Using proton-proton collision data collected by the LHCb experiment at $\sqrt{s}=7\mathrm{TeV}$, corresponding to an integrated luminosity of $1.0{\mathrm{fb}}^{-1}$, the ratio of branching fractions of the $B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\pi }^{+}$ decay relative to the $B^0\to D^{*-}{\pi }^{+}$ decay is measured to be $\frac{\mathcal{B}(B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\pi }^{+})}{\mathcal{B}(B^0\to D^{*-}{\pi }^{+})}=2.64\pm 0.04(\mathrm{stat})\pm 0.13(\mathrm{syst})$. The Cabibbo-suppressed decay $B^0\to D^{*-}{K}^{+}{\pi }^{-}{\pi }^{+}$ is observed for the first time, and the measured ratio of branching fractions is $\frac{\mathcal{B}(B^0\to D^{*-}{K}^{+}{\pi }^{-}{\pi }^{+})}{\mathcal{B}(B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\pi }^{+})}=(6.47\pm 0.37(\mathrm{stat})\pm 0.35(\mathrm{syst}))\times {10}^{-2}$. A search for orbital excitations of charm mesons contributing to the $B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\pi }^{+}$ final state is also performed, and the first observation of the $B^0\to {\overline{D}}_1(2420{)}^0{\pi }^{+}{\pi }^{-}$ decay is reported with the ratio of branching fractions $\frac{\mathcal{B}(B^0\to ({\overline{D}}_1(2420{)}^0\to D^{*-}{\pi }^{+}){\pi }^{-}{\pi }^{+})}{\mathcal{B}(B^0\to D^{*-}{\pi }^{+}{\pi }^{-}{\pi }^{+})}=(2.04\pm 0.42(\mathrm{stat})\pm 0.22(\mathrm{syst}))\times {10}^{-2}$, where the numerator represents a product of the branching fractions $\mathcal{B}(B^0\to {\overline{D}}_1(2420{)}^0{\pi }^{-}{\pi }^{+})$ and $\mathcal{B}({\overline{D}}_1(2420{)}^0\to D^{*-}{\pi }^{+})$.

Using a matrix model, we model the deconfining phase transition at nonzero temperature for a $SU(N)$ gauge theory at large $N$. At infinite $N$ the matrix model exhibits a Gross-Witten-Wadia transition. We show that at the critical temperature $T_d$, both the order-disorder and the order-order interface tensions vanish identically. We estimate how these quantities approach zero in the matrix model as $T\to T_d$ and as $N\to \infty$. The numerical solution of the matrix model suggests possible nonmonotonic behavior in $N$ for relatively small values of $N$, $N\sim 5$.

It is possible to associate temperatures with the nonextremal horizons of a large class of spherically symmetric spacetimes using periodicity in the Euclidean sector, and this procedure works for the de Sitter spacetime as well. But unlike, e.g., the black hole spacetimes, the de Sitter spacetime also allows a description in Friedmann coordinates. This raises the question of whether the thermality of the de Sitter horizon can be obtained working entirely in the Friedmann coordinates, without reference to the static coordinates or using the symmetries of de Sitter spacetime. We discuss several aspects of this issue for de Sitter and approximately de Sitter spacetimes in the Friedmann coordinates (with a time-dependent background and the associated ambiguities in defining the vacuum states). The different choices for the vacuum states, the behavior of the mode functions and the detector response are studied in both ($1+1$) and ($1+3$) dimensions. We compare and contrast the differences brought about by the different choices. In the last part of the paper, we also describe a general procedure for studying quantum field theory in spacetimes which are approximately de Sitter and, as an example, derive the corrections to the thermal spectrum due to the presence of pressure-free matter.

Parameter estimation of binary black-hole merger events in gravitational-wave data relies on matched-filtering techniques which, in turn, depend on accurate model waveforms. Here we characterize the systematic biases introduced in measuring astrophysical parameters of binary black holes by applying the currently most accurate effective-one-body templates to simulated data containing nonspinning numerical-relativity waveforms. We quantify the systematic bias by using a Markov chain Monte Carlo algorithm to sample the posterior distribution function of noise-free data, and compare the offset of the maximum a priori waveform parameters (the bias) to the width of the distribution, which we refer to as the statistical error. For advanced ground-based detectors, we find that the systematic biases are well within the statistical error for realistic signal-to-noise ratios. These biases grow to be comparable to the statistical errors at high ground-based-instrument signal-to-noise ratios ($\mathrm{SNR}\sim 50$), but never dominate the error budget. At the much larger signal-to-noise ratios expected for space-based detectors, these biases will become large compared to the statistical errors, but for astrophysical black hole mass estimates the absolute biases (of at most a few percent) are still fairly small.

