We study the Drell-Yan production and corresponding decay signatures at the CERN Large Hadron Collider (LHC) of extra Z bosons from a superstring-inspired $E_6$ model characterized by an extra inert $\mathrm{SU}{\mathrm{}\left(2\right)\mathrm{}}_I$ group at electroweak energies, and from the $\mathrm{Sp}{\mathrm{}\left(6\right)\mathrm{}}_L\otimes \mathrm{U}{\mathrm{}\left(1\right)\mathrm{}}_Y$ model. We discuss how to distinguish the models by examining the extra Z-boson couplings to fermions through its leptonic decay modes and muon-pair forward-backward asymmetries.

We extend the calculations of the spin alignments of vector mesons in $e^{+}{e}^{-}$ annihilation in a recent Rapid Communication to deeply inelastic lepton-nucleon scatterings. We present the results for different mesons in the current fragmentation regions of ${\mu }^{-}\overrightarrow{N}{\mu }^{-}\mathrm{VX}$ at high energies and ${\nu }_{\mu }\overrightarrow{N}{\mu }^{-}\mathrm{VX}$ at both high and low energies. We also present the predictions for ${\nu }_{\mu }\overrightarrow{N}{\mu }^{-}\mathrm{VX}$ at NOMAD energies in the target fragmentation region using a valence quark model.

We discuss periodic compactification and latticization of a 5D $U\left(1\right)\mathrm{}$ theory with a Dirac fermion, yielding a $1+3$ effective theory. We address subtleties in the lattice fermionic action, such as fermion doubling and the Wilson term. We compute the Coleman-Weinberg potential for the Wilson line which is finite for N-branes $>~3,$ due to the $Z_N$ symmetry, which replaces translations in the $5\mathrm{th}$ dimension. This mode becomes a PNGB in the low energy $1+3$ theory. We derive its anomalous coupling to the “photon” and its KK modes.

We obtain positronium hyperfine splitting owing to the noncommutativity of space and show that, to leading order, it is proportional to $\theta {\alpha }^6$ where $\theta$ is the parameter of noncommutativity. It is also shown that spatial noncommutativity splits the spacing between $n=2\mathrm{}$ triplet excited levels ${E(2\mathrm{}}^3{S}_1)\to {E(2\mathrm{}}^3{P}_2),$ which provides an experimental test of the noncommutativity of space.

A radiatively corrected mixing angle has to be independent of the choice of renormalization scale to be a physical observable. At one loop in the $\overline{\mathrm{MS}},$ this occurs for a particular value $p_{*}$ of the external momentum in the two-point functions used to define the mixing angle: $p_{*}^2{=(M}_1^2{+M}_2^2)/2,$ where $M_{1,2}$ are the physical masses of the two mixed particles. We examine two important applications of this to the minimal supersymmetric standard model: the mixing angle for (a) neutral Higgs bosons and (b) top squarks. We find that this choice of external momentum improves the scale independence (and therefore provides a more reliable determination) of these mixing angles.

We consider the universal extra dimensions scenario of Appelquist, Cheng, and Dobrescu, in which all of the standard model fields propagate into one extra compact dimension, estimated therein to be as large as $\sim (350\mathrm{}\hspace{0.5em}\mathrm{GeV}{)}^{-1}.$ Tree-level Klauza-Klein (KK) number conservation dictates that the associated KK excitations cannot be singly produced. We calculate the cross sections for the direct production of KK excitations of the gluon, $g_n^{\star },$ and two distinct towers of quarks, $q_n^{•}$ and $q_n°,$ in proton-antiproton collisions at the Fermilab Tevatron run I and II energies in addition to proton-proton collisions at the CERN Large Hadron Collider energy. The experimental signatures for these processes depend on the stability of the lowest-lying KK excitations of the gluons and light quarks. We find that the Tevatron run I mass bound for KK quark and gluon final states is about $350–400\hspace{0.5em}\mathrm{GeV},$ while run II can push this up to $450–500\hspace{0.5em}\mathrm{GeV}$ at its initial luminosity and $500–550\hspace{0.5em}\mathrm{GeV}$ if the projected final luminosity is reached. The LHC can probe much further: The LHC will either discover universal extra dimension (UED) KK excitations of quarks and gluons or extend the mass limit to about 3 TeV.

A supersymmetric standard model with two Higgs doublets and two Higgs singlets is investigated if it can accommodate the possibility of spontaneous $\mathrm{CP}$ violation. Assuming the degeneracy of the scalar quark masses of the third generation, we find that spontaneous $\mathrm{CP}$ violation in the Higgs sector is viable in our model. In the case of spontaneous $\mathrm{CP}$ violation, the masses of the lightest two neutral Higgs bosons are estimated to be 80 and 125 GeV for some parameter values in our model, which are consistent with CERN LEP2 data.

