TL;DR: In this article, a review of lattice results related to pion, kaon, D-meson, neutral kaon mixing, B-meon, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities is presented.
Abstract: We review lattice results related to pion, kaon, D-meson, B-meson, and nucleon physics with the aim of making them easily accessible to the nuclear and particle physics communities. More specifically, we report on the determination of the light-quark masses, the form factor $f_+(0)$ arising in the semileptonic $K \rightarrow \pi $ transition at zero momentum transfer, as well as the decay constant ratio $f_K/f_\pi $ and its consequences for the CKM matrix elements $V_{us}$ and $V_{ud}$. Furthermore, we describe the results obtained on the lattice for some of the low-energy constants of $SU(2)_L\times SU(2)_R$ and $SU(3)_L\times SU(3)_R$ Chiral Perturbation Theory. We review the determination of the $B_K$ parameter of neutral kaon mixing as well as the additional four B parameters that arise in theories of physics beyond the Standard Model. For the heavy-quark sector, we provide results for $m_c$ and $m_b$ as well as those for D- and B-meson decay constants, form factors, and mixing parameters. These are the heavy-quark quantities most relevant for the determination of CKM matrix elements and the global CKM unitarity-triangle fit. We review the status of lattice determinations of the strong coupling constant $\alpha _s$. Finally, in this review we have added a new section reviewing results for nucleon matrix elements of the axial, scalar and tensor bilinears, both isovector and flavor diagonal.
TL;DR: In this article, the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the Z -boson mass were evaluated and the five-quark hadronic contribution to was evaluated to be.
Abstract: We reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the Z -boson mass. We include newest cross-section data together with a phenomenological fit of the threshold region in the evaluation of the dispersion integrals. The precision in the individual datasets cannot be fully exploited due to discrepancies that lead to additional systematic uncertainty in particular between BABAR and KLOE data in the dominant channel. For the muon , we find for the lowest-order hadronic contribution . The full Standard Model prediction differs by from the experimental value. The five-quark hadronic contribution to is evaluated to be .
TL;DR: For the first time, predictions from pythia8 obtained with tunes based on NLO or NNLO PDFs are shown to reliably describe minimum-bias and underlying-event data with a similar level of agreement to predictions from tunes using LO PDF sets.
Abstract: New sets of CMS underlying-event parameters (“tunes”) are presented for the pythia8 event generator. These tunes use the NNPDF3.1 parton distribution functions (PDFs) at leading (LO), next-to-leading (NLO), or next-to-next-to-leading (NNLO) orders in perturbative quantum chromodynamics, and the strong coupling evolution at LO or NLO. Measurements of charged-particle multiplicity and transverse momentum densities at various hadron collision energies are fit simultaneously to determine the parameters of the tunes. Comparisons of the predictions of the new tunes are provided for observables sensitive to the event shapes at LEP, global underlying event, soft multiparton interactions, and double-parton scattering contributions. In addition, comparisons are made for observables measured in various specific processes, such as multijet, Drell–Yan, and top quark-antiquark pair production including jet substructure observables. The simulation of the underlying event provided by the new tunes is interfaced to a higher-order matrix-element calculation. For the first time, predictions from pythia8 obtained with tunes based on NLO or NNLO PDFs are shown to reliably describe minimum-bias and underlying-event data with a similar level of agreement to predictions from tunes using LO PDF sets.
TL;DR: In this article, a search for the electroweak production of charginos and sleptons decaying into final states with two electrons or muons is presented, based on 139.fb$^{-1}$ of proton-proton collisions recorded by the ATLAS detector at the Large Hadron Collider at
Abstract: A search for the electroweak production of charginos and sleptons decaying into final states with two electrons or muons is presented. The analysis is based on 139 fb$^{-1}$ of proton–proton collisions recorded by the ATLAS detector at the Large Hadron Collider at $\sqrt{s}=13$ $\text {TeV}$. Three R-parity-conserving scenarios where the lightest neutralino is the lightest supersymmetric particle are considered: the production of chargino pairs with decays via either W bosons or sleptons, and the direct production of slepton pairs. The analysis is optimised for the first of these scenarios, but the results are also interpreted in the others. No significant deviations from the Standard Model expectations are observed and limits at 95% confidence level are set on the masses of relevant supersymmetric particles in each of the scenarios. For a massless lightest neutralino, masses up to 420 $\text {Ge}\text {V}$ are excluded for the production of the lightest-chargino pairs assuming W-boson-mediated decays and up to 1 $\text {TeV}$ for slepton-mediated decays, whereas for slepton-pair production masses up to 700 $\text {Ge}\text {V}$ are excluded assuming three generations of mass-degenerate sleptons.
