We investigate the effect of axion cooling on nucleosynthesis in a massive star with $16M_{\odot }$ by a standard stellar evolution calculation. We find that axion cooling suppresses nuclear reactions in carbon, oxygen, and silicon burning phases because of the extraction of the energy. As a result, larger amounts of the already synthesized neon and magnesium remain without being consumed to produce further, heavier elements. Even in the case with axion-photon coupling constant $g_{a\gamma }={10}^{-11}{\mathrm{GeV}}^{-1}$, which is six times smaller than the current upper limit, the amount of neon and magnesium that remain just before the core-collapse supernova explosion is considerably larger than the standard value. This implies that we could give a more stringent constraint on $g_{a\gamma }$ from the nucleosynthesis of heavy elements in massive stars.

We obtain the dipolar anisotropies in the arrival directions of ultrahigh energy cosmic ray nuclei diffusing from nearby extragalactic sources. We consider mixed-composition scenarios in which different cosmic ray nuclei are accelerated up to the same maximum rigidity, so that $E<Z{E}_{\max }^p$, with $Z$ the atomic number and $E_{\max }^p$ the maximum proton energy. We adopt $E_{\max }^p\simeq 6\mathrm{EeV}$ so as to account for an increasingly heavy composition above the ankle. We obtain the anisotropies through Monte Carlo simulations that implement the cosmic ray diffusion in extragalactic turbulent fields as well as the effects of photodisintegrations and other energy losses. Dipolar anisotropies at the level of 5% to 10% at energies $\sim 10\mathrm{EeV}$ are predicted for plausible values of the source density and magnetic fields.

It is well known that the problem of the cosmological constant appears in a new light in unimodular gravity. In particular, the zero-momentum piece of the potential does not automatically produce a corresponding cosmological constant. Here we show that quantum corrections do not renormalize the classical value of this observable.

We show that emerging tension between the direct astronomical measurements at low redshifts and cosmological parameters deduced from the Planck measurements of the cosmic microwave background anisotropies can be alleviated if the dark matter consists of two fractions, the stable part being dominant with a smaller unstable fraction. The latter constitutes $\sim 10$ per cent at the recombination epoch if it has decayed by now.

Evidence for dark matter self-interactions has recently been reported based on the observation of a spatial offset between the dark matter halo and the stars in a galaxy in the cluster Abell 3827. Interpreting the offset as due to dark matter self-interactions leads to a cross section measurement of ${\sigma }_{\mathrm{DM}}/m\sim (1–1.5){\mathrm{cm}}^2{\mathrm{g}}^{-1}$, where $m$ is the mass of the dark matter particle. We use this observation to constrain singlet scalar dark matter coupled to the standard model and to two-Higgs-doublet models. We show that the most natural scenario in this class of models is very light dark matter, below about 0.1 GeV, whose relic abundance is set by freeze-in, i.e., by slow production of dark matter in the early universe via extremely tiny interactions with the Higgs boson, never reaching thermal equilibrium. We also show that the dark matter abundance can be established through the usual thermal freeze-out mechanism in the singlet scalar extension of the Yukawa-aligned two-Higgs-doublet model, but that it requires rather severe fine tuning of the singlet scalar mass.

Based on an $SU(2)\times SU(2)\times U(1)$ effective theory framework (aka $G221$ models), we investigate a leptophobic $SU(2{)}_L\times SU(2{)}_R\times U(1{)}_{B-L}$ model in which the right-handed $W^{\prime }$ boson has the mass of around 2 TeV and predominantly couples to the standard model quarks and the gauge-Higgs sector. This model could explain the resonant excesses near 2 TeV reported by the ATLAS Collaboration in the $WZ$ production decaying into hadronic final states and by the CMS Collaboration in the $Wh$ channel decaying into the $b\overline{b}\ell \nu$ and dijet final state. After imposing the constraints from the electroweak precision and current LHC data, we find that to explain the three excesses in the $WZ$, $Wh$, and dijet channels, the $SU(2{)}_R$ coupling strength $g_R$ favors the range of 0.47–0.68. In this model, given a 2 TeV $W^{\prime }$ mass, the $Z^{\prime }$ mass is predicted to favor 2–3 TeV if the doublet Higgs (LPD) is used to break the $G221$ symmetry at the TeV scale and 3–5 TeV for the triplet Higgs (LPT) scenario. Although the LPD $Z^{\prime }$ might be in tension with the current dilepton resonance searches, the heavier LPT $Z^{\prime }$ is consistent with current bounds, whose signatures can be further explored by the LHC Run 2 data.

