The 50 most-cited articles in Physics Letters B, 2018

Among Swampland conditions, the distance conjecture characterizes the geometry of scalar fields and the de Sitter conjecture constrains allowed potentials on it. We point out a connection between the distance conjecture and a refined version of the de Sitter conjecture in any parametrically controlled regime of string theory by using Bousso's covariant entropy bound. The refined version turns out to evade all counter-examples at scalar potential maxima that have been raised. We comment on the relation of our result to the Dine–Seiberg problem.

We present a new global fit of neutrino oscillation parameters within the simplest three-neutrino picture, including new data which appeared since our previous analysis [1] . In this update we include new long-baseline neutrino data involving the antineutrino channel in T2K, as well as new data in the neutrino channel, data from NO ν A, as well as new reactor data, such as the Daya Bay 1230 days electron antineutrino disappearance spectrum data and the 1500 live days prompt spectrum from RENO, as well as new Double Chooz data. We also include atmospheric neutrino data from the IceCube DeepCore and ANTARES neutrino telescopes and from Super-Kamiokande. Finally, we also update our solar oscillation analysis by including the 2055-day day/night spectrum from the fourth phase of the Super-Kamiokande experiment. With the new data we find a preference for the atmospheric angle in the upper octant for both neutrino mass orderings, with maximal mixing allowed at Δ χ 2 = 1.6 ( 3.2 ) for normal (inverted) ordering. We also obtain a strong preference for values of the CP phase δ in the range […

We study constraints imposed by two proposed string Swampland criteria on cosmology. These criteria involve an upper bound on the range traversed by scalar fields as well as a lower bound on |∇ϕV|/V when V>0. We find that inflationary models are generically in tension with these two criteria. Applying these same criteria to dark energy in the present epoch, we find that specific quintessence models can satisfy these bounds and, at the same time, satisfy current observational constraints. Assuming the two Swampland criteria are valid, we argue that the universe will undergo a phase transition within a few Hubble times. These criteria sharpen the motivation for future measurements of the tensor-to-scalar ratio r and the dark energy equation of state w, and for tests of the equivalence principle for dark matter.

Employing the modified entropy–area relation suggested by Tsallis and Cirto [1] , and the holographic hypothesis, a new holographic dark energy (HDE) model is proposed. Considering a flat Friedmann–Robertson–Walker (FRW) universe in which there is no interaction between the cosmos sectors, the cosmic implications of the proposed HDE are investigated. Interestingly enough, we find that the identification of IR-cutoff with the Hubble radius, can lead to the late time accelerated Universe even in the absence of interaction between two dark sectors of the Universe. This is in contrast to the standard HDE model with Hubble cutoff, which does not imply the accelerated expansion, unless the interaction is taken into account.

The observation of Higgs boson production in association with a top quark pair ( t t ¯ H ), based on the analysis of proton–proton collision data at a centre-of-mass energy of 13 TeV recorded with the ATLAS detector at the Large Hadron Collider, is presented. Using data corresponding to integrated luminosities of up to 79.8 fb −1 , and considering Higgs boson decays into b b ¯ , W W ⁎ , τ + τ − , γγ , and Z Z ⁎ , the observed significance is 5.8 standard deviations, compared to an expectation of 4.9 standard deviations. Combined with the t t ¯ H searches using a dataset corresponding to integrated luminosities of 4.5 fb −1 at 7 TeV and 20.3 fb −1 at 8 TeV, the observed (expected) significance is 6.3 (5.1) standard deviations. Assuming Standard Model branching fractions, the total t t ¯ H production cross section at 13 TeV is measured to be 670 ± 90 (stat.) − 100 + 110 (syst.) fb, in agreement with the Standard Model prediction.

Recently, the Rényi and Tsallis generalized entropies have extensively been used in order to study various cosmological and gravitational setups. Here, using a special type of generalized entropy, a generalization of both the Rényi and Tsallis entropy, together with holographic principle , we build a new model for holographic dark energy. Thereinafter, considering a flat FRW universe, filled by a pressureless component and the new obtained dark energy model, the evolution of cosmos has been investigated showing satisfactory results and behavior. In our model, the Hubble horizon plays the role of IR cutoff, and there is no mutual interaction between the cosmos components. Our results indicate that the generalized entropy formalism may open a new window to become more familiar with the nature of spacetime and its properties.