TL;DR: In this paper, the global status of new physics in weak effective theory at the b-quark scale, in the Standard Model effective theory above the electroweak scale, and in simplified models for new physics is analyzed.
Abstract: Following the updated measurement of the lepton flavour universality (LFU) ratio $$R_K$$ in $$B\rightarrow K\ell \ell $$ decays by LHCb, as well as a number of further measurements, e.g. $$R_{K^*}$$ by Belle and $$B_s \rightarrow \mu \mu $$ by ATLAS, we analyse the global status of new physics in $$b\rightarrow s$$ transitions in the weak effective theory at the b-quark scale, in the Standard Model effective theory above the electroweak scale, and in simplified models of new physics. We find that the data continues to strongly prefer a solution with new physics in semi-leptonic Wilson coefficients. A purely muonic contribution to the combination $$C_9 = -C_{10}$$, well suited to UV-complete interpretations, is now favoured with respect to a muonic contribution to $$C_9$$ only. An even better fit is obtained by allowing an additional LFU shift in $$C_9$$. Such a shift can be renormalization-group induced from four-fermion operators above the electroweak scale, in particular from semi-tauonic operators, able to account for the potential discrepancies in $$b \rightarrow c$$ transitions. This scenario is naturally realized in the simplified $$U_1$$ leptoquark model. We also analyse simplified models where a LFU effect in $$b\rightarrow s\ell \ell $$ is induced radiatively from four-quark operators and show that such a setup is on the brink of exclusion by LHC di-jet resonance searches.
TL;DR: In this paper, the trigger algorithms and selection were optimized to control the rates while retaining a high efficiency for physics analyses at the ATLAS experiment to cope with a fourfold increase of peak LHC luminosity from 2015 to 2018 (Run 2), and a similar increase in the number of interactions per beam-crossing to about 60.
Abstract: Electron and photon triggers covering transverse energies from 5 GeV to several TeV are essential for the ATLAS experiment to record signals for a wide variety of physics: from Standard Model processes to searches for new phenomena in both proton–proton and heavy-ion collisions. To cope with a fourfold increase of peak LHC luminosity from 2015 to 2018 (Run 2), to 2.1×1034cm-2s-1, and a similar increase in the number of interactions per beam-crossing to about 60, trigger algorithms and selections were optimised to control the rates while retaining a high efficiency for physics analyses. For proton–proton collisions, the single-electron trigger efficiency relative to a single-electron offline selection is at least 75% for an offline electron of 31 GeV, and rises to 96% at 60 GeV; the trigger efficiency of a 25 GeV leg of the primary diphoton trigger relative to a tight offline photon selection is more than 96% for an offline photon of 30 GeV. For heavy-ion collisions, the primary electron and photon trigger efficiencies relative to the corresponding standard offline selections are at least 84% and 95%, respectively, at 5 GeV above the corresponding trigger threshold.
TL;DR: In this paper, the geodesic motions in the spacetime of the spherically symmetric black hole solution were studied, and it was shown that a negative GB coupling constant is allowable, as in which case the singular behavior of the black hole can be hidden inside the event horizon.
Abstract: Recently, a novel 4D Einstein–Gauss–Bonnet gravity was formulated by Glavan and Lin (Phys Rev Lett 124(8):081301, 2020). Although whether the theory is well defined is currently debatable, the spherically symmetric black hole solution is still meaningful and worthy of study. In this paper, we study the geodesic motions in the spacetime of the spherically symmetric black hole solution. First of all, we find that a negative GB coupling constant is allowable, as in which case the singular behavior of the black hole can be hidden inside the event horizon. Then we calculate the innermost stable circular orbits for massive particles, which turn out to be monotonic decreasing functions of the GB coupling constant. Furthermore, we study the unstable photon sphere and shadow of the black hole. It is interesting to find that the proposed universal bounds on black hole size in Lu and Lyu (Phys Rev D 101(4):044059, 2020) recently can be broken when the GB coupling constant takes a negative value.
TL;DR: In this article, it was shown that the field equations of the EG theory do not admit an intrinsically four-dimensional definition, in terms of metric only, as such it does not exist in four dimensions.
Abstract: No! We show that the field equations of Einstein–Gauss–Bonnet theory defined in generic $$D>4$$ dimensions split into two parts one of which always remains higher dimensional, and hence the theory does not have a non-trivial limit to $$D=4$$. Therefore, the recently introduced four-dimensional, novel, Einstein–Gauss–Bonnet theory does not admit an intrinsically four-dimensional definition, in terms of metric only, as such it does not exist in four dimensions. The solutions (the spacetime, the metric) always remain $$D>4$$ dimensional. As there is no canonical choice of 4 spacetime dimensions out of D dimensions for generic metrics, the theory is not well defined in four dimensions.
