We analyze neutral Higgs boson decays into squark pairs in the minimal supersymmetric extension of the standard model and improve previous analyses. In particular the treatment of potentially large higher-order corrections originating from the soft supersymmetry-breaking parameters $A_b$, the trilinear Higgs coupling to sbottoms, and $\mu$, the Higgsino mass parameter, is investigated. The remaining theoretical uncertainties including the supersymmetric QCD corrections are analyzed quantitatively.

The one-boson exchange potential model for ${\Lambda }_{c}N$ is constructed and the possibility of ${\Lambda }_{c}N$ bound states is examined. We consider an effective Lagrangian for the charmed baryons, ${\Lambda }_c$, ${\Sigma }_c$, and ${\Sigma }_c^{*}$, reflecting the heavy quark symmetry, chiral symmetry, and hidden local symmetry. We determine the coupling constants using various methods. With the derived nonrelativistic potentials, we study the bound state problem of the ${\Lambda }_{c}N$ system and relevant coupled channel effects. It is found that molecular bound states of ${\Lambda }_{c}N$ are plausible, for which the channel couplings of ${\Sigma }_{c}N$ and ${\Sigma }_c^{*}N$ are essential.

We calculate the branching ratios of the yet unmeasured ${\eta }^{\prime }$ decays into four pions, based on a combination of chiral perturbation theory and vector-meson dominance. The decays ${\eta }^{\prime }\to 2({\pi }^{+}{\pi }^{-})$ and ${\eta }^{\prime }\to {\pi }^{+}{\pi }^{-}2{\pi }^0$ are P-wave dominated and can largely be thought to proceed via two $\rho$ resonances; we predict branching fractions of $(1.0\pm 0.3)\times {10}^{-4}$ and $(2.4\pm 0.7)\times {10}^{-4}$, respectively, not much lower than the current experimental upper limits. The decays ${\eta }^{\prime }\to 4{\pi }^0$ and $\eta \to 4{\pi }^0$, in contrast, are D-wave driven as long as conservation of $CP$ symmetry is assumed, and are significantly further suppressed; any experimental evidence for the decay $\eta \to 4{\pi }^0$ could almost certainly be interpreted as a signal of $CP$ violation. We also calculate the $CP$-violating amplitudes for ${\eta }^{\prime }\to 4{\pi }^0$ and $\eta \to 4{\pi }^0$ induced by the QCD $\theta$-term.

We present a complete formalism for final-state (timelike) dipole-antenna showers including fermion masses, but neglecting polarization and finite-width effects. We make several comparisons of tree-level expansions of this shower algorithm to fixed-order matrix elements for hadronic $Z$ decays, up to and including $Z\to 6$ partons, to which the algorithm can be consistently matched over all of phase space. We also compare to analytical resummations at the next-to-leading logarithmic (NLL) level. The shower algorithm has been implemented in the publicly available VINCIA plug-in to the PYTHIA 8 event generator, which enables us to compare to experimental data at the fully hadronized level. We therefore also include comparisons to selected observables in $b$-tagged $Z$ decays.

We present a search for semileptonic $B$ decays to the charmed baryon ${\Lambda }_c^{+}$ based on $420{\mathrm{fb}}^{-1}$ of data collected at the ${\rm Y}(4S)$ resonance with the BABAR detector at the PEP-II $e^{+}{e}^{-}$ storage rings. By fully reconstructing the recoiling $B$ in a hadronic decay mode, we reduce non-$B$ backgrounds and determine the flavor of the signal $B$. We statistically correct the flavor for the effect of the $B^0$ mixing. We obtain a 90% confidence level upper limit of $\mathcal{B}(\overline{B}\to {\Lambda }_c^{+}X{\ell }^{-}{\overline{\nu }}_{\ell })/\mathcal{B}(\overline{B}\to {\Lambda }_c^{+}X)<3.5\%$.

I discuss a correspondence between string theory and the black hole membrane paradigm in the context of the D1-D5-P system. By using the Kubo formula, I calculate transport coefficients of the effective string model induced by two kinds of minimal scalars. Then, I show that these transport coefficients exactly agree with the corresponding membrane transport coefficients of a five-dimensional near-extremal black hole with three charges.