We show how to decoupling two spherically symmetric and static gravitational sources through the most general possible extension of the so-called Minimal Geometric Deformation-decoupling. As a test, we decouple the Einstein–Maxwell system and reproduce the Reissner–Nordstrom solution. We show the potential of this method to study i) the consequences of modified gravity on general relativity , ii) to investigate the conjectured dark matter , and iii) to study hairy black holes.

We present a three-site Pati–Salam gauge model able to explain the Standard Model flavor hierarchies while, at the same time, accommodating the recent experimental hints of lepton-flavor non-universality in B decays. The model is consistent with low- and high-energy bounds, and predicts a rich spectrum of new states at the TeV scale that could be probed in the near future by the high- p T experiments at the LHC.

A search for the decay of the Standard Model Higgs boson into a b b ¯ pair when produced in association with a W or Z boson is performed with the ATLAS detector. The data, corresponding to an integrated luminosity of 79.8 fb − 1 were collected in proton–proton collisions during Run 2 of the Large Hadron Collider at a centre-of-mass energy of 13 TeV . For a Higgs boson mass of 125 GeV , an excess of events over the expected background from other Standard Model processes is found with an observed (expected) significance of 4.9 (4.3) standard deviations. A combination with the results from other searches in Run 1 and in Run 2 for the Higgs boson in the b b ¯ decay mode is performed, which yields an observed (expected) significance of 5.4 (5.5) standard deviations, thus providing direct observation of the Higgs boson decay into b -quarks. The ratio of the measured event yield for a Higgs boson decaying into b b ¯ to the Standard Model expectation is 1.01 ± 0.12 ( stat . ) − 0.15 + 0.16 ( syst . ) . Additionally, a combination of Run 2 results searching for the Higgs boson produced in…

Bayesian neural network (BNN) approach is employed to improve the nuclear mass predictions of various models. It is found that the noise error in the likelihood function plays an important role in the predictive performance of the BNN approach. By including a distribution for the noise error, an appropriate value can be found automatically in the sampling process, which optimizes the nuclear mass predictions. Furthermore, two quantities related to nuclear pairing and shell effects are added to the input layer in addition to the proton and mass numbers. As a result, the theoretical accuracies are significantly improved not only for nuclear masses but also for single-nucleon separation energies. Due to the inclusion of the shell effect, in the unknown region, the BNN approach predicts a similar shell-correction structure to that in the known region, e.g., the predictions of underestimation of nuclear mass around the magic numbers in the relativistic mean-field model. This manifests that better predictive performance can be achieved if more physical features are included in the BNN…

Rastall gravity, originally developed in 1972, is currently undergoing a significant surge in popularity. Rastall gravity purports to be a modified theory of gravity, with a non-conserved stress–energy tensor, and an unusual non-minimal coupling between matter and geometry, the Rastall stress–energy satisfying . Unfortunately, a deeper look shows that Rastall gravity is completely equivalent to Einstein gravity — usual general relativity. The gravity sector is completely standard, based as usual on the Einstein tensor, while in the matter sector Rastall's stress–energy tensor corresponds to an artificially isolated part of the physical conserved stress–energy.

A measurement of the H → τ τ signal strength is performed using events recorded in proton–proton collisions by the CMS experiment at the LHC in 2016 at a center-of-mass energy of 13 TeV . The data set corresponds to an integrated luminosity of 35.9 fb − 1 . The H → τ τ signal is established with a significance of 4.9 standard deviations, to be compared to an expected significance of 4.7 standard deviations. The best fit of the product of the observed H → τ τ signal production cross section and branching fraction is 1.09 − 0.26 + 0.27 times the standard model expectation. The combination with the corresponding measurement performed with data collected by the CMS experiment at center-of-mass energies of 7 and 8 TeV leads to an observed significance of 5.9 standard deviations, equal to the expected significance. This is the first observation of Higgs boson decays to τ leptons by a single experiment.

We propose a novel method to compute multi-loop master integrals by constructing and numerically solving a system of ordinary differential equations, with almost trivial boundary conditions. Thus it can be systematically applied to problems with arbitrary kinematic configurations. Numerical tests show that our method can not only achieve results with high precision, but also be much faster than the only existing systematic method sector decomposition. As a by product, we find a new strategy to compute scalar one-loop integrals without reducing them to master integrals.