TL;DR: FASER as mentioned in this paper is a proposed component of FASER, consisting of emulsion films interleaved with tungsten plates with a total target mass of 1.2 t.
Abstract: Neutrinos are copiously produced at particle colliders, but no collider neutrino has ever been detected. Colliders produce both neutrinos and anti-neutrinos of all flavors at very high energies, and they are therefore highly complementary to those from other sources. FASER, the Forward Search Experiment at the LHC, is ideally located to provide the first detection and study of collider neutrinos. We investigate the prospects for neutrino studies with FASER$$
u $$, a proposed component of FASER, consisting of emulsion films interleaved with tungsten plates with a total target mass of 1.2 t, to be placed on-axis at the front of FASER. We estimate the neutrino fluxes and interaction rates, describe the FASER$$
u $$ detector, and analyze the characteristics of the signals and primary backgrounds. For an integrated luminosity of $$150~\text {fb}^{-1}$$ to be collected during Run 3 of the 14 TeV LHC in 2021–23, approximately 1300 electron neutrinos, 20,000 muon neutrinos, and 20 tau neutrinos will interact in FASER$$
u $$, with mean energies of 600 GeV to 1 TeV. With such rates and energies, FASER will measure neutrino cross sections at energies where they are currently unconstrained, will bound models of forward particle production, and could open a new window on physics beyond the standard model.
TL;DR: The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and full simulation and parameterized analysis of the near detector as mentioned in this paper.
Abstract: The sensitivity of the Deep Underground Neutrino Experiment (DUNE) to neutrino oscillation is determined, based on a full simulation, reconstruction, and event selection of the far detector and a full simulation and parameterized analysis of the near detector. Detailed uncertainties due to the flux prediction, neutrino interaction model, and detector effects are included. DUNE will resolve the neutrino mass ordering to a precision of 5σ, for all δCP values, after 2 years of running with the nominal detector design and beam configuration. It has the potential to observe charge-parity violation in the neutrino sector to a precision of 3σ (5σ) after an exposure of 5 (10) years, for 50% of all δCP values. It will also make precise measurements of other parameters governing long-baseline neutrino oscillation, and after an exposure of 15 years will achieve a similar sensitivity to sin 22 θ13 to current reactor experiments.
TL;DR: In this paper, the authors investigated the shadow and photon spheres of the Gauss-Bonnet black hole with the static and infalling spherical accretions and found that the shadow is a signature of the spacetime geometry and it is hardly influenced by accretion.
Abstract: We investigate the shadows and photon spheres of the four-dimensional Gauss–Bonnet black hole with the static and infalling spherical accretions. We show that, for both cases, there always exist shadows and photon spheres. The radii of the shadows and photon spheres are independent of the profiles of accretion for a fixed Gauss–Bonnet constant, implying that the shadow is a signature of the spacetime geometry and it is hardly influenced by accretion. Because of the Doppler effect, the shadows of the infalling accretion are found to be darker than in the static case. We also investigate the effect of the Gauss–Bonnet constant on the shadow and photon spheres, and we find that the larger the Gauss–Bonnet constant is, the smaller the radii of the shadow and photon spheres will be. In particular, the observed specific intensity increases as the Gauss–Bonnet constant grows.
TL;DR: This work defines two models: an end-to-end reconstruction network which performs simultaneous particle identification and energy regression of particles when given calorimeter shower data, and a generative network which can provide reasonable modeling ofCalorimeter showers for different particle types at specified angles and energies.
Abstract: Using detailed simulations of calorimeter showers as training data, we investigate the use of deep learning algorithms for the simulation and reconstruction of single isolated particles produced in high-energy physics collisions. We train neural networks on single-particle shower data at the calorimeter-cell level, and show significant improvements for simulation and reconstruction when using these networks compared to methods which rely on currently-used state-of-the-art algorithms. We define two models: an end-to-end reconstruction network which performs simultaneous particle identification and energy regression of particles when given calorimeter shower data, and a generative network which can provide reasonable modeling of calorimeter showers for different particle types at specified angles and energies. We investigate the optimization of our models with hyperparameter scans. Furthermore, we demonstrate the applicability of the reconstruction model to shower inputs from other detector geometries, specifically ATLAS-like and CMS-like geometries. These networks can serve as fast and computationally light methods for particle shower simulation and reconstruction for current and future experiments at particle colliders.