We report the first study of the glueball properties at finite temperatures below $T_c$ using SU(3) anisotropic lattice QCD with $\beta =6.25,$ the renormalized anisotropy $\xi \equiv a_s{/a}_t=4\mathrm{}$ and ${20}^3\times N_t{(N}_t=35,36,37,38,40,43,45,50,72)$ at the quenched level. From the temporal correlation analysis with the smearing method, about 20% mass reduction is observed for the lowest scalar glueball as $m_G\mathrm{}\left(T\right)=1250\mathrm{}\pm 50\hspace{0.5em}\mathrm{MeV}$ for ${0.8T}_c<T<\mathrm{}{T}_c$ in comparison with $m_G\simeq 1500–1700$ MeV at $T\simeq 0.$

We examine quenched chiral logarithms in lattice QCD with the overlap Dirac quark. For 100 gauge configurations generated with the Wilson gauge action at $\beta =5.8\mathrm{}$ on the $8^3\times 24$ lattice, we compute quenched quark propagators for 12 bare quark masses. The pion decay constant is extracted from the pion propagator, and from this the lattice spacing is determined to be 0.147 fm. The presence of a quenched chiral logarithm in the pion mass is confirmed, and its coefficient is determined to be $\delta =0.203\mathrm{}\pm 0.014,$ in agreement with the theoretical estimate in quenched chiral perturbation theory. Further, we obtain the topological susceptibility of these 100 gauge configurations by measuring the index of the overlap Dirac operator. Using a formula due to exact chiral symmetry, we obtain the ${\eta }^{\prime }$ mass in quenched chiral perturbation theory, $m_{{\eta }^{\prime }}=901\mathrm{}\pm 64\hspace{0.5em}\mathrm{MeV},$ and an estimate of $\delta =0.197\mathrm{}\pm 0.027,$ which is in good agreement with that determined from the pion mass.

We report on the lattice quark propagator using standard and improved staggered quark actions, with the standard Wilson gauge action. The standard Kogut-Susskind action has errors of $\mathcal{O}{(a}^2)$ while the “Asqtad” action has $\mathcal{O}{(a}^4),$ $\mathcal{O}{(a}^2{g}^2)$ errors. The quark propagator is interesting for studying the phenomenon of dynamical chiral symmetry breaking and as a testbed for improvement. Gauge dependent quantities from lattice simulations may be affected by Gribov copies. We explore this by studying the quark propagator in both Landau and Laplacian gauges. Landau and Laplacian gauges are found to produce very similar results for the quark propagator.

We find the renormalization coefficients of the quark field and the flavor nonsinglet fermion bilinear operators for the domain wall fermion action, in the regularization independent (RI) renormalization scheme. Our results are from a quenched simulation, on a ${16}^3\times 32$ lattice, with $\beta =6.0\mathrm{}$ and an extent in the fifth dimension of $16.$ We also discuss the expected effects of the residual chiral symmetry breaking inherent in a domain wall fermion simulation with a finite fifth dimension, and study the evidence for both explicit and spontaneous chiral symmetry breaking effects in our numerical results. We find that the relations between different renormalization factors predicted by chiral symmetry are, to a good approximation, satisfied by our results and that systematic effects due to the (low energy) spontaneous chiral symmetry breaking and zero modes can be controlled. Our results are compared against the perturbative predictions for both their absolute value and renormalization scale dependence.

We consider the standard model with an arbitrary number $n_H$ of Higgs doublets and enlarge the lepton sector by adding to each lepton family l a right-handed neutrino singlet ${\nu }_{\mathrm{lR}}.$ We assume that all the Yukawa-coupling matrices are diagonal, but the Majorana mass matrix $M_R$ of the right-handed neutrino singlets is an arbitrary symmetric matrix, thereby introducing an explicit but soft violation of all lepton numbers. We investigate lepton-flavor-violating processes within this model. We pay particular attention to the large-$m_R$ behavior of the amplitudes for these processes, where $m_R$ is the order of magnitude of the matrix elements of $M_R.$ While the amplitudes for processes such as ${\tau }^{-}\to {\mu }^{-}\gamma$ and $\overrightarrow{Z}{\tau }^{+}{\mu }^{-}$ drop as ${1/m}_R^2$ for arbitrary $n_H,$ processes such as ${\tau }^{-}\to {\mu }^{-}{e}^{+}{e}^{-}$ and ${\mu }^{-}\to e^{-}{e}^{+}{e}^{-}$ obey this power law only for $n_H=1.\mathrm{}$ For $n_H>~2,$ on the contrary, those amplitudes do not fall off when $m_R$ increases, rather they converge towards constants. This “nondecoupling” of the right-handed scale occurs because of the subprocess $l^{-}\to l^{\prime -}{S}_b^{0*},$ where $S_b^0$ is a neutral scalar which subsequently decays to $e^{+}{e}^{-}.$ That sub-process has a contribution from charged-scalar exchange which, for $n_H>~2,$ does not decrease when $m_R$ tends to infinity. We also perform a general study of the nondecoupling and argue that, at the one-loop level, after performing the limit $m_R\to \infty$ and after removing the ${\nu }_R$ from the Lagrangian, our model becomes a normal multi-Higgs-doublet standard model with loop-suppressed flavor-changing Yukawa couplings. Finally, we show that in our model the branching ratios of all lepton-flavor-changing processes are several orders of magnitude smaller than present experimental limits, if one makes the usual assumptions about the mass scales in the seesaw mechanism.

