Mon·Apr 4, 2022Monday·April 4, 2022

1. 01*

   Self-interacting dark baryons

   James M. Cline🇨🇦 · Cédrick Perron🇨🇦

   Using results from lattice QCD, it is possible to quantitatively design models of dark baryons leading to velocity-dependent self-interaction cross sections that match the values needed for solving small-scale structure problems of standard cold dark matter. However it is not obvious that the main dark matter component in such models will be nucleons rather than large nuclei, or dark pions or atoms, whose scattering properties would be different. We first identify the parameters of a dark SU(3) sector analogous to QCD -- the confinement scale $\Lambda$ and pion mass $m_{\pi }$ -- needed to reproduce desired self-interaction cross sections. Then we show that these values can generically be compatible with the absence of a sufficiently stable deuteron bound state, and hence leading to no heavier nuclei, thus establishing the consistency of the scenario for self-interacting dark nucleons. The range of dark photon masses needed to avoid dominant pion or atomic dark matter is determined, as well as allowed values for the kinetic mixing parameter. The dark proton might be detected directly in future searches, by dark photon exchange.

   hep-phastro-ph.COPRD(2022)·11 citations
2. 02*

   Thermodynamic approach to proton number fluctuations in baryon-rich heavy-ion matter created at moderate collision energies

   Volodymyr Vovchenko🇺🇸 · Volker Koch🇺🇸

   We develop a framework to relate proton number cumulants measured in heavy-ion collisions within a momentum space acceptance to the susceptibilities of baryon number, assuming that particles are emitted from a fireball with uniform distribution of temperature and baryochemical potential, superimposed on a hydrodynamic flow velocity profile. The rapidity acceptance dependence of proton cumulants measured by the HADES Collaboration in $\sqrt{s_{\mathrm{NN}}}=2.4$ GeV Au-Au appears to be consistent with thermal emission of nucleons from a grand-canonical heat bath, with the extracted baryon number susceptibilities exhibiting an hierarchy ${\chi }_4^B\gg -{\chi }_3^B\gg {\chi }_2^B\gg {\chi }_1^B$. Naively, this could indicate large non-Gaussian fluctuations that might point to the presence of the QCD critical point close to the chemical freeze-out at $T\sim 70$ MeV and ${\mu }_B\sim 850-900$ MeV. However, the description of the experimental data at large rapidity acceptances becomes challenging once the effect of exact baryon number conservation is incorporated, suggesting that more theoretical and experimental studies are needed to reach a firm conclusion.

   hep-phnucl-exnucl-thPLB(2022)·10 citations
3. 03*

   The mass-degenerate SM-like Higgs and anomaly of $(g-2{)}_{\mu }$ in $\mu$-term extended NMSSM

   Liangliang Shang🇨🇳 · XiaoFeng Zhang🇨🇳 · Zhaoxia Heng🇨🇳

   We chose the $\mu$-term extended next-to-minimal supersymmetric standard model ($\mu$NMSSM) for this work, and the phenomenological research is based on the assumption of double Higgs resonance state as the Standard Model (SM)-like Higgs considering the recent $(g-2{)}_{\mu }$ result. The study also take into account a variety of experimental results, including direct detection of dark matter (DM) and searching results for sparticles at the Large Hadron Collider (LHC). We study the characteristic of DM confronted with limitations of direct detection experiments. Following that, we concentrate on the properties of the mass-degenerate SM-like Higgs bosons and explaining the anomaly of $(g-2{)}_{\mu }$. We conclude that the anomaly of $(g-2{)}_{\mu }$ can be explained in the scenario with two mass-degenerate SM-like Higgs, and there are samples that meet all current constraints and outperform SM in fitting Higgs data.

   hep-phhep-thJHEP(2022)·3 citations
4. 04*

   On the kinematic constraint in BFKL near threshold region

   Hao-yu Liu🇨🇳 · Xiao-hui Liu🇨🇳 · Yu Shi🇨🇳 · Du-xin Zheng🇨🇳 · Jian Zhou🇨🇳

   We introduce a modified Balitskii-Fadin-Kuraev-Lipatov (BFKL) equation with the rapidity veto that originates from external kinematic constraint. Though it is a formally sub-leading power contribution, such kinematic effect becomes very important especially in the threshold region, where there is no sufficient phase space for the small $x$ evolution to be fully developed. We also investigate the phenomenological consequences of the kinematic constraint BFKL equation in the forward particle production processes in pp and eA collisions. It is shown that particle yield at large transverse momentum is significantly suppressed in the threshold region.