TL;DR: In this paper, the authors reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the Z-boson mass.
Abstract: We reevaluate the hadronic vacuum polarisation contributions to the muon magnetic anomaly and to the running of the electromagnetic coupling constant at the Z-boson mass. We include newest $e^+e^- \rightarrow \mathrm{hadrons}$ cross-section data together with a phenomenological fit of the threshold region in the evaluation of the dispersion integrals. The precision in the individual datasets cannot be fully exploited due to discrepancies that lead to additional systematic uncertainty in particular between BABAR and KLOE data in the dominant $\pi ^+\pi ^-$ channel. For the muon $(g-2)/2$, we find for the lowest-order hadronic contribution $(694.0 \pm 4.0)\cdot 10^{-10}$. The full Standard Model prediction differs by $3.3\sigma $ from the experimental value. The five-quark hadronic contribution to $\alpha (m_Z^2)$ is evaluated to be $(276.0\pm 1.0)\cdot 10^{-4}$.
TL;DR: In this article, the authors used observational data from Supernovae (SNIa) Pantheon sample, as well as from direct measurements of the Hubble parameter from the cosmic chronometers (CC) sample, in order to extract constraints on the scenario of Barrow holographic dark energy.
Abstract: We use observational data from Supernovae (SNIa) Pantheon sample, as well as from direct measurements of the Hubble parameter from the cosmic chronometers (CC) sample, in order to extract constraints on the scenario of Barrow holographic dark energy. The latter is a holographic dark energy model based on the recently proposed Barrow entropy, which arises from the modification of the black-hole surface due to quantum-gravitational effects. We first consider the case where the new deformation exponent $$\Delta $$
is the sole model parameter, and we show that although the standard value $$\Delta =0$$
, which corresponds to zero deformation, lies within the $$1\sigma $$
region, a deviation is favored. In the case where we let both $$\Delta $$
and the second model parameter to be free we find that a deviation from standard holographic dark energy is preferred. Additionally, applying the Akaike, Bayesian and Deviance Information Criteria, we conclude that the one-parameter model is statistically compatible with $$\Lambda \hbox {CDM}$$
paradigm, and preferred comparing to the two-parameter one. Finally, concerning the present value of the Hubble parameter we find that it is close to the Planck value.
TL;DR: The standard model (SM) production of four top quarks in proton-proton collisions is studied by the CMS Collaboration, with limits set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models.
Abstract: The standard model (SM) production of four top quarks ($\text {t} {}{\overline{\text {t}}} \text {t} {}{\overline{\text {t}}} $) in proton–proton collisions is studied by the CMS Collaboration. The data sample, collected during the 2016–2018 data taking of the LHC, corresponds to an integrated luminosity of 137$\,\text {fb}^{-1}$ at a center-of-mass energy of 13$\,\text {TeV}$. The events are required to contain two same-sign charged leptons (electrons or muons) or at least three leptons, and jets. The observed and expected significances for the $\text {t} {}{\overline{\text {t}}} \text {t} {}{\overline{\text {t}}} $ signal are respectively 2.6 and 2.7 standard deviations, and the $\text {t} {}{\overline{\text {t}}} \text {t} {}{\overline{\text {t}}} $ cross section is measured to be $12.6^{+5.8}_{-5.2}\,\text {fb} $. The results are used to constrain the Yukawa coupling of the top quark to the Higgs boson, $y_{\text {t}}$, yielding a limit of $|y_{\text {t}}/y_{\text {t}}^{\mathrm {SM}} | < 1.7$ at $95\%$ confidence level, where $y_{\text {t}}^{\mathrm {SM}}$ is the SM value of $y_{\text {t}}$. They are also used to constrain the oblique parameter of the Higgs boson in an effective field theory framework, $\hat{H}<0.12$. Limits are set on the production of a heavy scalar or pseudoscalar boson in Type-II two-Higgs-doublet and simplified dark matter models, with exclusion limits reaching 350–470$\,\text {GeV}$ and 350–550$\,\text {GeV}$ for scalar and pseudoscalar bosons, respectively. Upper bounds are also set on couplings of the top quark to new light particles.
TL;DR: In this paper, the performance of a jet identification algorithm based on interaction networks (JEDI-net) was investigated to identify all-hadronic decays of high-momentum heavy particles produced at the LHC and distinguish them from ordinary jets originating from the hadronization of quarks and gluons.
