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Euclid: Constraining linearly scale-independent modifications of gravity with the spectroscopic and photometric primary probes
No full textContext. The future Euclid space satellite mission will offer an invaluable opportunity to constrain modifications to Einstein's general relativity at cosmic scales. In this paper, we focus on modified gravity models characterised, at linear scales, by a scale-independent growth of perturbations while featuring different testable types of derivative screening mechanisms at smaller non-linear scales.Aims. We considered three specific models, namely Jordan-Brans-Dicke, a scalar-tensor theory with a flat potential, the normal branch of Dvali-Gabadadze-Porrati (nDGP) gravity, a braneworld model in which our Universe is a four-dimensional brane embedded in a five-dimensional Minkowski space-time, and k-mouflage gravity, an extension of k-essence scenarios with a universal coupling of the scalar field to matter. In preparation for real data, we provide forecasts from spectroscopic and photometric primary probes by Euclid on the cosmological parameters and the additional parameters of the models, respectively, ωBD, Ωгc and ϵ2,0, which quantify the deviations from general relativity. This analysis will improve our knowledge of the cosmology of these modified gravity models.Methods. The forecast analysis employs the Fisher matrix method applied to weak lensing (WL); photometric galaxy clustering (GCph), spectroscopic galaxy clustering (GCsp) and the cross-correlation (XC) between GCph and WL. For the Euclid survey specifications, we define three scenarios that are characterised by different cuts in the maximum multipole and wave number, to assess the constraining power of non-linear scales. For each model we considered two fiducial values for the corresponding model parameter.Results. In an optimistic setting at 68.3% confidence interval, we find the following percentage relative errors with Euclid alone: for log10 ωBD, with a fiducial value of ωBD = 800, 27.1% using GCsp alone, 3.6% using GCph+WL+XC and 3.2% using GCph+WL+XC+GCsp; for log10 Ωгc, with a fiducial value of Ωгc = 0.25, we find 93.4, 20 and 15% respectively; and finally, for ϵ2,0 = −0.04, we find 3.4%, 0.15%, and 0.14%. From the relative errors for fiducial values closer to their ΛCDM limits, we find that most of the constraining power is lost. Our results highlight the importance of the constraining power from non-linear scales.Key words: cosmology: theory / large-scale structure of Universe★ This paper is published on behalf of the Euclid Consortium
Search for CP violation in the phase space of decays with the energy test
No full textA search for CP violation in and decays is reported. The search is performed using an unbinned model-independent method known as the energy test that probes local CP violation in the phase space of the decays. The data analysed correspond to an integrated luminosity of 5.4 fb collected in proton-proton collisions by the LHCb experiment at a centre-of-mass energy of = 13 TeV, amounting to approximately 950 thousand and 620 thousand signal candidates for the and modes, respectively. The method is validated using D → Kπππ and decays, where CP-violating effects are expected to be negligible, and using background-enhanced regions of the signal decays. The results are consistent with CP symmetry in both the and the decays, with p-values for the hypothesis of no CP violation of 70% and 66%, respectively.[graphic not available: see fulltext
Fraction of <math display="inline"><mrow><msub><mrow><mi>χ</mi></mrow><mrow><mi>c</mi></mrow></msub></mrow></math> Decays in Prompt <math display="inline"><mi>J</mi><mo>/</mo><mi>ψ</mi></math> Production Measured in <math display="inline"><mrow><mi>p</mi><mi>Pb</mi></mrow></math> Collisions at <math display="inline"><mrow><msqrt><mrow><msub><mrow><mi>s</mi></mrow><mrow><mi>NN</mi></mrow></msub></mrow></msqrt><mo>=</mo><mn>8.16</mn><mtext> </mtext><mtext> </mtext><mi>TeV</mi></mrow></math>
No full textThe fraction of χc1 and χc2 decays in the prompt J/ψ yield, Fχc→J/ψ=σχc→J/ψ/σJ/ψ, is measured by the LHCb detector in pPb collisions at sNN=8.16 TeV. The study covers the forward (1.5<y*<4.0) and backward (-5.0<y*<-2.5) rapidity regions, where y* is the J/ψ rapidity in the nucleon-nucleon center-of-mass system. Forward and backward rapidity samples correspond to integrated luminosities of 13.6±0.3 and 20.8±0.5 nb-1, respectively. The result is presented as a function of the J/ψ transverse momentum pT,J/ψ in the range 1<pT,J/ψ<20 GeV/c. The Fχc→J/ψ fraction at forward rapidity is compatible with the LHCb measurement performed in pp collisions at s=7 TeV, whereas the result at backward rapidity is 2.4σ larger than in the forward region for 1<pT,J/ψ<3 GeV/c. The increase of Fχc→J/ψ at low pT,J/ψ at backward rapidity is compatible with the suppression of the ψ(2S) contribution to the prompt J/ψ yield. The lack of in-medium dissociation of χc states observed in this study sets an upper limit of 180 MeV on the free energy available in these pPb collisions to dissociate or inhibit charmonium state formation
Azimuthal Angle Correlations of Muons Produced via Heavy-Flavor Decays in 5.02 TeV <math display="inline"><mrow><mi>Pb</mi><mo>+</mo><mi>Pb</mi></mrow></math> and <math display="inline"><mi>p</mi><mi>p</mi></math> Collisions with the ATLAS Detector
No full textAngular correlations between heavy quarks provide a unique probe of the quark-gluon plasma created in ultrarelativistic heavy-ion collisions. Results are presented of a measurement of the azimuthal angle correlations between muons originating from semileptonic decays of heavy quarks produced in 5.02 TeV Pb+Pb and pp collisions at the LHC. The muons are measured with transverse momenta and pseudorapidities satisfying pTμ>4 GeV and |ημ|<2.4, respectively. The distributions of azimuthal angle separation Δϕ for muon pairs having pseudorapidity separation |Δη|>0.8, are measured in different Pb+Pb centrality intervals and compared to the same distribution measured in pp collisions at the same center-of-mass energy. Results are presented separately for muon pairs with opposite-sign charges, same-sign charges, and all pairs. A clear peak is observed in all Δϕ distributions at Δϕ∼π, consistent with the parent heavy-quark pairs being produced via hard-scattering processes. The widths of that peak, characterized using Cauchy-Lorentz fits to the Δϕ distributions, are found to not vary significantly as a function of Pb+Pb collision centrality and are similar for pp and Pb+Pb collisions. This observation will provide important constraints on theoretical descriptions of heavy-quark interactions with the quark-gluon plasma