   hep-phPRD(2022)·7 citations
5. 05*

   Net-proton number cumulant ratios as function of beam energy from an expanding nonequilibrium chiral fluid

   Christoph Herold🇹🇭 · Ayut Limphirat🇹🇭 · Poramin Saikham🇹🇭 · Marlene Nahrgang🇫🇷 · Tom Reichert🇩🇪 · Marcus Bleicher🇩🇪

   The beam energy scan program at RHIC provides data on net-proton number fluctuations with the goal to detect the QCD critical end point and first-order phase transition. Interpreting these experimental signals requires a vital understanding of the interplay of critical phenomena and the nonequilibrium dynamics of the rapidly expanding fireball. We study these aspects with a fluid dynamic expansion coupled to the explicit propagation of the chiral order parameter sigma via a Langevin equation. Assuming a sigma-proton coupling through an effective proton mass, we relate cumulants of the order parameter and the net-proton number at freeze-out and obtain observable cumulant ratios as a function of beam energy. We emphasize the role of the nonequilibrium first-order phase transition where a mixed phase with gradual freeze-out can significantly alter the cumulants. We find that the presence of a critical end point is clearly visible in the cumulant ratios for a relatively wide range of center-of-mass energies.

   hep-phnucl-thPRC(2022)·3 citations
6. 06*

   Low-lying doubly heavy baryons: Regge relation and mass scaling

   YongXin Song🇨🇳 · Duojie Jia🇨🇳 · WenXuan Zhang🇨🇳 · Atsushi Hosaka🇯🇵

   In framework of heavy-diquark$-$light-quark endowed with heavy-pair binding, we explore excited baryons $Q{Q}^{\prime }q$ containing two heavy quarks ($Q{Q}^{\prime }=cc,bb,bc$) by combining the method of Regge trajectory with the perturbative correction due to the heavy-pair interaction in baryons. Two Regge relations, one linear and the other nonlinear, are constructed semi-classically in the QCD string picture, and a mass scaling relation based on the heavy diquark-heavy antiquark symmetry are employed between the doubly heavy baryons and heavy mesons. We employ the ground-state mass estimates compatible with the observed doubly charmed baryon ${\Xi }_{cc}$ and spectra of the heavy quarkonia to determine the trajectory parameters and the binding energies of the heavy pair, and thereby compute the low-lying masses of the excited baryons ${\Xi }_{Q{Q}^{\prime }}$ and ${\Omega }_{Q{Q}^{\prime }}$ up to 2S and 1P excitations of the light quark and heavy diquark. The level spacings of heavy diquark excitations are found to be smaller generally than that of the light-quark excitations, in according with the nature of adiabatic expansion between the heavy and light-quark dynamics.

   hep-phEPJC(2023)·190 citations
7. 07*

   Three-pion scattering in Chiral Perturbation Theory

   Tomáš Husek (Lund U.)🇸🇪

   We present the results on the relativistic six-pion scattering amplitude at low energy, calculated at $\mathcal{O}(p^4)$ within the framework of the massive $\text{O}(N)$ nonlinear sigma model extended to the next-to-leading order in the chiral counting. For $N=3$, this approach corresponds to the two(-quark)-flavor Chiral Perturbation Theory. We also present the expressions for the pion mass, pion decay constant and the four-pion amplitude in the case of $N$ (meson) flavors at $\mathcal{O}(p^4)$.

   hep-phPoS(2024)·0 citations
8. 08*

   Many-quark interactions: Large-$N$ scaling and contribution to baryon masses

   F. Buisseret🇧🇪 · C. Semay🇧🇪 · C.T. Willemyns🇧🇪

   Starting from an effective Hamiltonian modelling a baryon made of $N$ identical quarks in the large-$N$ approach of QCD, we obtain analytical formulas allowing to estimate the contributions of multiquark interactions to the baryon mass. The cases of vanishing (mass spectrum) and non-vanishing (baryon melting) temperatures are treated.