A new swampland criterion has recently been proposed. As a consequence, it forbids the existence of de Sitter solutions in a low energy effective theory of a quantum gravity. However, there exist classical de Sitter solutions of ten-dimensional (10d) type II supergravities, even though they are unstable. This appears at first sight in contradiction with the criterion. Beyond possible doubts on the validity of these solutions, we propose two answers to this apparent puzzle. A first possibility is that the known 10d solutions always exhibit an energy scale of order or higher than a Kaluza–Klein scale, as we argue. A corresponding 4d low energy effective theory would then differ from the usual consistent truncations, and as we explain, would not admit a de Sitter solution. This would reconcile the existence of these 10d de Sitter solutions with the 4d criterion. A second, alternative possibility is to have a refined swampland criterion, that we propose. It forbids to have both the existence and the stability of a de Sitter solution, while unstable solutions are still allowed.

DANSS is a highly segmented 1 m3 plastic scintillator detector. Its 2500 one meter long scintillator strips have a Gd-loaded reflective cover. The DANSS detector is placed under an industrial 3.1 GWth reactor of the Kalinin Nuclear Power Plant 350 km NW from Moscow. The distance to the core is varied on-line from 10.7 m to 12.7 m. The reactor building provides about 50 m water-equivalent shielding against the cosmic background. DANSS detects almost 5000 ν˜e per day at the closest position with the cosmic background less than 3%. The inverse beta decay process is used to detect ν˜e. Sterile neutrinos are searched for assuming the 4ν model (3 active and 1 sterile ν). The exclusion area in the Δm142,sin2⁡2θ14 plane is obtained using a ratio of positron energy spectra collected at different distances. Therefore results do not depend on the shape and normalization of the reactor ν˜e spectrum, as well as on the detector efficiency. Results are based on 966 thousand antineutrino events collected at three different distances from the reactor core. The excluded area covers a wide range of…

We show that polar materials are excellent targets for direct detection of sub-GeV dark matter due to the presence of gapped optical phonons as well as acoustic phonons with high sound speed. We take the example of Gallium Arsenide (GaAs), which has the properties needed for experimental realization, and where many results can be estimated analytically. We find GaAs has excellent reach to dark photon absorption , can completely cover the freeze-in benchmark for scattering via an ultralight dark photon, and is competitive with other proposals to detect sub-MeV dark matter scattering off nuclei.

Energy conditions can play an important role in defining the cosmological evolution. Specifically acceleration/deceleration of cosmic fluid, as well as the emergence of Big Rip singularities, can be related to the constraints imposed by the energy conditions. Here we discuss this issue for f(R) gravity considering also conformal transformations. Cosmological solutions and equations of state can be classified according to energy conditions. The qualitative change of some energy conditions when transformation from the Jordan frame to the Einstein frame done is also observed.

We combine new analysis of the stochastic gravitational wave background to be expected from cosmic strings with the latest pulsar timing array (PTA) limits to give an upper bound on the energy scale of the possible cosmic string network, Gμ<1.5×10−11 at the 95% confidence level. We also show bounds from LIGO and to be expected from LISA and BBO. Current estimates for the gravitational wave background from supermassive black hole binaries are at the level where a PTA detection is expected. But if PTAs do observe a background soon, it will be difficult in the short term to distinguish black holes from cosmic strings as the source, because the spectral indices from the two sources happen to be quite similar. If PTAs do not observe a background, then the limits on Gμ will improve somewhat, but a string network with Gμ substantially below 10−11 will produce gravitational waves primarily at frequencies too high for PTA observation, so significant further progress will depend on intermediate-frequency observatories such as LISA, DECIGO and BBO.

We construct a model of quark–lepton unification at the TeV scale based on an SU(4) gauge symmetry, while still having acceptable neutrino masses and enough suppression in flavor changing neutral currents. An approximate U(2) flavor symmetry is an artifact of family-dependent gauge charges leading to a natural realization of the CKM mixing matrix. The model predicts sizeable violation of PMNS unitarity as well as a gauge vector leptoquark U1μ=(3,1,2/3) which can be produced at the LHC – both effects within the reach of future measurements. In addition, recently reported experimental anomalies in semi-leptonic B-meson decays, both in charged b→cτν and neutral b→sμμ currents, can be accommodated.