In this work, we probe the stability of a $z=3$ three-dimensional Lifshitz black hole by using scalar and spinorial perturbations. We found an analytical expression for the quasinormal frequencies of the scalar probe field, which perfectly agree with the behavior of the quasinormal modes obtained numerically. The results for the numerical analysis of the spinorial perturbations reinforce the conclusion of the scalar analysis, i.e., the model is stable under scalar and spinor perturbations. As an application we found the area spectrum of the Lifshitz black hole, which turns out to be equally spaced.

We recently developed a new general relativistic magnetohydrodynamic code with adaptive mesh refinement that evolves the electromagnetic (EM) vector potential $A_i$ instead of the magnetic fields directly. Evolving $A_i$ enables one to use any interpolation scheme on refinement level boundaries and still guarantee that the magnetic field remains divergenceless. As in classical EM, a gauge choice must be made when evolving $A_i$, and we chose a straightforward “algebraic” gauge condition to simplify the $A_i$ evolution equation. However, magnetized black hole–neutron star (BHNS) simulations in this gauge exhibit unphysical behavior, including the spurious appearance of strong magnetic fields on refinement level boundaries. This spurious behavior is exacerbated when matter crosses refinement boundaries during tidal disruption of the neutron star. Applying Kreiss-Oliger dissipation to the evolution of the magnetic vector potential $A_i$ slightly weakens this spurious magnetic effect, but with undesired consequences. We demonstrate via an eigenvalue analysis and a numerical study that zero-speed modes in the algebraic gauge, coupled with the frequency filtering that occurs on refinement level boundaries, are responsible for the creation of spurious magnetic fields. We show that the EM Lorenz gauge exhibits no zero-speed modes, and as a consequence, spurious magnetic effects are quickly propagated away, allowing for long-term, stable magnetized BHNS evolutions. Our study demonstrates how the EM gauge degree of freedom can be chosen to one’s advantage, and that for magnetized BHNS simulations the Lorenz gauge constitutes a major improvement over the algebraic gauge.

In this work we explore the consequences that a nonminimal coupling between geometry and matter can have on the dynamics of perfect fluids. It is argued that the presence of a static, axially symmetric pressureless fluid does not imply a Minkowski space-time like as is in general relativity. This feature can be attributed to a pressure mimicking mechanism related to the nonminimal coupling. The case of a spherically symmetric black hole surrounded by fluid matter is analyzed, and it is shown that under equilibrium conditions the total fluid mass is about twice that of the black hole. Finally, a generalization of the Newtonian potential for a fluid element is proposed and its implications are briefly discussed.

In this article we study the quantization and causal properties of a massive spin $3/2$ Rarita-Schwinger field on spatially flat Friedmann-Robertson-Walker (FRW) spacetimes. We construct Zuckerman’s universal conserved current and prove that it leads to a positive definite inner product on solutions of the field equation. Based on this inner product, we quantize the Rarita-Schwinger field in terms of a CAR-algebra. The transversal and longitudinal parts constituting the independent on-shell degrees of freedom decouple. We find a Dirac-type equation for the transversal polarizations, ensuring a causal propagation. The equation of motion for the longitudinal part is also of Dirac-type, but with respect to an “effective metric”. We obtain that for all four-dimensional FRW solutions with a matter equation of state $p=\omega \rho$ and $\omega \in (-1,1]$ the light cones of the effective metric are more narrow than the standard cones, which are recovered for the de Sitter case $\omega =-1$. In particular, this shows that the propagation of the longitudinal part, although nonstandard for $\omega \ne -1$, is completely causal in cosmological constant, dust and radiation dominated universes.

The nucleation process of quark matter in both cold and hot dense hadronic matter is investigated using a chiral approach to describe the quark phase. We use the Nambu–Jona–Lasinio and the chromo dielectric models to describe the deconfined phase and the nonlinear Walecka model for the hadronic one. The effect of hyperons on the transition phase between hadronic and quark matter is studied. The consequences of the nucleation process for neutron star physics are outlined.