Abstract: We investigate the performance of a jet identification algorithm based on interaction networks (JEDI-net) to identify all-hadronic decays of high-momentum heavy particles produced at the LHC and distinguish them from ordinary jets originating from the hadronization of quarks and gluons. The jet dynamics are described as a set of one-to-one interactions between the jet constituents. Based on a representation learned from these interactions, the jet is associated to one of the considered categories. Unlike other architectures, the JEDI-net models achieve their performance without special handling of the sparse input jet representation, extensive pre-processing, particle ordering, or specific assumptions regarding the underlying detector geometry. The presented models give better results with less model parameters, offering interesting prospects for LHC applications.
TL;DR: In this paper, the authors discuss the presence of ghostly instabilities for metric-affine theories constructed with higher order curvature terms and discuss different procedures to avoid the ghosts by adding additional constraints.
Abstract: We discuss the presence of ghostly instabilities for metric-affine theories constructed with higher order curvature terms We mainly focus on theories containing only the Ricci tensor and show the crucial role played by the projective symmetry The pathological modes arise from the absence of a pure kinetic term for the projective mode and the non-minimal coupling of a 2-form field contained in the connection, and which can be related to the antisymmetric part of the metric in non-symmetric gravity theories The couplings to matter are considered at length and cannot be used to render the theories stable We discuss different procedures to avoid the ghosts by adding additional constraints We finally argue how these pathologies are expected to be present in general metric-affine theories unless much care is taken in their construction
TL;DR: In this article, a relativistic anisotropic admissible compact structure is constructed by combining the class I approach with gravitational decoupling in order to generate the deformation function f(r).
Abstract: In this work we build a relativistic anisotropic admissible compact structures. To do so we combine the class I approach with gravitational decoupling in order to generate the deformation function f(r). As an example we have re-anisotropized two anisotropic matter distributions previously obtained by the class I procedure. To produce all the graphical study supporting this analysis, we have considered the data corresponding to the compact object 4U 1538-52, SMC X-1 and LMC X-4 for model 1 and Cen X-3 for model 2. In considering the last one, we have taken the constant parameter $$\alpha $$ to be $$\{-0.3;0.1;0.3\}$$. It is found that the resulting models satisfy all the general requirement in order to represent or describe realistic compact structures such as neutron or quark stars.
TL;DR: In this paper, the authors developed parameter-free predictions for the pointwise behavior of all the DF functions, including glue and sea, based on the leading-twist two-particle distribution amplitudes.
Abstract: Beginning with results for the leading-twist two-particle distribution amplitudes of $$\pi $$
- and K-mesons, each of which exhibits dilation driven by the mechanism responsible for the emergence of hadronic mass, we develop parameter-free predictions for the pointwise behaviour of all $$\pi $$
and K distribution functions (DFs), including glue and sea. The large-x behaviour of each DF meets expectations based on quantum chromodynamics; the valence-quark distributions match extractions from available data, including the pion case when threshold resummation effects are included; and at $$\zeta _5=5.2\,$$
GeV, the scale of existing measurements, the light-front momentum of these hadrons is shared as follows: $$\langle x_{\mathrm{valence}} \rangle ^\pi = 0.41(4)$$
, $$\langle x_{\mathrm{glue}} \rangle ^\pi = 0.45(2)$$
, $$\langle x_{\mathrm{sea}} \rangle ^\pi = 0.14(2)$$
; and $$\langle x_{\mathrm{valence}} \rangle ^K = 0.42(3)$$
, $$\langle x_{\mathrm{glue}} \rangle ^K = 0.44(2)$$
, $$\langle x_{\mathrm{sea}} \rangle ^K = 0.14(2)$$
. The kaon’s glue and sea distributions are similar to those in the pion, although the inclusion of mass-dependent splitting functions introduces some differences on the valence-quark domain. This study should stimulate improved analyses of existing data and motivate new experiments sensitive to all $$\pi $$
and K DFs. With little known empirically about the structure of the Standard Model’s (pseudo-) Nambu-Goldstone modes and analyses of existing, limited data being controversial, it is likely that new generation experiments at upgraded and anticipated facilities will provide the information needed to resolve the puzzles and complete the picture of these complex bound states.
TL;DR: CUPID-Mo as mentioned in this paper is a bolometric experiment to search for neutrinoless double-beta decay in half-a-year's live time, which is the state-of-the-art in the world.