Measurement of the fraction of jet longitudinal momentum carried by <math display="inline"><msubsup><mi mathvariant="normal">Λ</mi><mi>c</mi><mo>+</mo></msubsup></math> baryons in <math display="inline"><mi>p</mi><mi>p</mi></math> collisions
No full textRecent measurements of charm-baryon production in hadronic collisions have questioned the universality of charm-quark fragmentation across different collision systems. In this work the fragmentation of charm quarks into charm baryons is probed, by presenting the first measurement of the longitudinal jet momentum fraction carried by Λc+ baryons, z∥ch, in hadronic collisions. The results are obtained in proton-proton (pp) collisions at s=13 TeV at the LHC, with Λc+ baryons and charged (track-based) jets reconstructed in the transverse momentum intervals of 3≤pTΛc+<15 GeV/c and 7≤pTjet ch<15 GeV/c, respectively. The z∥ch distribution is compared to a measurement of D0-tagged charged jets in pp collisions as well as to pythia 8 simulations. The data hints that the fragmentation of charm quarks into charm baryons is softer with respect to charm mesons, in the measured kinematic interval, as predicted by hadronization models which include color correlations beyond leading-color in the string formation
Role of chemical potential at kinetic freeze-out using Tsallis non-extensive statistics in proton-proton collisions at the Large Hadron Collider
No full textThe charged-particle transverse momentum spectra (-spectra) measured by the ALICE collaboration for pp collisions at 7 and 13 TeV have been studied using a thermodynamically consistent form of Tsallis non-extensive statistics. The Tsallis distribution function is fitted to the -spectra and the results are analyzed as a function of final state charged-particle multiplicity for various light flavor and strange particles, such as . At the LHC energies, particles and antiparticles are produced in equal numbers. However, the equality of particle and antiparticle yields at the kinetic freeze-out may imply that they have the same but opposite chemical potential which is not necessarily zero. We use an alternative procedure that makes use of parameter redundancy, by introducing a finite chemical potential at the kinetic freeze-out stage. This article emphasizes the importance of the chemical potential of the system produced in pp collisions at the LHC energies using the Tsallis distribution function which brings the system to a single freeze-out scenario
On the testability of the Károlyházy model
No full textKárolyházy's original proposal, suggesting that space-time fluctuations could be a source of decoherence in space, faced a significant challenge due to an unexpectedly high emission of radiation (13 orders of magnitude more than what was observed in the latest experiment). To address this issue, we reevaluated Károlyházy's assumption that the stochastic metric fluctuation must adhere to a wave equation. By considering more general correlation functions of space-time fluctuations, we resolve the problem and consequently revive the aforementioned proposal
Thermodynamic and configurational entropy of quantum Schwarzschild geometries
No full textWe study different entropies for coherent states representing the geometry of spherically symmetric compact systems. We show that the thermodynamic entropy reproduces the Bekenstein-Hawking result in the presence of thermal modes at the Hawking temperature if the object is a black hole and saturates the Bekenstein bound for more general compact objects. We also analyse the information entropy of the quantum coherent state without radiation and find further support against the singular Schwarzschild geometry
Astrophysical and cosmological relevance of the high-frequency features in the stochastic gravitational-wave background
No full textThe stochastic gravitational-wave background (SGWB) produced by merging neutron stars exhibits a peak in the kHz band. In this paper, we develop a theoretical framework to exploit this distinctive feature through a Markov Chain Monte Carlo analysis using a simulated dataset of SGWB measurements within this frequency range. The aim is to use the SGWB peak as an observable to constrain a set of astrophysical and cosmological parameters that accurately describe the sources of the SGWB. We examine how variations in these parameters impact the morphology of the SGWB and investigate the necessary sensitivity to effectively constrain them. Given our priors on astrophysical and cosmological parameters, and assuming a power-law integrated sensitivity curve of the order of 10-11 between 1 kHz and 5 kHz, we show that the values of the chirp mass and common envelope efficiency of the binary systems are retrieved with percent accuracy. Furthermore, the method allows for the reconstruction of the cosmological expansion history populated by these binaries, encompassing the Hubble constant, matter abundance, and the effective equation of state of dark energy
Infinite order results for charged sectors of the Standard Model
No full textWe determine anomalous dimensions of a family of fixed hypercharge operators in the Standard Model featuring the general Cabibbo-Kobayashi-Maskawa structure. The results are obtained at infinite orders in the couplings and to leading and subleading orders in the charge. The computed anomalous dimensions are shown to agree with the maximum known order in perturbation theory. We further show that the large hypercharge sector of the Standard Model is characterised by a non-Abelian vector condensation phase