   hep-phUniverse(2022)·5 citations
9. 09*

   Phenomenology of diphoton photoproduction at next-to-leading order

   Oskar Grocholski🇵🇱 · Bernard Pire🇫🇷 · Paweł Sznajder🇵🇱 · Lech Szymanowski🇵🇱 · Jakub Wagner🇵🇱

   We develop the analysis of diphoton exclusive photoproduction in the kinematics where a collinear QCD factorization framework applies, namely nearly forward large invariant mass diphoton production. We work at the leading twist level and at the next-to-leading order (NLO) in the strong coupling constant ${\alpha }_S$. We compare our predictions for cross-sections with Born order calculations for the experimental conditions accessible to JLab experiments and show the interesting sensitivity of our results to various models of generalized parton distributions (GPDs). The NLO corrections are rather large and negative but do not prevent the studied reaction from being a promising tool for the extraction of C-dd GPDs, which do not contribute to either spacelike or timelike deeply virtual Compton scattering amplitudes.

   hep-phPRD(2022)·50 citations
10. 10*

    Light-cone Sum Rule Analysis of Semileptonic Decays ${\Lambda }_b^0\to {\Lambda }_c^{+}{\ell }^{-}{\overline{\nu }}_{\ell }$

    Hui-Hui Duan🇨🇳 · Yong-Lu Liu🇨🇳 · Ming-Qiu Huang🇨🇳

    In this work, we analyze the semileptonic decay processes of ${\Lambda }_b\to {\Lambda }_c$ in the light-cone sum rule approach. In order to calculate the form factors of the ${\Lambda }_b$ baryon transition matrix element, we use the light-cone distribution amplitudes of ${\Lambda }_b$ obtained from the QCD sum rule in the heavy quark effective field theory framework. With the calculation of the six form factors of the ${\Lambda }_b\to {\Lambda }_c$ transition matrix element, the differential decay widths of ${\Lambda }_b^0\to {\Lambda }_c^{+}{\ell }^{-}{\overline{\nu }}_{\ell }(\ell =e,\mu ,\tau )$ and their absolute branching fractions are obtained. Additionally, the ratio of $R({\Lambda }_c^{+})\equiv \mathcal{B}r({\Lambda }_b^0\to {\Lambda }_c^{+}{\tau }^{-}{\overline{\nu }}_{\tau })/\mathcal{B}r({\Lambda }_b^0\to {\Lambda }_c^{+}{\mu }^{-}{\overline{\nu }}_{\mu })$ is also obtained in this work. Our results are in accord with the newest experimental result and other theoretical calculations and predictions.

    hep-phhep-exEPJC(2022)·20 citations
11. 11*

    Highly Radiating Charged Particles in a Strong Electromagnetic Field

    P. V. Sasorov🇨🇿 · M. Jirka🇨🇿 · S. V. Bulanov🇨🇿

    We consider highly radiating ultra-relativistic electrons in a strong external electromagnetic field. High intensity radiative losses and consequent $e^{+}{e}^{-}$-pair production, appearing in the frame of quantum electrodynamics, determine indirectly mass operator of electrons in the strong field. We calculate a leading term of the mass operator at asymptotically high energies of electrons in a strong constant field. We do not use any perturbation theory based on a low ratio of this mass operator to the electron mass $m_e$, but only the original small parameter of quantum electrodynamics, the fine structure constant, $\alpha$. The analogous %but less nontrivial result is obtained for the polarization operator for photon propagator. These results resolve at least partially a very long-lasted controversy originating from traditional and straightforward application of perturbative approaches for description of highly radiating ultra-relativistic charged particles in a very strong electromagnetic fields.

    hep-phphysics.plasm-ph1 citation
12. 12*

    Complementarity of experimental and lattice QCD data on pion parton distributions

    P. C. Barry🇺🇸 · C. Egerer🇺🇸 · J. Karpie🇺🇸 · W. Melnitchouk🇺🇸 · C. Monahan🇺🇸 · K. Orginos🇺🇸 · Jian-Wei Qiu🇺🇸 · D. Richards🇺🇸 · N. Sato🇺🇸 · R. S. Sufian🇺🇸 · S. Zafeiropoulos🇫🇷