The transverse momentum ( p T ) spectrum of prompt D 0 mesons and their antiparticles has been measured via the hadronic decay channels D 0 → K − π + and D ‾ 0 → K + π − in p p and PbPb collisions at a centre-of-mass energy of 5.02 TeV per nucleon pair with the CMS detector at the LHC. The measurement is performed in the D 0 meson p T range of 2–100 GeV/ c and in the rapidity range of | y | < 1 . The p p (PbPb) dataset used for this analysis corresponds to an integrated luminosity of 27.4 pb −1 (530 μb −1 ). The measured D 0 meson p T spectrum in pp collisions is well described by perturbative QCD calculations. The nuclear modification factor, comparing D 0 meson yields in PbPb and p p collisions, was extracted for both minimum-bias and the 10% most central PbPb interactions. For central events, the D 0 meson yield in the PbPb collisions is suppressed by a factor of 5–6 compared to the p p reference in the p T range of 6–10 GeV/ c . For D 0 mesons in the high- p T range of 60–100 GeV/ c , a significantly smaller suppression is observed. The results are also compared to theoretical…

It was shown by Tsallis and Cirto that thermodynamical entropy of a gravitational system such as black hole must be generalized to the non-additive entropy, which is given by Sh=γAβ, where A is the horizon area and β is the nonextensive parameter [1]. In this paper, by taking the entropy associated with the apparent horizon of the Friedmann–Robertson–Walker (FRW) Universe in the form of Tsallis entropy, and assuming the first law of thermodynamics, dE=ThdSh+WdV, holds on the apparent horizon, we are able to derive the corresponding Friedmann equations describing the dynamics of the universe with any spatial curvature. We also examine the time evolution of the total entropy and show that the generalized second law of thermodynamics is fulfilled in a region enclosed by the apparent horizon. Then, modifying the emergence proposal of gravity proposed by Padmanabhan and calculating the difference between the surface degrees of freedom and the bulk degrees of freedom in a region of space, we again arrive at the modified Friedmann equation of the FRW Universe with any spatial curvature…

Angular distributions of the decay B 0 → K ⁎ 0 μ + μ − are studied using a sample of proton–proton collisions at s = 8 TeV collected with the CMS detector at the LHC, corresponding to an integrated luminosity of 20.5 fb − 1 . An angular analysis is performed to determine the P 1 and P 5 ′ parameters, where the P 5 ′ parameter is of particular interest because of recent measurements that indicate a potential discrepancy with the standard model predictions. Based on a sample of 1397 signal events, the P 1 and P 5 ′ parameters are determined as a function of the dimuon invariant mass squared. The measurements are in agreement with predictions based on the standard model.

We have computed the contributions of the quartic Casimir invariants to the four-loop anomalous dimensions of twist-2 spin-N operators at N≤16. The results provide new information on the structure of the next-to-next-to-next-to-leading order (N3LO) splitting functions Pik(3)(x) for the evolution of parton distributions, and facilitate approximate expressions which include the quartic-Casimir contributions to the (light-like) gluon cusp anomalous dimension. These quantities turn out to be closely related, by a generalization of the lower-order ‘Casimir scaling’, to the corresponding quark results. Using these findings, we present an approximate result for the four-loop gluon cusp anomalous dimension in QCD which is sufficient for phenomenological applications.

The recently claimed anomaly in the measurement of the 21 cm hydrogen absorption signal by EDGES at z∼17, if cosmological, requires the existence of new physics. The possible attempts to resolve the anomaly rely on either (i) cooling the hydrogen gas via new dark matter-hydrogen interactions or (ii) modifying the soft photon background beyond the standard CMB one, as possibly suggested also by the ARCADE 2 excess. We argue that solutions belonging to the first class are generally in tension with cosmological dark matter probes once simple dark sector models are considered. Therefore, we propose soft photon emission by light dark matter as a natural solution to the 21 cm anomaly, studying a few realizations of this scenario. We find that the signal singles out a photophilic dark matter candidate characterised by an enhanced collective decay mechanism, such as axion mini-clusters.

It is shown that the description of a relativistic fluid at local thermodynamic equilibrium depends on the particular quantum stress-energy tensor operator chosen, e.g., the canonical or symmetrized Belinfante stress-energy tensor. We argue that the Belinfante tensor is not appropriate to describe a relativistic fluid whose macroscopic polarization relaxes slowly to thermodynamic equilibrium and that a spin tensor, like the canonical spin tensor, is required. As a consequence, the description of a polarized relativistic fluid involves an extension of relativistic hydrodynamics including a new antisymmetric rank-two tensor as a dynamical field. We show that the canonical and Belinfante tensors lead to different predictions for measurable quantities such as spectrum and polarization of particles produced in relativistic heavy-ion collisions.

