We propose a new pattern of the neutrino mixing matrix which can be parametrized as the product of an arbitrary Hermitian matrix and the well-known tribimaximal mixing matrix. In this scenario, nontrivial values of the smallest neutrino mixing angle ${\theta }_{13}$ and the $CP$-violating phases entirely arise from the nonunitary corrections. We present a complete set of series expansion formulas for neutrino oscillation probabilities both in vacuum and in matter of constant density. We do a numerical analysis to show the nonunitary effects on neutrino oscillations. The possibility of determining small nonunitary perturbations and $CP$-violating phases is discussed by measuring neutrino oscillation probabilities and constructing “deformed unitarity triangles.” Some brief comments on the nonunitary neutrino mixing matrix in the type-II seesaw models are also given.

The Large Hadron Collider program will include the identification of events with single prompt high-$k_{\perp }$ photons as probes of new physics. We show that this channel is uniquely suited to search for experimental evidence of TeV-scale open string theory. At the parton level, we analyze single photon production in gluon fusion, $gg\to \gamma g$, with open string states propagating in intermediate channels. If the photon mixes with the gauge boson of the baryon number, which is a common feature of D-brane quivers, the amplitude appears already at the string disk level. It is completely determined by the mixing parameter (which is actually determined in the minimal theory)—and it is otherwise model-(compactification-) independent. We discuss the string signal cross sections as well as the QCD background. The present analysis takes into account the recently obtained decay widths of first Regge recurrences, which are necessary for more precise determination of these cross sections in the resonant region. A vital part of the background discussion concerns the minimization of misidentified ${\pi }^0$’s emerging from high-$p_{\perp }$ jets. We show that even for relatively small mixing, $100{\mathrm{fb}}^{-1}$ of Large Hadron Collider data could probe deviations from standard model physics associated with TeV-scale strings at a $5\sigma$ significance, for $M_{\mathrm{string}}$ as large as 2.3 TeV. It is also likely that resonant bumps could be observed with approximately the same signal-to-noise ratio.

We discuss fermion masses and mixings in models derived from orbifold grand unified theories such that gauge coupling unification is achieved without low-energy supersymmetry by utilizing a noncanonical $U(1{)}_Y$. A gauged $U(1{)}_X$ flavor symmetry plays an essential role, and the Green-Schwarz mechanism is invoked in anomaly cancellations. Models containing vectorlike particles with masses close to $M_{\mathrm{GUT}}$ are also discussed.

We investigate charged tracks signals of a supersymmetric scenario, where the lighter stop is the next-to-lightest supersymmetric particle. It is found that such a next-to-lightest supersymmetric particle is stable on the scale of the detector at the CERN LHC if one has a right-chiral sneutrino as the lightest supersymmetric particle. After identifying some benchmark points in the parameter space of a supergravity scenario with nonuniversal scalar masses, we study a few specific classes of signals, namely, stop pair production and gluino pair production followed by each decaying into a stop and a top. It is shown that proper kinematic cuts remove the backgrounds in each case, and an integrated luminosity of even $1{\mathrm{fb}}^{-1}$ is likely to yield copious events of the first kind, while a larger luminosity may be required for the other type. One can also aspire to reconstruct the gluino mass, using the “visible” stable next-to-lightest supersymmetric particle tracks.

We study the production of the charged Higgs boson at the CERN LHC in the left-right symmetric model. It is shown that there exists a lower bound of the cross section. We investigate that predicted cross sections of this model are generally larger than those of the two Higgs doublet model or the minimal supersymmetric model.

