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Transient Large-Scale Anisotropy in TeV Cosmic Rays due to an Interplanetary Coronal Mass Ejection
No full textInternational audienceLarge- or medium-scale cosmic ray anisotropy at TeV energies has not previously been confirmed to vary with time. Transient anisotropy changes have been observed below 150 GeV, especially near the passage of an interplanetary shock and coronal mass ejection containing a magnetic flux rope ejected by a solar storm, which can trigger a geomagnetic storm with practical consequences. In such events, cosmic rays provide remote sensing of the magnetic field properties. Here we report the observation of transient large-scale anisotropy in TeV cosmic ray ions using data from the Large High Altitude Air Shower Observatory (LHAASO). We analyze hourly skymaps of the transient cosmic ray intensity excess or deficit, the gradient of which indicates the direction and magnitude of transient large-scale anisotropy across the field of view. We observe enhanced anisotropy above typical hourly fluctuations with 5 significance during some hours of November 4, 2021, in separate data sets for four primary cosmic ray energy ranges of median energy from =0.7 to 3.1 TeV. The gradient varies with energy as , where . At a median energy 1.0 TeV, this gradient corresponds to a dipole anisotropy of at least 1%, or possibly a weaker anisotropy of higher order. This new type of observation opens the opportunity to study interplanetary magnetic structures using air shower arrays around the world, complementing existing in situ and remote measurements of plasma properties
Cygnus X-3: A variable petaelectronvolt gamma-ray source
No full textInternational audienceWe report the discovery of variable -rays up to petaelectronvolt from Cygnus X-3, an iconic X-ray binary. The -ray signal was detected with a statistical significance of approximately 10 by the Large High Altitude Air Shower Observatory (LHAASO). Its intrinsic spectral energy distribution (SED), extending from 0.06 to 3.7 PeV, shows a pronounced rise toward 1 PeV after accounting for absorption by the cosmic microwave background radiation. The detected month-scale variability,together with a 3.2 evidence for orbital modulation, suggests that the PeV -rays originate within, or in close proximity to, the binary system itself. The observed energy spectrum and temporal modulation can be naturally explained by -ray production through photomeson processes in the innermost region of the relativistic jet, where protons need to be accelerated to tens of PeV energies
Hadron Physics Opportunities at FAIR
No full textInternational audienceThis White Paper outlines a coordinated, decade-spanning programme of hadron and QCD studies anchored at the GSI/FAIR accelerator complex. Profiting from intense deuteron, proton and pion beams coupled with high-rate capable detectors and an international theory effort, the initiative addresses fundamental questions related to the strong interaction featuring confinement and dynamical mass generation. This includes our understanding of hadron-hadron interactions and the composition of hadrons through mapping the baryon and meson spectra, including exotic states, and quantifying hadron structure. This interdisciplinary research connects topics in the fields of nuclear, heavy-ion, and (nuclear) astro (particle) physics, linking, for example, terrestrial data to constraints on neutron star structure. A phased roadmap with SIS100 accelerator start-up and envisaged detector upgrades will yield precision cross sections, transition form factors, in-medium spectral functions, and validated theory inputs. Synergies with external programmes at international accelerator facilities worldwide are anticipated. The programme is expected to deliver decisive advances in our understanding of non-perturbative (strong) QCD and astrophysics, and high-rate detector and data-science technology
Stellar physics at sub-nanoradian angular resolution
No full textInternational audienceMany stars -- if they could be imaged with enough angular resolution -- would exhibit features expected from theory but not possible to extract from spectra. We may group these by increasing complexity as follows. First, smooth variations in brightness across the surface, resembling solar limb darkening but much more prominent and involving more processes in stars with fast spin or external tides. Next, there are periodic features: not only oscillations, but also convective cells and starspots, which appear to transit across a star as its spins, and exoplanets that really do transit across the star. Then, there are transients like flares. Current optical interferometers provide synthetic apertures of a few hundred metres and angular resolutions down to about nanoradian (milliarcsecond), enough to resolve some of the above features on the nearest upper main-sequence stars, giants and supergiants. Ongoing projects aims to km-scale synthetic apertures, enough to measure the radius of the nearest white dwarf. In this White Paper we briefly discuss what could be observed with synthetic apertures over km -- resolving detail on white dwarfs at the level currently possible on supergiants
Search for charged Higgs bosons decaying into top and bottom quarks in lepton+jets final states in proton-proton collisions at = 13 TeV