Abstract: CUPID-Mo is a bolometric experiment to search for neutrinoless double-beta decay ($0
u \beta \beta $) of $^{100}\hbox {Mo}$. In this article, we detail the CUPID-Mo detector concept, assembly and installation in the Modane underground laboratory, providing results from the first datasets. The CUPID-Mo detector consists of an array of 20 $^{100}\hbox {Mo}$-enriched 0.2 kg $\hbox {Li}_2\hbox {MoO}_4$ crystals operated as scintillating bolometers at $\sim 20\hbox { mK}$. The $\hbox {Li}_2\hbox {MoO}_4$ crystals are complemented by 20 thin Ge optical bolometers to reject $\alpha $ events by the simultaneous detection of heat and scintillation light. We observe a good detector uniformity and an excellent energy resolution of 5.3 keV (6.5 keV) FWHM at 2615 keV, in calibration (physics) data. Light collection ensures the rejection of $\alpha $ particles at a level much higher than 99.9% – with equally high acceptance for $\gamma $/$\beta $ events – in the region of interest for $^{100}\hbox {Mo}0
u \beta \beta $. We present limits on the crystals’ radiopurity: $\le 3~\mu \hbox {Bq/kg}$ of $^{226}\hbox {Ra}$ and $\le 2~\mu \hbox {Bq/kg}$ of $^{232}\hbox {Th}$. We discuss the science reach of CUPID-Mo, which can set the most stringent half-life limit on the $^{100}\hbox {Mo}0
u \beta \beta $ decay in half-a-year’s livetime. The achieved results show that CUPID-Mo is a successful demonstrator of the technology developed by the LUMINEU project and subsequently selected for the CUPID experiment, a proposed follow-up of CUORE, the currently running first tonne-scale bolometric $0
u \beta \beta $ experiment.
TL;DR: In this paper, the greybody factor and the power spectra of the Hawking radiation of the massless scalar are studied numerically for the full range of various parameters, including the GB coupling constant, the cosmological constant, and the coupling constant related to the scalar filed.
Abstract: A novel 4D Einstein–Gauss–Bonnet gravity was recently formulated by Glavan and Lin [Phys. Rev. Lett. 124, 081301 (2020)]. Although this theory may run into trouble at the level of action or equations of motion, the spherically symmetric black hole solution, which can be successfully reproduced in those consistent theories of 4D EGB gravity, is still meaningful and worthy of study. In this paper, we investigate Hawking radiation in the spacetime containing such a de Sitter black hole. Both the greybody factor and the power spectra of the Hawking radiation of the massless scalar are studied numerically for the full range of various parameters, including the GB coupling constant $$\alpha $$
, the cosmological constant $$\Lambda $$
and the coupling constant related to the scalar filed $$\xi $$
. In particular, we find a negative $$\alpha $$
leads to a larger greybody factor than that of a $$\alpha \ge 0$$
. While, for the power spectra of the Hawking radiation the situation is quite the opposite. The reason is that the temperature of the black hole would be very high when $$\alpha <0$$
. Actually, we observe that the temperature would be arbitrarily high when $$\alpha $$
approaches to the lower bound.
TL;DR: In this paper, anisotropic spherically symmetric star under the background of f(R, T) gravity using the metric potentials of Tolman-Kuchowicz type (Tolman in Phys Rev 55:364, 1939; Kuchowicz in Acta Phys Pol 33:541, 1968) was studied.
Abstract: In the current article, we study anisotropic spherically symmetric strange star under the background of f(R, T) gravity using the metric potentials of Tolman–Kuchowicz type (Tolman in Phys Rev 55:364, 1939; Kuchowicz in Acta Phys Pol 33:541, 1968) as $$\lambda (r)=\ln (1+ar^2+br^4)$$ and $$
u (r)=Br^2+2\ln C$$ which are free from singularity, satisfy stability criteria and also well-behaved. We calculate the value of constants a, b, B and C using matching conditions and the observed values of the masses and radii of known samples. To describe the strange quark matter (SQM) distribution, here we have used the phenomenological MIT bag model equation of state (EOS) where the density profile ($$\rho $$) is related to the radial pressure ($$p_r$$) as $$p_r(r)=\frac{1}{3}(\rho -4B_g)$$. Here quark pressure is responsible for generation of bag constant $$B_g$$. Motivation behind this study lies in finding out a non-singular physically acceptable solution having various properties of strange stars. The model shows consistency with various energy conditions, TOV equation, Herrera’s cracking condition and also with Harrison–Zel$$'$$dovich–Novikov’s static stability criteria. Numerical values of EOS parameter and the adiabatic index also enhance the acceptability of our model.
TL;DR: In this paper, the authors studied the GW spectrum in strongly supercooled cosmological phase transitions, taking particular care of models featuring a complex scalar field with a U(1) symmetric potential.