The first measurements of anisotropic flow coefficients v n for mid-rapidity charged particles in Xe–Xe collisions at s NN = 5.44 TeV are presented. Comparing these measurements to those from Pb–Pb collisions at s NN = 5.02 TeV, v 2 is found to be suppressed for mid-central collisions at the same centrality, and enhanced for central collisions. The values of v 3 are generally larger in Xe–Xe than in Pb–Pb at a given centrality. These observations are consistent with expectations from hydrodynamic predictions. When both v 2 and v 3 are divided by their corresponding eccentricities for a variety of initial state models, they generally scale with transverse density when comparing Xe–Xe and Pb–Pb, with some deviations observed in central Xe–Xe and Pb–Pb collisions. These results assist in placing strong constraints on both the initial state geometry and medium response for relativistic heavy-ion collisions.

Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length of the hot and dense matter created in relativistic heavy-ion collisions and can be used to search for the QCD critical point. We report the first measurements of the moments of net-kaon multiplicity distributions in Au+Au collisions at s NN = 7.7 , 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality and energy dependence of the mean ( M ), variance ( σ 2 ), skewness ( S ), and kurtosis ( κ ) for net-kaon multiplicity distributions as well as the ratio σ 2 / M and the products Sσ and κ σ 2 are presented. Comparisons are made with Poisson and negative binomial baseline calculations as well as with UrQMD, a transport model (UrQMD) that does not include effects from the QCD critical point. Within current uncertainties, the net-kaon cumulant ratios appear to be monotonic as a function of collision energy.

Feynman integrals are easily solved if their system of differential equations is in ε -form. In this letter we show by the explicit example of the kite integral family that an ε -form can even be achieved, if the Feynman integrals do not evaluate to multiple polylogarithms. The ε -form is obtained by a (non-algebraic) change of basis for the master integrals.

Using an effective σ/f0(500) resonance, which describes the ππ→ππ and γγ→ππ scattering data, we evaluate its contribution and the ones of the other scalar mesons to the hadronic light-by-light (HLbL) scattering component of the anomalous magnetic moment aμ of the muon. We obtain the conservative range of values: ∑Saμlbl|S≃−(4.51±4.12)×10−11, which is dominated by the σ/f0(500) contribution (50%∼98%), and where the large error is due to the uncertainties on the parametrisation of the form factors. Considering our new result, we update the sum of the different theoretical contributions to aμ within the standard model, which we then compare to experiment. This comparison gives (aμexp−aμSM)=+(312.1±64.6)×10−11, where the theoretical errors from HLbL are dominated by the scalar meson contributions.

We present a microscopic model for collective effects in high multiplicity proton–proton collisions, where multiple partonic subcollisions give rise to a dense system of strings. From lattice calculations we know that QCD strings are transversely extended, and we argue that this should result in a transverse pressure and expansion, similar to the flow in a deconfined plasma. The model is implemented in the P ythia 8 Monte Carlo event generator, and we find that it can qualitatively reproduce the long range azimuthal correlations forming a near-side ridge in high multiplicity proton–proton events at LHC energies.

The concept of effective dynamics has proven successful in LQC, a loop-inspired quantization of cosmological spacetimes. We apply the same idea of its derivation in LQC to the full theory, by computing the expectation value of the scalar constraint with respect to some coherent states peaked on the phase-space variables of flat Robertson–Walker spacetime. We comment on the relation with effective LQC and find a deviation stemming from the Lorentzian part of the Hamiltonian.

Relaxing the Riemannian condition to incorporate geometric quantities such as torsion and non-metricity may allow to explore new physics associated with defects in a hypothetical space–time microstructure. Here we show that non-metricity produces observable effects in quantum fields in the form of 4-fermion contact interactions, thereby allowing us to constrain the scale of non-metricity to be greater than 1 TeV by using results on Bahbah scattering. Our analysis is carried out in the framework of a wide class of theories of gravity in the metric-affine approach. The bound obtained represents an improvement of several orders of magnitude to previous experimental constraints.