This paper reports the results of a study of the supersymmetric neutral heavy Higgs boson production process $e^{+}{e}^{-}\to H^0{A}^0$ at $\sqrt{s}=1\mathrm{TeV}$ performed using fully simulated and reconstructed events. The adopted parameters for the supersymmetric models are compatible with the relic dark matter density if this is due to neutralinos annihilating through the $A^0$ boson in the early universe. The accuracies on the heavy Higgs boson masses, widths, and decay branching fractions are estimated to be $\delta M_{A^0}/M_{A^0}=0.0024$ $\delta {\Gamma }_{A^0}/{\Gamma }_{A^0}=0.19$, $\delta \mathrm{BR}(A^0\to b\overline{b})/\mathrm{BR}(A^0\to b\overline{b})=0.07$, and $\delta \mathrm{BR}(A^0\to {\tau }^{+}{\tau }^{-})/\mathrm{BR}(A^0\to {\tau }^{+}{\tau }^{-})=0.15$ These results, combined with other measurements from the LHC and an $e^{+}{e}^{-}$ collider, allow the supersymmetric dark matter density to be inferred to a relative accuracy $\delta {\Omega }_{\chi }{h}^2/{\Omega }_{\chi }{h}^2=0.08$.

We propose to perform fully dynamical simulations at small quark masses by reweighting in the quark mass. This approach avoids some of the technical difficulties associated with direct simulations at very small quark masses. We calculate the weight factors stochastically, using determinant breakup and low mode projection to reduce the statistical fluctuations. We find that the weight factors fluctuate only moderately on nHYP smeared dynamical Wilson-clover ensembles, and we could successfully reweight ${16}^4$, $(1.85\mathrm{fm}{)}^4$ volume configurations from $m_q\approx 20\mathrm{MeV}$ to $m_q\approx 5\mathrm{MeV}$ quark masses, reaching the $ϵ$-regime. We illustrate the strength of the method by calculating the low energy constant $F$ from the $ϵ$-regime pseudoscalar correlator.

We calculate the ghost two-point function in Coulomb gauge QCD with a simple model vacuum gluon wave function using Monte Carlo integration. This approach extends the previous analytic studies of the ghost propagator with this ansatz, where a ladder-rainbow expansion was unavoidable for calculating the path integral over gluon field configurations. The new approach allows us to study the possible critical behavior of the coupling constant, as well as the Coulomb potential derived from the ghost dressing function. We demonstrate that IR enhancement of the ghost correlator or Coulomb form factor fails to quantitatively reproduce confinement using Gaussian vacuum wave functional.

A combined fit is performed to the BABAR and Belle measurements of the $e^{+}{e}^{-}\to {\pi }^{+}{\pi }^{-}\psi (2S)$ cross sections for center-of-mass energy between threshold and 5.5 GeV. The resonant parameters of the $Y(4360)$ and $Y(4660)$ are determined. The mass is ${4355}_{-10}^{+9}\pm 9\mathrm{MeV}/c^2$ and the width is ${103}_{-15}^{+17}\pm 11\mathrm{MeV}/c^2$ for the $Y(4360)$, and the mass is ${4661}_{-8}^{+9}\pm 6\mathrm{MeV}/c^2$ and the width is ${42}_{-12}^{+17}\pm 6\mathrm{MeV}/c^2$ for the $Y(4660)$. The production of the $Y(4260)$ in ${\pi }^{+}{\pi }^{-}\psi (2S)$ mode is found to be at $2\sigma$ level, and $\mathcal{B}(Y(4260)\to {\pi }^{+}{\pi }^{-}\psi (2S))·{\Gamma }_{e^{+}{e}^{-}}$ is found to be less than $4.3\mathrm{eV}/c^2$ at the 90% confidence level, or equal to ${7.4}_{-1.7}^{+2.1}\mathrm{eV}/c^2$ depending on whether it interferes with the $Y(4360)$ constructively or destructively. This information will shed light on the understanding of the nature of the $Y$ states observed in initial state radiation processes.

We calculate absorptive corrections to single pion exchange in the production of leading neutrons in $pp$ collisions. Contrary to the usual procedure of convolving the survival probability with the cross section, we apply corrections to the spin amplitudes. The nonflip amplitude turns out to be much more suppressed by absorption than the spin-flip one. We identify the projectile proton Fock state responsible for the absorptive corrections as a color octet-octet 5-quarks configuration. Calculations within two very different models, color-dipole light-cone description, and in hadronic representation, lead to rather similar absorptive corrections. We found a much stronger damping of leading neutrons than in some of previous estimates. Correspondingly, the cross section is considerably smaller than was measured at ISR. However, comparison with recent measurements by the ZEUS collaboration of neutron production in deep-inelastic scattering provides a strong motivation for challenging the normalization of the ISR data. This conjecture is also supported by preliminary data from the NA49 experiment for neutron production in $pp$ collisions at SPS.