    We extract pion parton distribution functions (PDFs) in a Monte Carlo global QCD analysis of experimental data together with reduced Ioffe time pseudo-distributions and matrix elements of current-current correlators generated from lattice QCD. By including both experimental and lattice QCD data, our analysis rigorously quantifies both the uncertainties of the pion PDFs and systematic effects intrinsic to the lattice QCD observables. The reduced Ioffe time pseudo-distributions significantly decrease the uncertainties on the PDFs, while the current-current correlators are limited by the systematic effects associated with the lattice. Consistent with recent phenomenological determinations, the behavior of the valence quark distribution of the pion at large momentum fraction is found to be $\sim (1-x{)}^{{\beta }_{\mathrm{eff}}}$ with ${\beta }_{\mathrm{eff}}\approx 1.0-1.2$.

    hep-phhep-exhep-latnucl-thPRD(2022)·48 citations
13. 13*

    Reach and complementarity of $\mu \to e$ searches

    Sacha Davidson🇫🇷 · Bertrand Echenard🇺🇸

    In Effective Field Theory, we describe $\mu \leftrightarrow e$ flavour changing transitions using an operator basis motivated by experimental observables. In a six-dimensional subspace probed by $\mu \to e\gamma$, $\mu \to 3e$ and $\mu \to e$ conversion on nuclei, we derive constraints on the New Physics scale from past and future experiments, illustrating the complementarity of the processes in an intuitive way. We also recall that a precise determination of the scalar quark currents in the nucleon will be required to distinguish scalar $\mu \to e$ interactions on u-quarks from those on d-quarks.

    hep-phEPJC(2022)·38 citations
14. 14*

    Searching for QGP droplets with high-$p_T$ hadrons and heavy flavor

    Weiyao Ke🇺🇸 · Ivan Vitev🇺🇸

    The search for the smallest quark-gluon plasma (QGP) droplets in nature has motivated recent small collisions system programs at RHIC and LHC. Unambiguous identification of jet quenching due to final-state interactions is key to confirming QGP formation in these reactions. We compute the nuclear modification factors $R_{AA}$ and $R_{p(d)A}$ of charged hadrons and heavy flavor mesons in large (Au-Au, Xe-Xe, Pb-Pb) and small ($d$-Au, $p$-Pb, O-O) colliding systems, respectively. Our results include the Cronin effect and initial-state parton energy loss in cold nuclear matter. In the final state, hard partons undergo collisional energy loss and branching that was recently derived using Soft-Collinear-Effective-Theory with Glauber Gluon (SCET${}_{\mathrm{G}}$). In large colliding systems, medium-modified QCD evolution of the fragmentation functions dominates the nuclear correction. As the system size decreases, we find that cold nuclear matter effects, collisional energy loss, and QGP-induced radiations can become equally important. A systematic scan over the medium size and mass/flavor dependence of $R_{AA}$ provides the opportunity to separate these individual contributions and identify QGP signatures in small systems. Predictions for $R_{AA}^h$, $R_{AA}^D$, $R_{AA}^B$ in O-O collisions at $\sqrt{s}=7$ TeV are presented with and without the formation of a QGP and contrasted with the corresponding $R_{p(d)A}$ calculations. Upcoming single-hadron measurements at the LHC will not only test the O-O predictions for both light and heavy flavor production, but will shed light on the possibly very different dynamics of $p$-A and A-A reactions at similar soft particle production multiplicities.