We analyze the motion of a massless and chargeless particle very near to the event horizon. It reveals that the radial motion has exponential growing nature which indicates that there is a possibility of inducing chaos in the particle motion of an integrable system when it comes under the influence of the horizon. This is being confirmed by investigating the Poincaré section of the trajectories with the introduction of a harmonic trap to confine the particle's motion. Two situations are investigated: (a) any static, spherically symmetric black hole and, (b) spacetime represents a stationary, axisymmetric black hole (e.g., Kerr metric). In both cases, the largest Lyapunov exponent has upper bound which is the surface gravity of the horizon. We find that the inclusion of rotation in the spacetime introduces more chaotic fluctuations in the system. The possible implications are finally discussed.

We show that introducing R2-term makes the Higgs-inflation and Higgs-dilaton inflation consistent models: the strong coupling energy scales in scalar, gauge and gravity sectors all are lifted up to the Planck scale.

We derive a new bound on diphoton resonances using inclusive diphoton cross section measurements at the LHC, in the so-far poorly constrained mass range between the Upsilon and the SM Higgs. This bound sets the current best limit on axion-like particles that couple to gluons and photons, for masses between 10 and 65 GeV. We also estimate indicative sensitivities of a dedicated diphoton LHC search in the same mass region, at 7, 8 and 14 TeV. As a byproduct of our analysis, we comment on the axion-like particle interpretation of the CMS excesses in low-mass dijet and diphoton searches.

It is generally believed that the quark-hadron transition at small values of baryon chemical potentials μB is a crossover but changes to a first-order phase transition with an associated critical endpoint (CEP) as μB increases. Such a μB-dependent quark-hadron transition is expected to result in a double-peak structure in the collision energy dependence of the baryon density fluctuation in heavy-ion collisions with one at lower energy due to the spinodal instability during the first-order phase transition and another at higher energy due to the critical fluctuations in the vicinity of the CEP. By analyzing the data on the p, d and 3H yields in central heavy-ion collisions within the coalescence model for light nuclei production, we find that the relative neutron density fluctuation Δρn=〈(δρn)2〉/〈ρn〉2 at kinetic freeze-out indeed displays a clear peak at sNN=8.8GeV and a possible strong re-enhancement at sNN=4.86GeV. Our findings thus provide a strong support for the existence of a first-order phase transition at large μB and its critical endpoint at a smaller μB in the temperature…

A search for the standard model (SM) Higgs boson (H) decaying to b b ‾ when produced in association with an electroweak vector boson is reported for the following processes: Z ( ν ν ) H , W ( μ ν ) H , W ( e ν ) H , Z ( μ μ ) H , and Z ( e e ) H . The search is performed in data samples corresponding to an integrated luminosity of 35.9 fb −1 at s = 13 TeV recorded by the CMS experiment at the LHC during Run 2 in 2016. An excess of events is observed in data compared to the expectation in the absence of a H → b b ‾ signal. The significance of this excess is 3.3 standard deviations, where the expectation from SM Higgs boson production is 2.8. The signal strength corresponding to this excess, relative to that of the SM Higgs boson production, is 1.2 ± 0.4 . When combined with the Run 1 measurement of the same processes, the signal significance is 3.8 standard deviations with 3.8 expected. The corresponding signal strength, relative to that of the SM Higgs boson, is 1.06 − 0.29 + 0.31 .

A search is presented for new physics in events with two low-momentum, oppositely charged leptons (electrons or muons) and missing transverse momentum in proton-proton collisions at a centre-of-mass energy of 13 TeV. The data collected using the CMS detector at the LHC correspond to an integrated luminosity of 35.9 fb − 1 . The observed event yields are consistent with the expectations from the standard model. The results are interpreted in terms of pair production of charginos and neutralinos ( χ ˜ 1 ± and χ ˜ 2 0 ) with nearly degenerate masses, as expected in natural supersymmetry models with light higgsinos, as well as in terms of the pair production of top squarks ( t ˜ ), when the lightest neutralino and the top squark have similar masses. At 95% confidence level, wino-like χ ˜ 1 ± / χ ˜ 2 0 masses are excluded up to 230 GeV for a mass difference of 20 GeV relative to the lightest neutralino. In the higgsino-like model, masses are excluded up to 168 GeV for the same mass difference. For t ˜ pair production, top squark masses up to 450 GeV are excluded for a mass difference of…

