribution is a simple consequence of the integer topological charge carried by the instanton. We also argue that $N_c=3\mathrm{}$ color QCD at finite isospin density can be used in order to study the origin of OZI violation in the scalar sector.

The masses of heavy baryons containing a b quark have been calculated numerically in lattice QCD with pion masses which are much larger than the physical value. In the present work we extrapolate these lattice data to the physical mass of the pion by applying an effective chiral Lagrangian for heavy baryons, which is invariant under chiral symmetry when the light quark masses go to zero and heavy quark symmetry when the heavy quark masses go to infinity. A phenomenological functional form with three parameters, which has the correct behavior in the chiral limit and appropriate behavior when the pion mass is large, is proposed to extrapolate the lattice data. It is found that the extrapolation deviates noticeably from the naive linear extrapolation when the pion mass is smaller than about 500 MeV. The mass differences between ${\Sigma }_b$ and ${\Sigma }_b^{*}$ and between ${\Sigma }_b^{\left(*\right)}$ and ${\Lambda }_b$ are also presented. Uncertainties arising from both lattice data and our model parameters are discussed in detail. We also give a comparison of the results in our model with those obtained in the naive linear extrapolations.

A modified method for calculating the nonperturbative quark vacuum condensates from the global color symmetry model is derived. Within this approach it is shown that the vacuum condensates are free of ultraviolet divergence which is different from previous studies. As special cases, the two-quark condensate $〈\overline{q}q〉$ and the mixed quark-gluon condensate $g〈\overline{q}{G}_{\mu \nu }{\sigma }^{\mu \nu }q〉$ are calculated. A comparison with the results of other nonperturbative QCD approaches is given.

We discuss photon bremsstrahlung induced by virtual graviton exchange in proton-proton interactions at hadronic colliders, resulting from the exchange of Kaluza-Klein excitations of the graviton. The relevant subprocesses $g\overrightarrow{g}\overrightarrow{G}{e}^{+}{e}^{-}\gamma$ and $q\overline{q}\to e^{+}{e}^{-}\gamma$ are discussed in both the Arkani-Hamed–Dimopoulos–Dvali and the Randall-Sundrum scenarios. Although two-body final states (or real graviton emission) would presumably be the main discovery channels, a search for three-body final states could be worthwhile since such events have characteristic features that could provide additional confirmation. In particular, the $k_{\perp }$ distribution of the photon is in both scenarios harder than that of the standard-model background.

We calculate the mass distribution $\left(d\sigma {/dM}_X\right)$ as observed by the UA8 Collaboration in the inclusive reaction $p\overline{p}\to \mathrm{pX}\overline{p}$ at $\sqrt{s}=630\mathrm{}\mathrm{GeV},$ using the interacting gluon model (IGM) with double Pomeron exchange (DPE) included. The only new parameter is the $P-P$ cross section, which we can extract from fitting experimental data. We compare our results with the values obtained in the UA8 study. Assuming a constant Pomeron-Pomeron total cross section $({\sigma }_{\mathrm{PP}}=1\mathrm{}\mathrm{mb}),$ we make predictions for $d\sigma {/dM}_X$ at Fermilab Tevatron and CERN LHC energies.