We study relativistic Bose-Einstein condensation at finite density and temperature using the linear sigma model in the one-particle-irreducible $1/N$ expansion. We derive the effective potential to next-to-leading (NLO) order and show that it can be renormalized in a temperature-independent manner. As a particular application, we study the thermodynamics of the pion gas in the chiral limit as well as with explicit symmetry breaking. At nonzero temperature we solve the NLO gap equation and show that the results describe the chiral-symmetry-restoring second-order phase transition in agreement with general universality arguments. However, due to nontrivial regularization issues, we are not able to extend the NLO analysis to nonzero chemical potential.

We carry out a systematic study of the heavy-light meson strong decays in a chiral quark model. For the $S$-wave vectors [$D^{*}(2007)$, $D^{*\pm }(2010)$], $P$-wave scalars [$D_0^{*}(2400)$, $B_0^{*}(5730)$], and tensors [$D_2^{*}(2460)$, $D_{s2}^{*}(2573)$], we obtain results in good agreement with the experimental data. For the axial vectors $D_1(2420)$ and $D_1^{\prime }(2430)$, a state mixing scheme between $1{}^{1}P_1$ and $1{}^{3}P_1$ is favored with a mixing angle $\varphi \simeq -(55\pm 5)°$, which is consistent with previous theoretical predictions. The same mixing scheme also applies to $D_{s1}(2460)$ and $D_{s1}(2536)$ that accounts for the narrow width of the $D_{s1}(2536)$ and its dominant decay into $D^{*}K$. For $B_1(5725)$ and $B_1^{\prime }(5732)$, such a mixing explains well the decay width of the former but leads to an even broader $B_1^{\prime }(5732)$. Predictions for the strange-bottom axial vectors are also made. For the undetermined meson $D^{*}(2640)$, we find that they fit well in the radially excited state $2{}^{3}S_1$ according to its decay mode. The newly observed $D_{sJ}^{*}(2860)$ strongly favors the $D$-wave excited state $1{}^{3}D_3$. For $D_{sJ}^{*}(2632)$ and $D_{sJ}^{*}(2690)$, we find they are difficult to fit in any $D_s$ excitations in that mass region, if the experimental data are accurate. Theoretical predictions for decay modes of those unobserved states as multiplets of $2S$ and $1D$ waves are also presented, which should be useful for the further experimental search for those states.

Many of the proposed solutions to the hierarchy and naturalness problems postulate new “partner” fields to the standard model particles. Determining the spins of these new particles will be critical in distinguishing among the various possible standard model extensions, yet proposed methods rely on the underlying models. We propose a new model-independent method for spin measurements which takes advantage of quantum interference among helicity states. We demonstrate that this method will be able to discriminate scalar particles from higher spin states at a linear collider.

We study production and equilibration of pions and muons in relativistic electron-positron-photon plasma at a temperature of $T\ll m_{\mu }$, $m_{\pi }$. We argue that the observation of pions and muons can be a diagnostic tool in the study of the initial properties of such a plasma formed by means of strong laser fields. Conversely, properties of muons and pions in a thermal environment become accessible to precise experimental study.

We show the first lattice QCD results on the axial charge $g_A^{N^{*}{N}^{*}}$ of $N^{*}(1535)$ and $N^{*}(1650)$. The measurements are performed with two flavors of dynamical quarks employing the renormalization-group improved gauge action at $\beta =1.95$ and the mean-field improved clover quark action with the hopping parameters, $\kappa =0.1375$, 0.1390, and 0.1400. In order to properly separate signals of $N^{*}(1535)$ and $N^{*}(1650)$, we construct $2\times 2$ correlation matrices and diagonalize them. Wraparound contributions in the correlator, which can be another source of signal contaminations, are eliminated by imposing the Dirichlet boundary condition in the temporal direction. We find that the axial charge of $N^{*}(1535)$ takes small values such as $g_A^{N^{*}{N}^{*}}\sim \mathcal{O}(0.1)$, whereas that of $N^{*}(1650)$ is about 0.5, which is found independent of quark masses and consistent with the predictions by the naive nonrelativistic quark model.