We study, within Ginzburg-Landau theory, the responses of three-flavor superfluid quark-gluon plasmas to external magnetic fields and rotation, in both the color-flavor locked and isoscalar color-antitriplet diquark phases near the critical temperature. Fields are incorporated in the gradient energy arising from long wavelength distortions of the condensate, via covariant derivatives to satisfy local gauge symmetries associated with color and electric charge. Magnetic vortex formation, in response to external magnetic fields, is possible only in the isoscalar phase; in the color-flavor locked phase, external magnetic fields are incompletely screened by the Meissner effect. On the other hand, rotation of the superfluid produces vortices in the color-flavor locked phase; in the isoscalar phase, it produces a London gluon-photon mixed field. We estimate the coherence and Meissner lengths and critical magnetic fields for the two phases.

The masses of octet baryons are calculated by the method of QCD sum rules. Using generalized interpolating fields, three independent sets of QCD sum rules are derived which allow the extraction of low-lying $N*$ states with spin-parity 1/2+, 1/2- and 3/2- in both the non-strange and strange channels. The predictive ability of the sum rules is examined by a Monte Carlo based analysis procedure in which the three phenomenological parameters (mass, coupling, threshold) are treated as free parameters simultaneously. Realistic uncertainties in these parameters are obtained by simultaneously exploring all uncertainties in the QCD input parameters. Those sum rules with good predictive power are identified and their predictions are compared with experiment where available.

The MiniBooNE detector at Fermilab is designed to search for ${\nu }_{\mu }\to {\nu }_e$ oscillation appearance at $E_{\nu }\sim 1\hspace{0.5em}\mathrm{GeV}$ and to make a decisive test of the LSND signal. The main detector (inside a veto shield) is a spherical volume containing 0.680 ktons of mineral oil. This inner volume, viewed by 1280 phototubes, is primarily a Čerenkov medium, as the scintillation yield is low. The entire detector is under a 3 m earth overburden. Though the detector is not optimized for low-energy (tens of MeV) events, and the cosmic-ray muon rate is high (10 kHz), we show that MiniBooNE can function as a useful supernova neutrino detector. Simple trigger-level cuts can greatly reduce the backgrounds due to cosmic-ray muons. For a canonical Galactic supernova at 10 kpc, about 190 supernova ${\overline{\nu }}_e+\overrightarrow{p}{e}^{+}+n$ events would be detected. By adding MiniBooNE to the international network of supernova detectors, the possibility of a supernova being missed would be reduced. Additionally, the paths of the supernova neutrinos through Earth will be different for MiniBooNE and other detectors, thus allowing tests of matter-affected mixing effects on the neutrino signal.

We present the prospects of searching for excited leptons during run II of the Fermilab Tevatron. We concentrate on single and pair production of excited electrons in the photonic decay channel for both $2\hspace{0.5em}{\mathrm{fb}}^{-1}$ (run IIa) and $15\hspace{0.5em}{\mathrm{fb}}^{-1}$ (run IIb) using one CDF or $\mathrm{D}\mathrm{Ø}$ detector equivalent. We expect the Tevatron to improve upon the limits set by CERN LEP and DESY HERA for excited lepton masses above 190 GeV by the end of run IIa.

We present the results of a search in $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{}\mathrm{TeV}$ for anomalous production of events containing a photon with large transverse energy and a lepton $(e$ or $\mu )$ with large transverse energy, using $86\hspace{0.5em}{\mathrm{pb}}^{-1}$ of data collected with the Collider Detector at Fermilab during the 1994–1995 collider run at the Fermilab Tevatron. The presence of large missing transverse energy $\left(E_T\right),$ additional photons, or additional leptons in these events is also analyzed. The results are consistent with standard model expectations, with the possible exception of photon-lepton events with large $E_T,$ for which the observed total is 16 events and the expected mean total is $7.6\pm 0.7$ events.