Different experiments on hadron spectroscopy have long suspected the existence of several cascade states in the 1900–2000 MeV region. They are usually labeled under the common name of $\Xi (1950)$. As we argue here, there are also theoretical reasons supporting the idea of several $\Xi (1950)$ resonances. In particular, we propose the existence of three $\Xi (1950)$ states: one of these states would be part of a spin-parity ${\frac{1}{2}}^{-}$ decuplet and the other two probably would belong to the ${\frac{5}{2}}^{+}$ and ${\frac{5}{2}}^{-}$ octets. We also identify which decay channels are more appropriate for the detection of each of the previous states.

We study the semileptonic $b\to c$ decays of the lowest-lying triply heavy baryons made from $b$ and $c$ quarks in the limit $m_b$, $m_c\gg {\Lambda }_{\mathrm{QCD}}$ and close to the zero-recoil point. The separate heavy-quark spin symmetries strongly constrain the matrix elements, leading to single form factors for $ccb\to ccc$, $bbc\to ccb$, and $bbb\to bbc$ baryon decays. We also study the effects on these systems of using a $Y$-shaped confinement potential, as suggested by lattice QCD results for the interaction between three static quarks.

Based on the effective Lagrangian approach, the $J/\psi \to p\overline{p}\varphi$ decay is studied in an isobar resonance model with the assumption that the $\varphi$-meson is produced from intermediate nucleon resonances. The contributions from the $N_{1/2^{-}}^{*}(1535)$, $N_{3/2^{+}}^{*}(1900)$, $N_{1/2^{-}}^{*}(2090)$ and $N_{1/2^{+}}^{*}(2100)$ states are considered. In terms of the coupling constants $g_{\varphi N{N}^{*}}^2$ and $g_{\psi N{N}^{*}}^2$ extracted from the reaction cross section of the ${\pi }^{-}p\to n\varphi$ process, and the partial decay widths of the $J/\psi \to p\overline{p}\eta$ and $J/\psi \to p\overline{n}{\pi }^{-}$ processes, respectively, the invariant mass spectrum and the Dalitz plot for $J/\psi \to p\overline{p}\varphi$ decay are predicted. It is shown that there are two types of results. In the type I case, a large peak structure around 2.09 GeV implies that a considerable amount of $N\varphi$ or $qqqs\overline{s}$ component may exist in the narrow-width $N_{1/2^{-}}^{*}(2090)$ state, but a tiny $qqqs\overline{s}$ component in the broad-width $N_{1/2^{+}}^{*}(2100)$ state. In the type II case, a small peak around 2.11 GeV may only indicate the existence of a certain amount of $p\varphi$ or $qqqs\overline{s}$ component in the narrow-width $N_{1/2^{+}}^{*}(2100)$ state, but no information for the broad-width $N_{1/2^{-}}^{*}(2090)$ state. Further BESIII data with high statistics would help us to distinguish the strange structures of these $N^{*}$s.

We have considered the contribution of fermionic vacuum loop in the effective potential of Polyakov loop extended quark-meson model (PQM) for the two-quark flavor case and explored the phase structure and thermodynamics of the resulting PQMVT model (Polyakov-quark-meson model with vacuum term) in detail at nonzero as well as zero chemical potential. The temperature variations of order parameters and their derivatives have been calculated and the phase diagram together with the location of critical end point (CEP) has been obtained in $\mu$, and $T$ plane in both the models PQMVT and PQM. The PQMVT model analysis has been compared with the calculations in PQM model in order to bring out the effect of fermionic vacuum term on the physical observables. The sensitivity of the phase structure and location of the CEP to the choice of Polyakov loop potential and sigma meson mass value has also been explored in the PQMVT model. We notice that the CEP which is located near the temperature axis at ($\mu =81\mathrm{MeV}$, $T=167\mathrm{MeV}$) in the PQM model gets shifted close to the chemical potential axis at (${\mu }_{\mathrm{CEP}}=294.7$, $T_{\mathrm{CEP}}=84.0\mathrm{MeV}$) in the PQMVT model calculations of the phase diagram. Since it emerges from a background of second-order transition in the chiral limit of massless quarks, the crossover occurring at $\mu =0$ in PQMVT model for the realistic case of explicitly broken chiral symmetry, has been identified as quite a soft and smooth transition. We have presented and compared the results for temperature variations of thermodynamic observables at zero and different nonzero quark chemical potentials. It is noticed that the presence of fermionic vacuum term in the effective potential leads to a smoother and slower temperature variation of thermodynamic quantities.