The invisible signals of right-handed sneutrino decays originating from a $Z^{\prime }$ are analyzed at the Large Hadron Collider. The possibility of accessing these events helps disentangling the $B-L$ extension of the minimal supersymmetric standard model from more popular scenarios of supersymmetry. We assess the scope of the CERN machine in establishing the aforementioned signatures when accompanied by monojet, single-photon or $Z$-radiation probes through sophisticated signal-to-background simulations carried out in the presence of parton shower, hadronization as well as detector effects. We find substantial sensitivity to all such signals for standard luminosities at Run 2.

We study the LHC search constraints on models that extend the Standard Model with an inert, complex scalar electroweak multiplet, $\mathrm{\Sigma }$, with isospin $T=5/2$ (sextet) or $T=7/2$ (octet) and identical hypercharge to the Standard Model Higgs doublet. Imposing a global $Z_2$ symmetry under which $\mathrm{\Sigma }\to -\mathrm{\Sigma }$, the lightest member of $\mathrm{\Sigma }$ is stable, and we require that it be neutral (${\zeta }^{0,r}$) to avoid cosmological constraints from charged relics. Pair production of scalars by electroweak interactions followed by cascade decays to ${\zeta }^{0,r}$ through $W$ and $Z$ emission produces signatures similar to those of supersymmetric electroweak gauginos, and we constrain the models by recasting a collection of such searches made with data from the 8 TeV run of the LHC. We find that there is no sensitivity from these searches to the compressed spectrum regime, in which the mass splittings between the lightest and heaviest states in $\mathrm{\Sigma }$ are less than about 20 GeV. In the remaining parameter space, we find significant exclusions for $m_{{\zeta }^{0,r}}\sim 80–180\mathrm{GeV}$ in the sextet model, and $m_{{\zeta }^{0,r}}\sim 80–120\mathrm{GeV}$ in the octet model.

We present a lattice QCD calculation of the $B\to Dl\nu$ semileptonic decay form factors $f_{+}(q^2)$ and $f_0(q^2)$ for the entire physical $q^2$ range. Nonrelativistic QCD bottom quarks and highly improved staggered quark charm and light quarks are employed together with $N_f=2+1$ MILC gauge configurations. A joint fit to our lattice and BABAR experimental data allows an extraction of the Cabibbo-Kobayashi-Maskawa matrix element $|V_{cb}|$. We also determine the phenomenologically interesting ratio $R(D)=\mathcal{B}(B\to D\tau {\nu }_{\tau })/\mathcal{B}(B\to Dl{\nu }_l)$ ($l=e,\mu$). We find $|V_{cb}{|}_{\text{excl}}^{B\to D}=0.0402(17)(13)$, where the first error consists of the lattice simulation errors and the experimental statistical error and the second error is the experimental systematic error. For the branching fraction ratio we find $R(D)=0.300(8)$.