In the littlest Higgs model with $T$-parity, the production cross section of the $T$-odd heavy gauge boson pair $Z_H{W}_H$ is sizable at the LHC. In addition, both the $Z_H$ and $W_H$ bosons have almost exclusively one decay channel into $H{A}_H$ and $W{A}_H$, respectively, where the dark matter candidate $A_H$ yields a large missing transverse energy signal. Upon the discovery of the Higgs boson at 125 GeV, we study the discovery sensitivity of the final state $pp\to \ell b\overline{b}+{\mathrm{E̸}}_T$ to probe the model at the LHC. We find that the standard model backgrounds are manageable by applying suitable kinematic cuts. The LHC running at $\sqrt{s}=14\mathrm{TeV}$ with a $100{\mathrm{fb}}^{-1}$ total luminosity is sensitive to the model with the signal significance above 5 if the symmetry breaking scale $f$ is below about 850 GeV.

In this paper we make a systematic study of the semileptonic decays $B/B_s\to (\eta ,{\eta }^{\prime },G)(l^{+}{l}^{-},l\overline{\nu },\nu \overline{\nu })$ by employing the perturbative QCD (pQCD) factorization approach. The next-to-leading-order (NLO) contributions to the relevant form factors are included, and the ordinary $\eta \mathrm{\text{−}}{\eta }^{\prime }$ mixing scheme and the $\eta \mathrm{\text{−}}{\eta }^{\prime }\mathrm{\text{−}}G$ mixing scheme are considered separately, where $G$ denotes a pseudoscalar glueball. The numerical results and the phenomenological analysis indicate that (a) the NLO contributions to the relevant form factors provide 25% enhancement to the leading-order pQCD predictions for the branching ratios $\mathrm{Br}(B^{-}\to {\eta }^{{(}^{\prime })}{l}^{-}{\overline{\nu }}_l)$, leading to a good agreement between the predictions and the data; (b) for all considered decays, the pQCD results are basically consistent with those from other different theoretical models; (c) the pQCD predictions in the two considered mixing schemes agree well with each other within theoretical errors. The outcomes presented here can be tested by LHCb and forthcoming Super-$B$ experiments.

We show that charged vector mesons cannot be condensed by a magnetic field. Although some hadron models predict the charged vector meson condensation in a strong magnetic field, we prove, by means of the Vafa-Witten theorem, that this is not the case in QCD. We also perform the numerical analysis for the meson mass and condensation in lattice QCD. The lattice QCD data confirm no charged vector meson condensation in a magnetic field.

We apply the relative weights method [J. Greensite, Phys. Rev. D 86, 114507 (2012)] to determine the effective Polyakov line action for SU(2) lattice gauge theory in the confined phase, at lattice coupling $\beta =2.2$ and $N_t=4$ lattice spacings in the time direction. The effective action turns out to be bilinear in the fundamental representation Polyakov line variables, with a rather simple expression for the finite range kernel. The validity of this action is tested by computing Polyakov line correlators, via Monte Carlo simulation, in both the effective action and the underlying lattice theory. It is found that the correlators in each theory are in very close agreement.

The strong decays of $\Xi$ baryons up to $N=2$ shell are studied in a chiral quark model. The strong decay properties of these well-established ground decuplet baryons are reasonably described. We find that (i) $\Xi (1690)$ and $\Xi (1820)$ could be assigned to the spin-parity $J^P=1/2^{-}$ state $|70,{}^{2}8,1,1,\frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{}⟩$ and the spin-parity $J^P=3/2^{-}$ state $|70,{}^{2}8,1,1,\frac{3}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{}⟩$, respectively. Slight configuration mixing might exist in these two negative parity states. (ii) $\Xi (1950)$ might correspond to several different $\Xi$ resonances. The broad states ($\Gamma \sim 100\mathrm{MeV}$) observed in the $\Xi \pi$ channel could be classified as the pure $J^P=5/2^{-}$ octet state $|70,{}^{4}8,1,1,\frac{5}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{}⟩$ or the mixed state $|\Xi \frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{}{⟩}_3$ with $J^P=1/2^{-}$. The $\Xi$ resonances with moderate width ($\Gamma \sim 60\mathrm{MeV}$) observed in the $\Xi \pi$ channel might correspond to the $J^P=1/2^{+}$ excitation $|56,{}^{4}10,2,2,\frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{+}}{}⟩$. The second orbital excitation $|56,{}^{4}10,2,2,\frac{3}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{+}}{}⟩$ and the mixed state $|\Xi \frac{1}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{-}}{}{⟩}_1$ might be candidates for the narrow width state observed in the $\Lambda \overline{K}$ channel; however, their spin-parity numbers are incompatible with the moment analysis of the data. (iii) $\Xi (2030)$ could not be assigned to either any spin-parity $J^P=7/2^{+}$ states or any pure $J^P=5/2^{+}$ configurations. It seems to favor the $|70,{}^{2}8,2,2,\frac{3}{2}\genfrac{}{}{0ex}{}{{\mathrm{}}^{+}}{}⟩$ assignment; however, its spin conflicts with the moment analysis of the data. To find more $\Xi$ resonances, the observations in the $\Xi (1530)\pi$ and $\Sigma (1385)\overline{K}$ channels are necessary.