A search for the production of Higgs boson pairs in proton–proton collisions at a centre-of-mass energy of 13 TeV is presented, using a data sample corresponding to an integrated luminosity of 35.9 fb −1 collected with the CMS detector at the LHC. Events with one Higgs boson decaying into two bottom quarks and the other decaying into two τ leptons are explored to investigate both resonant and nonresonant production mechanisms. The data are found to be consistent, within uncertainties, with the standard model background predictions. For resonant production, upper limits at the 95% confidence level are set on the production cross section for Higgs boson pairs as a function of the hypothesized resonance mass and are interpreted in the context of the minimal supersymmetric standard model. For nonresonant production, upper limits on the production cross section constrain the parameter space for anomalous Higgs boson couplings. The observed (expected) upper limit at 95% confidence level corresponds to about 30 (25) times the prediction of the standard model.

The Δ-isobar degrees of freedom are included in the covariant density functional (CDF) theory to study the equation of state (EoS) and composition of dense matter in compact stars. In addition to Δ's we include the full octet of baryons, which allows us to study the interplay between the onset of delta isobars and hyperonic degrees of freedom. Using both the Hartree and Hartree–Fock approximation we find that Δ's appear already at densities slightly above the saturation density of nuclear matter for a wide range of the meson–Δ coupling constants. This delays the appearance of hyperons and significantly affects the gross properties of compact stars. Specifically, Δ's soften the EoS at low densities but stiffen it at high densities. This softening reduces the radius of a canonical 1.4M⊙ star by up to 2 km for a reasonably attractive Δ potential in matter, while the stiffening results in larger maximum masses of compact stars. We conclude that the hypernuclear CDF parametrizations that satisfy the 2M⊙ maximum mass constraint remain valid when Δ isobars are included, with the important…

By solving a simple kinetic equation, in the relaxation time approximation, and for a particular set of moments of the distribution function, we establish a set of equations which, on the one hand, capture exactly the dynamics of the kinetic equation, and, on the other hand, coincide with the hierarchy of equations of viscous hydrodynamics, to arbitrary order in the viscous corrections. This correspondence sheds light on the underlying mechanism responsible for the apparent success of hydrodynamics in regimes that are far from local equilibrium.

Transverse momentum ( p T ) spectra of charged particles at mid-pseudorapidity in Xe–Xe collisions at s NN = 5.44 TeV measured with the ALICE apparatus at the Large Hadron Collider are reported. The kinematic range 0.15 < p T < 50 GeV / c and | η | < 0.8 is covered. Results are presented in nine classes of collision centrality in the 0–80% range. For comparison, a pp reference at the collision energy of s = 5.44 TeV is obtained by interpolating between existing pp measurements at s = 5.02 and 7 TeV. The nuclear modification factors in central Xe–Xe collisions and Pb–Pb collisions at a similar center-of-mass energy of s NN = 5.02 TeV, and in addition at 2.76 TeV, at analogous ranges of charged particle multiplicity density 〈 d N ch / d η 〉 show a remarkable similarity at p T > 10 GeV / c . The centrality dependence of the ratio of the average transverse momentum 〈 p T 〉 in Xe–Xe collisions over Pb–Pb collision at s = 5.02 TeV is compared to hydrodynamical model calculations.

We explore the interplays among the formation of a halo, deformation effects, the inversion of sd states, the shell evolution, and changes of nuclear magicities in 22C by using a deformed relativistic Hartree–Bogoliubov model in continuum. It is revealed that there is an inversion between the two spherical orbitals 2s1/2 and 1d5/2 in 22C compared with the conventional single particle shell structure in stable nuclei. This inversion, together with deformation effects, results in a shrunk halo and a quenched shell gap at N=16. It is predicted that the core of 22C is oblate but the halo is prolate. Therefore several exotic nuclear phenomena, including the halo, the shape decoupling effects, the inversion of sd states, and the evolution of shell structure which results in (dis)appearance of magic numbers, coexist in one single nucleus C22.