Abstract: We study gravitational wave (GW) production in strongly supercooled cosmological phase transitions, taking particular care of models featuring a complex scalar field with a U(1) symmetric potential. We perform lattice simulations of two-bubble collisions to properly model the scalar field gradients, and compute the GW spectrum sourced by them using the thin-wall approximation in many-bubble simulations. We find that in the U(1) symmetric case the low-frequency spectrum is $$\propto \omega $$
whereas for a real scalar field it is $$\propto \omega ^3$$
. In both cases the spectrum decays as $$\omega ^{-2}$$
at high frequencies.
TL;DR: In this article, the authors measured the strangeness content of hadrons at mid-rapidity at the LHC using the ALICE detector at 7 TeV and found that strangeness production depends only on the charged particle multiplicity.
Abstract: The production rates and the transverse momentum distribution of strange hadrons at mid-rapidity ($\left| y\right| < 0.5$) are measured in proton-proton collisions at $\sqrt{s}$ = 13 TeV as a function of the charged particle multiplicity, using the ALICE detector at the LHC. The production rates of $\mathrm{K}^{0}_{S}$, $\Lambda $, $\Xi $, and $\Omega $ increase with the multiplicity faster than what is reported for inclusive charged particles. The increase is found to be more pronounced for hadrons with a larger strangeness content. Possible auto-correlations between the charged particles and the strange hadrons are evaluated by measuring the event-activity with charged particle multiplicity estimators covering different pseudorapidity regions. When comparing to lower energy results, the yields of strange hadrons are found to depend only on the mid-rapidity charged particle multiplicity. Several features of the data are reproduced qualitatively by general purpose QCD Monte Carlo models that take into account the effect of densely-packed QCD strings in high multiplicity collisions. However, none of the tested models reproduce the data quantitatively. This work corroborates and extends the ALICE findings on strangeness production in proton-proton collisions at 7 TeV.
TL;DR: In this paper, the physics case and ancillary studies for the proposed CODEX-b long-lived particle (LLP) detector, as well as for a smaller proof-of-concept demonstrator detector, CODEx-β, to be operated during Run-3 of the LHC are presented.
Abstract: This document presents the physics case and ancillary studies for the proposed CODEX-b long-lived particle (LLP) detector, as well as for a smaller proof-of-concept demonstrator detector, CODEX-β, to be operated during Run 3 of the LHC. Our development of the CODEX-b physics case synthesizes ‘top-down’ and ‘bottom-up’ theoretical approaches, providing a detailed survey of both minimal and complete models featuring LLPs. Several of these models have not been studied previously, and for some others we amend studies from previous literature: In particular, for gluon and fermion-coupled axion-like particles. We moreover present updated simulations of expected backgrounds in CODEX-b’s actively shielded environment, including the effects of shielding propagation uncertainties, high-energy tails and variation in the shielding design. Initial results are also included from a background measurement and calibration campaign. A design overview is presented for the CODEX-β demonstrator detector, which will enable background calibration and detector design studies. Finally, we lay out brief studies of various design drivers of the CODEX-b experiment and potential extensions of the baseline design, including the physics case for a calorimeter element, precision timing, event tagging within LHCb, and precision low-momentum tracking.
TL;DR: In this paper, the relation between the black hole shadow and the thermodynamics of the black holes has been investigated and it was shown that the phase structure can be reflected by the shadow radius for the spherically symmetric black hole.
Abstract: The relation between the black hole shadow and the black hole thermodynamics is investigated. We find that the phase structure can be reflected by the shadow radius for the spherically symmetric black hole. We also find that the shadow size gives correct information but the distortion of the shadow gives wrong information of the phase structure for the axially symmetric black hole.
TL;DR: In this article, a triple-differential measurement is performed as a function of the invariant mass and rapidity of the top quark system and the multiplicity of additional jets at particle level.