The effects of the nuclear medium on the residue, mass, and self-energy of the positive- and negative-parity $\mathrm{\Sigma }$, $\mathrm{\Lambda }$, and $\mathrm{\Xi }$ hyperons are investigated using the QCD sum-rule method. In the calculations, the general interpolating currents of hyperons with an arbitrary mixing parameter are used. We compare the results obtained in medium with those of the vacuum and calculate the shifts in the corresponding parameters. It is found that the shifts on the residues in nuclear matter are overall positive for both the positive- and negative-parity hyperons, except for the positive-parity $\mathrm{\Sigma }$ hyperon which has a negative shift. The shifts on the masses of these baryons are found to be negative. The shifts on the residues and masses of negative-parity states are large compared to those of positive-parity states. The maximum shift belongs to the residue of the negative-parity $\mathrm{\Lambda }$ hyperon. The vector self-energies gained by the positive-parity baryons are large compared to the vector self-energies of the negative-parity particles. The maximum value of the vector self-energy belongs to the positive-parity $\mathrm{\Sigma }$ hyperon. The numerical values are compared with the existing predictions in the literature.

Within the heavy-quark expansion techniques for the heavy hadron weak decays we analytically compute the coefficient of the power-suppressed dimension-five chromo-magnetic operator at next-to-leading order of QCD perturbation theory with the full dependence on the final-state quark mass. We present explicit expressions for the total width of inclusive semileptonic decays including the power-suppressed terms and for a few moments of decay differential distributions. One of the important phenomenological applications of our results is a precision analysis of the decays of bottom mesons to charmed final states and the extraction of the numerical value for the Cabibbo-Kobayashi-Maskawa matrix entry $|V_{cb}|$.

Existing data on the $e^{+}{e}^{-}\to K^{+}{K}^{-}$ cross section at the center-of-mass energy above 2.6 GeV are fitted with a sum of $\psi (3770)$ resonant and continuum contributions. Two solutions for the resonance production cross section are found with a significance of $3.2\sigma$. Data on the $e^{+}{e}^{-}\to K_S{K}_L$ cross section are used to resolve the ambiguity and to further constrain the values of the $e^{+}{e}^{-}\to \psi (3770)\to K^{+}{K}^{-}$ cross section and the interference phase. They are found to be ${\sigma }_{\psi (3770)}=0.073_{-0.044}^{+0.061}\mathrm{pb}$ and $\varphi =(309_{-35}^{+17}{)}^{°}$, respectively. The same fitting procedure for the $\psi (4160)$ resonance leads to the upper limit on the $e^{+}{e}^{-}\to \psi (4160)\to K^{+}{K}^{-}$ cross section ${\sigma }_{\psi (4160)}<0.062\mathrm{pb}$ at the 90% confidence level.

We show that the Higgs boson structure functions observable in the inclusive process $e^{-}{e}^{+}\to H+“\text{anything}”$, may reveal the presence of anomalous contributions corresponding to several types of new physics partners, Higgs boson compositeness, or invisible (dark) matter. This could be done without making a difficult or even an impossible experimental analysis of what “anything” contains. We give illustrations showing how the shapes of the various structure functions induced by such new contributions may differ from the standard predictions, thus possibly allowing their identification.

The ATLAS collaboration recently reported an excess of events in the high invariant mass tail of reconstructed diboson events. We investigate their analysis and point to possible subtleties and improvements in the jet substructure implementation and data-driven background estimates.

We compare the expected effects of so-called gravitationally enhanced depolarization of ultracold neutrons to measurements carried out in a spin-precession chamber exposed to a variety of vertical magnetic-field gradients. In particular, we have investigated the dependence upon these field gradients of spin-depolarization rates and also of shifts in the measured neutron Larmor precession frequency. We find excellent qualitative agreement, with gravitationally enhanced depolarization accounting for several previously unexplained features in the data.