The far site detector complex of the Daya Bay reactor experiment is proposed as a location to search for sterile neutrinos with $\ge \mathrm{eV}$ mass. Antineutrinos from a 500 kCi ${}^{144}\mathrm{Ce}\mathrm{\text{−}}{}^{144}\mathrm{Pr}$ $\beta$-decay source ($\Delta Q=2.996\mathrm{MeV}$) would be detected by four identical 20-ton antineutrino targets. The site layout allows flexible source placement; several specific source locations are discussed. In one year, the $3+1$ sterile neutrino hypothesis can be tested at essentially the full suggested range of the parameters $\Delta m_{\mathrm{new}}^2$ and ${sin}^{2}2{\theta }_{\mathrm{new}}$ (90% C.L.). The backgrounds from six nuclear reactors at $\ge 1.6\mathrm{km}$ distance are shown to be manageable. Advantages of performing the experiment at the Daya Bay far site are described.

We show that weak scale vectorlike fermions with order one couplings to the Higgs can lead to a novel mechanism for a strongly first-order electroweak phase transition through their tendency to drive the Higgs quartic coupling negative. These same fermions could also enhance the loop-induced branching fraction of the Higgs into two photons, as suggested by the recent discovery of a $\sim 125\mathrm{GeV}$ Higgs-like state at the CERN LHC. Our results suggest that measurements of the diphoton decay rate of the Higgs and its self-coupling, at the LHC or perhaps at a future lepton collider, could probe the electroweak phase transition in the early Universe, with significant implications for the viability of electroweak baryogenesis scenarios.

We discuss the thermodynamics of the $O(N)$ model across the corresponding phase transition using the two-loop $\Phi$-derivable approximation of the effective potential and compare our results to those obtained in the literature within the Hartree-Fock approximation. In particular, we find that in the chiral limit the transition is of the second order, whereas it was found to be of the first order in the Hartree-Fock case. These features are manifest at the level of the thermodynamical observables. We also compute the thermal sigma and pion masses from the curvature of the effective potential. In the chiral limit, this guarantees that Goldstone’s theorem is obeyed in the broken phase. A realistic parametrization of the model in the $N=4$ case, based on the vacuum values of the curvature masses, shows that a sigma mass of around 450 MeV can be obtained. The equations are renormalized after extending our previous results for the $N=1$ case by means of the general procedure described in Ref. [8]. When restricted to the Hartree-Fock approximation, our approach reveals that certain problems raised in the literature concerning the renormalization are completely lifted. Finally, we introduce a new type of $\Phi$-derivable approximation in which the gap equation is not solved at the same level of accuracy as the accuracy at which the potential is computed. We discuss the consistency and applicability of these types of “hybrid” approximations and illustrate them in the two-loop case by showing that the corresponding effective potential is renormalizable and that the transition remains of the second order.

The quasistatic solutions of the matter density perturbation in $F(R)$ gravity models have been investigated in numerous papers. However, the oscillating solutions in $F(R)$ gravity models have not been investigated enough so far. In this paper, the oscillating solutions are also examined by using appropriate approximations. And the behaviors of the matter density perturbation in $F(R)$ gravity models with singular evolutions of the physical parameters are shortly investigated as applications of the approximated calculations.

In this paper, considering the probe limit, we analytically study the onset of holographic $s$-wave condensate in the planar Schwarzschild-AdS background. Inspired by various low-energy features of string theory, in the present work we replace the conventional Maxwell action with a (nonlinear) Born-Infeld action which essentially corresponds to the higher-derivative corrections of the gauge fields. Based on a variational method which is commonly known as the Sturm-Liouville eigenvalue problem and considering a nontrivial asymptotic solution for the scalar field, we compute the critical temperature for the $s$-wave condensation. The results thus obtained analytically agree well with the numerical findings [J. Jing and S. Chen, Phys. Lett. B 686, 68 (2010)]. As a next step, we extend our perturbative technique to compute the order parameter for the condensation. Interestingly, our analytic results are found to be of the same order as the numerical values obtained earlier.