Abstract: Normalised multi-differential cross sections for top quark pair ($$\hbox {t}{\bar{\hbox {t}}}$$) production are measured in proton-proton collisions at a centre-of-mass energy of 13$$\,{\text {TeV}}$$ using events containing two oppositely charged leptons. The analysed data were recorded with the CMS detector in 2016 and correspond to an integrated luminosity of $$35.9{\,{\text {fb}}^{-1}} $$. The double-differential $$\hbox {t}{\bar{\hbox {t}}}$$ cross section is measured as a function of the kinematic properties of the top quark and of the $$\hbox {t}{\bar{\hbox {t}}}$$ system at parton level in the full phase space. A triple-differential measurement is performed as a function of the invariant mass and rapidity of the $$\hbox {t}{\bar{\hbox {t}}}$$ system and the multiplicity of additional jets at particle level. The data are compared to predictions of Monte Carlo event generators that complement next-to-leading-order (NLO) quantum chromodynamics (QCD) calculations with parton showers. Together with a fixed-order NLO QCD calculation, the triple-differential measurement is used to extract values of the strong coupling strength $$\alpha _{S}$$ and the top quark pole mass ($$m_{{\text {t}}}^{{\text {pole}}}$$) using several sets of parton distribution functions (PDFs). The measurement of $$m_{{\text {t}}}^{{\text {pole}}}$$ exploits the sensitivity of the $$\hbox {t}{\bar{\hbox {t}}}$$ invariant mass distribution to $$m_{{\text {t}}}^{{\text {pole}}}$$ near the production threshold. Furthermore, a simultaneous fit of the PDFs, $$\alpha _{S}$$, and $$m_{{\text {t}}}^{{\text {pole}}}$$ is performed at NLO, demonstrating that the new data have significant impact on the gluon PDF, and at the same time allow an accurate determination of $$\alpha _{S}$$ and $$m_{{\text {t}}}^{{\text {pole}}}$$. The values $$\alpha _{S}(m_{{\text {Z}}}) = 0.1135{}^{+0.0021}_{-0.0017}$$ and $$m_{{\text {t}}}^{{\text {pole}}} = 170.5 \pm 0.8 \,{\text {GeV}} $$ are extracted, which account for experimental and theoretical uncertainties, the latter being estimated from NLO scale variations. Possible effects from Coulomb and soft-gluon resummation near the $$\hbox {t}{\bar{\hbox {t}}}$$ production threshold are neglected in these parameter extractions. A rough estimate of these effects indicates an expected correction of $$m_{{\text {t}}}^{{\text {pole}}}$$ of the order of $$+1 \,{\text {GeV}} $$, which can be regarded as additional theoretical uncertainty in the current $$m_{{\text {t}}}^{{\text {pole}}}$$ extraction.
TL;DR: In this article, the authors derived the gravitational waves for f(T, B) gravity which is an extension of teleparallel gravity and demonstrate that it is equivalent to f(R) gravity by linearizing the field equations in the weak field limit approximation.
Abstract: We derive the gravitational waves for $$f\left( T, B\right) $$ gravity which is an extension of teleparallel gravity and demonstrate that it is equivalent to f(R) gravity by linearized the field equations in the weak field limit approximation. f(T, B) gravity shows three polarizations: the two standard of general relativity, plus and cross, which are purely transverse with two-helicity, massless tensor polarization modes, and an additional massive scalar mode with zero-helicity. The last one is a mix of longitudinal and transverse breathing scalar polarization modes. The boundary term B excites the extra scalar polarization and the mass of scalar field breaks the symmetry of the TT gauge by adding a new degree of freedom, namely a single mixed scalar polarization.
TL;DR: The results of a search for electroweakino pair production were given in this paper, in which the chargino ((chi) over tilde (+/-)(1)) decays into a W boson and the...
Abstract: The results of a search for electroweakino pair production pp -> (chi) over tilde (+/-)(1) (chi) over tilde (0)(2) in which the chargino ((chi) over tilde (+/-)(1)) decays into a W boson and the ...
TL;DR: In this article, the full-heavy tetraquarks were systematically investigated within the chiral quark model and the quark delocalization color screening model, and the results are qualitative consistent in two quark models.
Abstract: The full-heavy tetraquarks $$bb{\bar{b}}{\bar{b}}$$
and $$cc{\bar{c}}{\bar{c}}$$
are systematically investigated within the chiral quark model and the quark delocalization color screening model. Two structures, meson–meson and diquark–antidiquark, are considered. For the full-beauty $$bb{\bar{b}}{\bar{b}}$$
systems, there is no any bound state or resonance state in two structures in the chiral quark model, while the wide resonances with masses around $$19.1-19.4$$
GeV and the quantum numbers $$J^{P}=0^{+}$$
, $$1^{+}$$
, and $$2^{+}$$
are possible in the quark delocalization color screening model. For the full-charm $$cc{\bar{c}}{\bar{c}}$$
systems, the results are qualitative consistent in two quark models. No bound state can be found in the meson–meson configuration, while in the diquark–antidiquark configuration there may exist the resonance states, with masses range between 6.2 to 7.4 GeV, and the quantum numbers $$J^{P}=0^{+}$$
, $$1^{+}$$
, and $$2^{+}$$
. And the separation between the diquark and the antidiquark indicates that these states may be the compact resonance states. The reported state X(6900) is possible to be explained as a compact resonance state with $$IJ^{P}=00^{+}$$
in present calculation. All these full-charm resonance states are worth searching in the experiments further.