We present a simultaneous measurement of the forward-backward asymmetry and the top-quark polarization in $t\overline{t}$ production in dilepton final states using $9.7{\mathrm{fb}}^{-1}$ of proton-antiproton collisions at $\sqrt{s}=1.96\mathrm{TeV}$ with the D0 detector. To reconstruct the distributions of kinematic observables we employ a matrix element technique that calculates the likelihood of the possible $t\overline{t}$ kinematic configurations. After accounting for the presence of background events and for calibration effects, we obtain a forward-backward asymmetry of $A^{t\overline{t}}=(15.0\pm 6.4(\text{stat})\pm 4.9(\text{syst}))\%$ and a top-quark polarization times spin analyzing power in the beam basis of $\kappa P=(7.2\pm 10.5(\text{stat})\pm 4.2(\text{syst}))\%$, with a correlation of $-56\%$ between the measurements. If we constrain the forward-backward asymmetry to its expected standard model value, we obtain a measurement of the top polarization of $\kappa P=(11.3\pm 9.1(\text{stat})\pm 1.9(\text{syst}))\%$. If we constrain the top polarization to its expected standard model value, we measure a forward-backward asymmetry of $A^{t\overline{t}}=(17.5\pm 5.6(\text{stat})\pm 3.1(\text{syst}))\%$. A combination with the D0 $A^{t\overline{t}}$ measurement in the $\text{lepton}+\text{jets}$ final state yields an asymmetry of $A^{t\overline{t}}=(11.8\pm 2.5(\text{stat})\pm 1.3(\text{syst}))\%$. Within their respective uncertainties, all these results are consistent with the standard model expectations.

We study relations between M-strings (one-dimensional intersections of M2-branes and M5-branes) in six dimensions and m-strings (magnetically charged monopole strings) in five dimensions. For specific configurations, we propose that the counting functions of Bogomol’nyi-Prasad-Sommerfield (BPS) bound states of M-strings capture the elliptic genus of the moduli space of m-strings. We check this proposal for the known cases, the Taub-NUT and Atiyah-Hitchin spaces, for which we find complete agreement. We further analyze the modular properties of the M-string free energies and find that they do not transform covariantly under $SL(2,\mathbb{Z})$. However, for a given number of M-strings, we show that there exists a unique combination of unrefined genus-zero free energies that transforms as a Jacobi form under a congruence subgroup of $SL(2,\mathbb{Z})$. These combinations correspond to summing over different numbers of M5-branes and make sense only if the distances between them are all equal. We explain that this is a necessary condition for the m-string moduli space to be factorizable into relative and center-of-mass parts.

We compute the radiation emitted by a particle on the innermost stable circular orbit of a rapidly spinning black hole both (a) analytically, working to leading order in the deviation from extremality and (b) numerically, with a new high-precision Teukolsky code. We find excellent agreement between the two methods. We confirm previous estimates of the overall scaling of the power radiated, but show that there are also small oscillations all the way to extremality. Furthermore, we reveal an intricate mode-by-mode structure in the flux to infinity, with only certain modes having the dominant scaling. The scaling of each mode is controlled by its conformal weight, a quantity that arises naturally in the representation theory of the enhanced near-horizon symmetry group. We find relationships to previous work on particles orbiting in precisely extreme Kerr, including detailed agreement of quantities computed here with conformal field theory (CFT) calculations performed in the context of the Kerr/CFT correspondence.

In this paper, we consider linearly charged dilatonic black holes and study their thermodynamical behavior in the context of phase transitions and thermodynamic geometry. We show that, depending on the values of the parameters, these black holes can undergo two types of phase transition. We also find that there are three critical behaviors near the critical points for these black holes: nonphysical unstable to physical stable, large to small, and small to large black-hole phase transitions. Next, we employ a thermodynamical metric to study the thermodynamical geometry of these black holes. We show that the characteristic behavior of the Ricci scalar of this metric enables one to recognize the type of phase transition and critical behavior of the black holes near phase-transition points. Finally, we will extend thermodynamical space by considering the dilaton parameter as an extensive parameter. With this consideration, we will show that the Weinhold, Ruppeiner, and Quevedo metrics provide extra divergencies that are not related to any phase-transition point, whereas our new method provides an effective mechanism to study phase transitions.