In this paper, we explore the possibility of spontaneous $CP$ violation in the scattering of quarks and antiquarks from QCD $Z(3)$ domain walls. The $CP$ violation here arises from the nontrivial profile of the background gauge field $(A_0)$ between different $Z(3)$ vacua. We calculate the spatial variation of $A_0$ across the Z(3) interface from the profile of the Polyakov loop $L(\overrightarrow{x})$ for the Z(3) interface and calculate the reflection of quarks and antiquarks using the Dirac equation. This spontaneous $CP$ violation has interesting consequences for the relativistic heavy-ion collision experiments, such as baryon enhancement at high $P_T$. It also acts as a source of additional $J/\psi$ suppression. We also discuss its implications for the early Universe.

In addition to three active neutrinos ${\nu }_e$, ${\nu }_{\mu }$, and ${\nu }_{\tau }$, one or more light sterile neutrinos have been conjectured to account for the LSND, MiniBooNE, and reactor antineutrino anomalies (at the sub-eV mass scale) or for warm dark matter in the Universe (at the keV mass scale). Heavy Majorana neutrinos at or above the TeV scale have also been assumed in some seesaw models. Such hypothetical particles can weakly mix with active neutrinos, and thus their existence can be detected at low energies. In the $(3+3)$ scenario with three sterile neutrinos we present a full parametrization of the $6\times 6$ flavor mixing matrix in terms of 15 rotation angles and 15 phase angles. We show that this standard parametrization allows us to clearly describe the salient features of some problems in neutrino phenomenology, such as (a) possible contributions of light sterile neutrinos to the tritium beta decay and neutrinoless double-beta decay, (b) leptonic $CP$ violation and deformed unitarity triangles of the $3\times 3$ flavor mixing matrix of three active neutrinos, (c) a reconstruction of the $6\times 6$ neutrino mass matrix in the type-(I+II) seesaw mechanism, and (d) flavored and unflavored leptogenesis scenarios in the type-I seesaw mechanism with three heavy Majorana neutrinos.

A search is performed for heavy particle pairs produced in $\sqrt{s}=7\mathrm{TeV}$ proton-proton collisions with $35{\mathrm{pb}}^{-1}$ of data collected by the CMS experiment at the LHC. The search is sensitive to squarks and gluinos of generic supersymmetry models, provided they are kinematically accessible, with minimal assumptions on properties of the lightest superpartner particle. The kinematic consistency of the selected events is tested against the hypothesis of heavy particle pair production using the dimensionless razor variable $R$, related to the missing transverse energy $E_{\mathrm{T}}^{\mathrm{miss}}$. The new physics signal is characterized by a broad peak in the distribution of $M_R$, an event-by-event indicator of the heavy particle mass scale. This new approach is complementary to $E_{\mathrm{T}}^{\mathrm{miss}}$-based searches. After background modeling based on data, and background rejection based on $R$ and $M_R$, no significant excess of events is found beyond the standard model expectations. The results are interpreted in the context of the constrained minimal supersymmetric standard model as well as two simplified supersymmetry models.

The ATLAS experiment has measured the production cross section of events with two isolated photons in the final state, in proton-proton collisions at $\sqrt{s}=7\mathrm{TeV}$. The full data set acquired in 2010 is used, corresponding to an integrated luminosity of $37{\mathrm{pb}}^{-1}$. The background, consisting of hadronic jets and isolated electrons, is estimated with fully data-driven techniques and subtracted. The differential cross sections, as functions of the di-photon mass ($m_{\gamma \gamma }$), total transverse momentum ($p_{\mathrm{T},\gamma \gamma }$), and azimuthal separation ($\Delta {\varphi }_{\gamma \gamma }$), are presented and compared to the predictions of next-to-leading-order QCD.