No full textInternational audienceA search is presented for charged Higgs bosons (H) in proton-proton (pp) collision events via the pp (b)H processes, with H decaying into top (t) and bottom (b) quarks. The search targets final states with one lepton, missing transverse momentum, and two or more b jets. The analysis is based on data collected at a center-of-mass energy of 13 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 138 fb. We search for charged Higgs bosons in the 200 GeV to 1 TeV mass range. The results are interpreted within the generalized two-Higgs-doublet model (g2HDM). This model predicts additional Yukawa couplings of the Higgs bosons to the top quark , the top and charm quark , and the top and up quark . This search focuses on the real components of and , which are probed up to values of unity. An excess is observed with respect to the standard model expectation with a local significance of 2.4 standard deviations for a signal with an H boson mass () of 600 GeV. Limits are derived on the product of the cross section (pp (b)H) and branching fraction (H tb, t b), where = e, . The values of 0.150.5 are excluded at 95% confidence level, depending on the and assumptions. The results represent the first search for charged Higgs bosons within the g2HDM framework and complement the existing results on additional neutral Higgs bosons
Standard Sirens in 2040s: Probing the Cosmic Expansion History with Gravitational Waves and Spectroscopic Galaxy Surveys
No full textInternational audienceGravitational waves (GWs) from compact binary coalescences have matured into a robust cosmological probe, providing self-calibrated luminosity distance measurements independent of any cosmic distance ladder, hence the term "standard sirens". The binary neutron star merger GW170817 delivered the first such measurement of the Hubble constant, demonstrating that GWs offer a path to precision cosmology with systematics orthogonal to standard cosmological probes. To convert GW distances into cosmological parameters, redshift information is essential. To maximize the scientific potential, the redshift must be obtained from individual galaxies, either by identifying electromagnetic counterparts of GW events (bright sirens) or by statistically associating potential hosts within the GW localization volume (dark sirens). The precision of these redshifts sets the achievable accuracy. Forecasts show that photometric uncertainties degrade cosmological constraints by up to an order of magnitude compared to spectroscopic ones. Wide-field, high-multiplex spectroscopic facilities will therefore be an essential infrastructure for GW cosmology in the 2040s
Nonlinear Relativistic Tidal Response of Neutron Stars
No full textInternational audienceWe investigate the nonlinear tidal response of relativistic neutron stars by computing the fully relativistic, static, quadratic Love numbers. Using both the worldline effective field theory for extended gravitating bodies and second-order perturbations of relativistic stellar models, we derive the nonlinear tidal deformation induced by an external gravito-electric tidal field to quadratic order. Through a suitable matching procedure, we provide for the first time the leading nonlinear tidal corrections to the conservative dynamics and gravitational-wave signal of binary systems. Quadratic Love numbers are enhanced more than the linear ones in the small-compactness limit. Because of this, despite entering the gravitational-wave phase at 8th post-Newtonian (PN) order, the leading quadratic Love number can be as important as the next-to-next-to-leading order linear tidal correction, which enters at 7th PN order, and is larger than the subleading point-particle contribution entering at 4th PN order. In particular, quadratic Love numbers can be as large as ~10% of the linear Love numbers in the late inspiral phase. Our approach provides a framework to also compute the (subleading) nonlinear effects induced by magnetic tidal fields and higher multipole moments, and sets the foundations for incorporating nonlinear tidal effects in high-precision gravitational-wave modeling
Matrix Elements and Characters of the Discrete Series ("Massive") Unitary Irreducible Representations of Sp(4,R)
No full textInternational audienceThis paper obtains the matrix elements and characters of the discrete series unitary irreducible representations (UIRs) of the Sp group. With an isomorphic relationship to the two-fold covering of SO (Sp SO), this group holds particular importance as the kinematical/relativity group within the framework of (-dimensional) anti-de Sitter spacetime
Utilizing simulated event lists in IACT gamma-ray astronomy
No full textInternational audienceWe present a new approach for calculating the IACT detector response of high-level analyses with publicly available software based on dedicated simulations of the individual observations. For each of them, a corresponding event list is exported, paralleling the event list of the actual data. The information contained in these simulated lists can be utilized flexibly, without the need for but also being able to reduce it to the standard IRF scheme. We show that standard IRFs from simulated event lists yield consistent results, illustrating the validity of the concept. To improve on the standard response generation, we then demonstrate how to calculate the final IRFs for a given analysis geometry directly from the simulated event lists. The result is a more accurate description, where the change in IRF methodology leads to considerable differences. Finally, we introduce a new method of generating background models based on simulated event lists. By properly considering observation and detector conditions, the new approach provides an accurate description of the γ-like background, exhibiting good stability and a moderate systematics level
A model-independent measurement of the CKM angle in the decays and ()
No full textInternational audienceA model-independent determination of the CKM angle is presented, using the and decays, with . This measurement is the first phase-space-binned study of these decay modes, and uses a sample of proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of fb. The phase-space bins are optimised for sensitivity to , and in each bin external inputs from the BESIII experiment are used to constrain the charm strong-phase parameters. The result of this binned analysis is , where the uncertainty includes both statistical and systematic contributions. Furthermore, when combining with existing phase-space-integrated measurements of the same decay modes, a value of is obtained, which is one of the most precise determinations of to date