Horizonless compact objects with light rings (or photon spheres) are becoming increasingly popular in recent years for several reasons. In this paper, we show that a horizonless object such as a wormhole of Morris–Thorne type can have two photon spheres. In particular, we show that, in addition to the one present outside a wormhole throat, the throat can itself act as an effective photon sphere. Such wormholes exhibit two sets of relativistic Einstein ring systems formed due to strong gravitational lensing. We consider a previously obtained wormhole solution as a specific example. If such type of wormhole casts a shadow at all, then the inner set of the relativistic Einstein rings will form the outer bright edge of the shadow. Such a novel lensing feature might serve as a distinguishing feature between wormholes and other celestial objects as far as gravitational lensing is concerned.

We introduce the hypothesis that diquarks and antidiquarks in tetraquarks are separated by a potential barrier. We show that this notion can answer satisfactorily long standing questions challenging the diquark–antidiquark model of exotic resonances. The tetraquark description of X and Z resonances is shown to be compatible with present limits on the non-observation of charged partners X±, of the X(3872) and the absence of a hyperfine splitting between two different neutral states. In the same picture, Zc and Zb particles are expected to form complete isospin triplets plus singlets. It is also explained why the decay rate into final states including quarkonia are suppressed with respect to those having open charm/beauty states.

In this Letter, the ALICE Collaboration presents the first measurements of the charged-particle multiplicity density, d N ch / d η , and total charged-particle multiplicity, N ch tot , in Xe–Xe collisions at a centre-of-mass energy per nucleon–nucleon pair of s NN = 5.44 TeV . The measurements are performed as a function of collision centrality over a wide pseudorapidity range of − 3.5 < η < 5 . The values of d N ch / d η at mid-rapidity and N ch tot for central collisions, normalised to the number of nucleons participating in the collision ( N part ) as a function of s NN follow the trends established in previous heavy-ion measurements. The same quantities are also found to increase as a function of N part , and up to the 5% most central collisions the trends are the same as the ones observed in Pb–Pb at a similar energy. For more central collisions, the Xe–Xe scaled multiplicities exceed those in Pb–Pb for a similar N part . The results are compared to phenomenological models and theoretical calculations based on different mechanisms for particle production in nuclear collisions.…

Motivated by the recent detection of the gravitational wave signal emitted by a binary neutron star merger, we analyse the possible impact of dark matter on such signals. We show that dark matter cores in merging neutron stars may yield an observable supplementary peak in the gravitational wave power spectral density following the merger, which could be distinguished from the features produced by the neutron components.

The mass of the Higgs boson is measured in the H → Z Z ⁎ → 4 ℓ and in the H → γ γ decay channels with 36.1 fb −1 of proton–proton collision data from the Large Hadron Collider at a centre-of-mass energy of 13 TeV recorded by the ATLAS detector in 2015 and 2016. The measured value in the H → Z Z ⁎ → 4 ℓ channel is m H Z Z ⁎ = 124.79 ± 0.37 GeV , while the measured value in the H → γ γ channel is m H γ γ = 124.93 ± 0.40 GeV . Combining these results with the ATLAS measurement based on 7 and 8 TeV proton–proton collision data yields a Higgs boson mass of m H = 124.97 ± 0.24 GeV .

In this work we present the entanglement measures of a tripartite W-State entangled system in noninertial frame through the coordinate transformation between Minkowski and Rindler. Two cases are considered, i.e., when one qubit goes in a uniform acceleration a and the others remain stationary and when two qubits undergo in a uniform acceleration and while the other is stationary. The analytical negativities for one-tangle, two-tangle and π -tangle in total are not written out explicitly except for some special cases due to complicated expressions, but we illustrate them in graphics and study their dependencies on the acceleration parameters r b and r c . We find that the negativities of the one-tangle, two-tangle and π -tangle decrease with the acceleration parameters except for the constant N A B = N B A . The negativity N C I ( A B ) and the π C I decrease faster than N A ( B C I ) and π A ( π B ) . The negativities N A C I ( N B ( A C I ) )and N B I C I decrease faster than those N A B and N A B I , respectively. It is interesting to see there exist turning points for the…

In the present paper we try to connect the Bardeen black hole with the concept of the recently proposed black hole chemistry. We study thermodynamic properties of the regular black hole with an anti-deSitter background. The negative cosmological constant Λ plays the role of the positive thermodynamic pressure of the system. After studying the thermodynamic variables, we derive the corresponding equation of state and we show that a neutral Bardeen-anti-deSitter black hole has similar phenomenology to the chemical Van der Waals fluid. This is equivalent to saying that the system exhibits criticality and a first order small/large black hole phase transition reminiscent of the liquid/gas coexistence.