We present a simple formalism for parton-shower Markov chains. As a first step towards more complete “uncertainty bands,” we incorporate a comprehensive exploration of the ambiguities inherent in such calculations. To reduce this uncertainty, we then introduce a matching formalism which allows a generated event sample to simultaneously reproduce any infrared-safe distribution calculated at leading or next-to-leading order in perturbation theory, up to subleading corrections. To enable a more universal definition of perturbative calculations, we also propose a more general definition of the hadronization cutoff. Finally, we present an implementation of some of these ideas for final-state gluon showers, in a code dubbed Vincia.

We exploit the quantum coherence between pair-produced $D^0$ and ${\overline{D}}^0$ in $\psi (3770)$ decays to study charm mixing, which is characterized by the parameters $x$ and $y$, and to make a first determination of the relative strong phase $\delta$ between doubly Cabibbo-suppressed $D^0\to K^{+}{\pi }^{-}$ and Cabibbo-favored ${\overline{D}}^0\to K^{+}{\pi }^{-}$. We analyze a sample of $1.0\times {10}^6$ $D^0{\overline{D}}^0$ pairs from $281{\mathrm{pb}}^{-1}$ of $e^{+}{e}^{-}$ collision data collected with the CLEO-c detector at $E_{\mathrm{cm}}=3.77\mathrm{GeV}$. By combining CLEO-c measurements with branching fraction input and time-integrated measurements of $R_{\mathrm{M}}\equiv (x^2+y^2)/2$ and $R_{\mathrm{WS}}\equiv \Gamma (D^0\to K^{+}{\pi }^{-})/\Gamma ({\overline{D}}^0\to K^{+}{\pi }^{-})$ from other experiments, we find $\cos \delta ={1.03}_{-0.17}^{+0.31}\pm 0.06$, where the uncertainties are statistical and systematic, respectively. In addition, by further including external measurements of charm mixing parameters, we obtain an alternate measurement of $\cos \delta =1.10\pm 0.35\pm 0.07$, as well as $x\sin \delta =({4.4}_{-1.8}^{+2.7}\pm 2.9)\times {10}^{-3}$ and $\delta =({22}_{-12-11}^{+11+9})°$.

A $1\sigma$ range, $20°<{\Phi }_{3/2}<115°$, defining the slope of a linear Cabibbo-Kobayashi-Maskawa relation, $\overline{\eta }=\tan {\Phi }_{3/2}(\overline{\rho }-0.24\pm 0.03)$, was obtained from $B^0\to K^{*}\pi$ amplitudes measured in two Dalitz plot analyses of $B^0\to K\pi \pi$. A correction reported recently by the BABAR Collaboration in results for $B^0\to K^{+}{\pi }^{-}{\pi }^0$ is shown to imply a somewhat narrower $1\sigma$ range for the slope parameter, $39°<{\Phi }_{3/2}<112°$.

Present and planned dark matter detection experiments search for WIMP-induced nuclear recoils in poorly known background conditions. In this environment, the maximum gap statistical method provides a way of setting more sensitive cross section upper limits by incorporating known signal information. We give a recipe for the numerical calculation of upper limits for planned directional dark matter detection experiments, that will measure both recoil energy and angle, based on the gaps between events in two-dimensional phase space.

We present a realistic supersymmetric $SU(5)$ model combined with a nonanomalous $U(1{)}_F$ symmetry. We find a set of $U(1{)}_F$ charges which automatically lead to the realistic mass hierarchy and mixing patterns for quarks, leptons, and neutrinos. All gauge anomalies, including the $[U(1{)}_F{]}^3$ anomaly, are canceled in our model without invoking the Green-Schwarz mechanism or having exotic fields. Proton decay mediated by dimension-5 operators is automatically suppressed in our model, because the scale set by the largest right-handed neutrino mass is much less than the GUT scale.