The Higgs-dilaton cosmological model is able to describe simultaneously an inflationary expansion in the early Universe and a dark energy dominated stage responsible for the present day acceleration. It also leads to a nontrivial relation between the spectral tilt of scalar perturbations $n_s$ and the dark energy equation of state $\omega$. We study the self-consistency of this model from an effective field theory point of view. Taking into account the influence of the dynamical background fields, we determine the effective cutoff of the theory, which turns out to be parametrically larger than all the relevant energy scales from inflation to the present epoch. We finally formulate the set of assumptions needed to estimate the amplitude of the quantum corrections in a systematic way and show that the connection between $n_s$ and $\omega$ remains unaltered if these assumptions are satisfied.

We present our results on meson and nucleon screening masses in finite temperature two flavor QCD using smeared staggered valence quarks and staggered thin-link sea quarks with different lattice spacings and quark masses. We investigate optimization of smearing by observing its effects on the IR and UV components of gluon and quark fields. The application of smearing to screening at finite temperature also provides a transparent window into the mechanism of the interplay of smearing and chiral symmetry. The improved hadronic operators show that for temperature $T\ge 1.5T_c$ ($T_c$ is the finite temperature cross over), screening masses are consistent with weak-coupling predictions. There is also evidence for a rapid opening up of a spectral gap of the Dirac operator immediately above $T_c$.

Using the primordial helium abundance, an upper limit to the magnetic moments for Dirac neutrinos had been provided by imposing restrictions on the number of the additional helicity states. Considering nonthermal photons produced in the decay of the heavy sterile mass eigenstates due to the neutrino magnetic moment, we explore the constraints imposed by the observed abundances of all the light elements produced during the big-bang nucleosynthesis.

We derive an exact unified formula for all condensates (quark and monopole) in the hybrid $r$ vacua in $\mathcal{N}=2$ supersymmetric QCD slightly deformed by a $\mu {\mathcal{A}}^2$ term. The gauge group is assumed to be $\mathrm{U}(N)$ and the number of the quark flavors $N_f$ subject to the condition $N<N_f<2N$. In the $r$ vacua, $r$ quarks and $N-r-1$ monopoles from nonoverlapping subgroups of $\mathrm{U}(N)$ develop vacuum expectation values ($r<N$). We then briefly review possible dynamical regimes (confinement, screening, and “instead of confinement”) in the hybrid $r$ vacua in $\mu$-deformed $\mathcal{N}=2$ supersymmetric QCD (the small-$\mu$ limit).

Explicit solutions for extended objects of a $Q$-ball type were found analytically in a model describing complex scalar field with piecewise parabolic potential in ($3+1$)- and ($1+1$)-dimensional space-times. Such a potential provides a variety of solutions which were thoroughly examined. It was shown that, depending on the values of the parameters of the model and according to the known stability criteria, there exist stable and unstable solutions. The classical stability of solutions in ($1+1$)-dimensional space-time was examined in the linear approximation and it was shown explicitly that the spectrum of linear perturbations around some solutions contains exponentially growing modes while it is not so for other solutions.

We calculate the explicit equations of motion for nonspinning compact objects to 2.5 post-Newtonian order, or $O(v/c{)}^5$ beyond Newtonian gravity, in a general class of scalar-tensor theories of gravity. We use the formalism of the direct integration of the relaxed Einstein equations (DIRE), adapted to scalar-tensor theory, coupled with an approach pioneered by Eardley for incorporating the internal gravity of compact, self-gravitating bodies. For the conservative part of the motion, we obtain the two-body Lagrangian and conserved energy and momentum through second post-Newtonian order. We find the 1.5 post-Newtonian and 2.5 post-Newtonian contributions to gravitational radiation reaction, the former corresponding to the effects of dipole gravitational radiation, and verify that the resulting energy loss agrees with earlier calculations of the energy flux. For binary black holes we show that the motion through 2.5 post-Newtonian order is observationally identical to that predicted by general relativity. For mixed black-hole neutron-star binary systems, the motion is identical to that in general relativity through the first post-Newtonian order but deviates from general relativity beginning at 1.5 post-Newtonian order, in part through the onset of dipole gravitational radiation. But through 2.5 post-Newtonian order, those deviations in the motion of a mixed system are governed by a single parameter, dependent only upon the coupling constant ${\omega }_0$ and the structure of the neutron star, and are formally the same for a general class of scalar-tensor theories as they are for pure Brans-Dicke theory.