    hep-phnucl-thPRC(2023)·38 citations
15. 15*

    Freezing Out Fluctuations in Hydro+ Near the QCD Critical Point

    Maneesha Pradeep🇺🇸 · Krishna Rajagopal🇺🇸 · Mikhail Stephanov🇺🇸 · Yi Yin🇨🇳

    We introduce a freeze-out procedure to convert the critical fluctuations in a droplet of quark-gluon plasma (QGP) that has, as it expanded and cooled, passed close to a posited critical point on the phase diagram into cumulants of hadron multiplicities that can subsequently be measured. The procedure connects the out-of-equilibrium critical fluctuations described in concert with the hydrodynamic evolution of the droplet of QGP by extended hydrodynamics, known as Hydro+, with the subsequent kinetic description in terms of observable hadrons. We introduce a critical scalar isoscalar field sigma whose fluctuations cause correlations between observed hadrons due to the couplings of the sigma field to the hadrons via their masses. We match the QGP fluctuations obtained by solving the Hydro+ equations describing the evolution of critical fluctuations before freeze-out to the correlations of the sigma field. In turn, these are imprinted onto correlations and fluctuations in the multiplicity of hadrons, most importantly protons, after freeze-out via the generalization of the familiar half-century-old Cooper-Frye freeze-out prescription which we introduce. The proposed framework allows us to study the effects of critical slowing down and the consequent deviation of the observable predictions from equilibrium expectations quantitatively. We also quantify the suppression of cumulants due to conservation of baryon number. We demonstrate the procedure in practice by freezing out a Hydro+ simulation in an azimuthally symmetric and boost invariant background that includes radial flow discussed in arXiv:1908.08539.

    hep-phnucl-thPRD(2022)·55 citations
16. 16*

    Geometrising the Micro-Cosmos on a Supermanifold

    Kieran Finn🇬🇧 · Viola Gattus🇬🇧 · Sotirios Karamitsos🇮🇹 · Apostolos Pilaftsis🇬🇧

    For more than half a century, covariant and differential geometric methods have been playing a central role in the development of Quantum Field Theory (QFT). After a brief historic overview of the major scientific achievements using these methods, we will focus on the covariant and differential geometric formalism originally proposed by Vilkovisky and DeWitt (VDW). We discuss recent developments made in addressing the uniqueness of the path-integral measure of the VDW effective action, and so address the problem of quantum frame dependence in cosmologically relevant scalar-tensor theories beyond the classical approximation. Particular attention will be drawn to a long-standing problem concerning the obstacles that the VDW formalism was facing from its original conception in describing generic QFTs that include fermions. We show how in addition to bosons the VDW effective action can be extended to supermanifolds to include fermions. The so-extended formulation appears to be very promising for a complete geometrisation of realistic theories of micro-cosmos, such as the Standard Model and its gravitational sector.

    ↳ hep-thhep-phPoS(2022)·10 citations
17. 17*

    Nonperturbative Determination of Collins-Soper Kernel from Quasi Transverse-Momentum Dependent Wave Functions

    Min-Huan Chu🇨🇳 · Zhi-Fu Deng🇨🇳 · Jun Hua🇨🇳 · Xiangdong Ji🇺🇸 · Andreas Schäfer🇩🇪 · Yushan Su🇺🇸 · Peng Sun🇨🇳 · Wei Wang🇨🇳 · Yi-Bo Yang🇨🇳 · Jun Zeng🇨🇳 · Jialu Zhang🇨🇳 · Jian-Hui Zhang🇨🇳 · Qi-An Zhang🇨🇳

    In the framework of large-momentum effective theory at one-loop matching accuracy, we perform a lattice calculation of the Collins-Soper kernel which governs the rapidity evolution of transverse-momentum-dependent (TMD) distributions. We first obtain the quasi TMD wave functions at three different meson momenta on a lattice with valence clover quarks on a dynamical HISQ sea and lattice spacing $a=0.12$~fm from MILC, and renormalize the pertinent linear divergences using Wilson loops. Through one-loop matching to the light-cone wave functions, we determine the Collins-Soper kernel with transverse separation up to 0.6~fm. We study the systematic uncertainties from operator mixing and scale dependence, as well as the impact from higher power corrections. Our results potentially allow for a determination of the soft function and other transverse-momentum dependent quantities at one-loop accuracy.

    ↳ hep-lathep-phPRD(2022)·103 citations
18. 18*

    Production and anisotropic flow of thermal photons in collision of $\alpha$-clustered carbon with heavy nuclei at relativistic energies

    Pingal Dasgupta🇨🇳 · Rupa Chatterjee🇮🇳 · Guo-Liang Ma🇨🇳

    The presence of $\alpha$-clustered structure in the light nuclei produces different exotic shapes in nuclear structure studies at low energies. Recent phenomenological studies suggest that collision of heavy nuclei with $\alpha$-clustered carbon (${}^{12}$C) at relativistic energies can lead to large initial state anisotropies. This is expected to impact the final momentum anisotropies of the produced particles significantly. The emission of electromagnetic radiations is considered to be more sensitive to the initial state compared to hadronic observables and thus photon observables are expected to be affected by the initial clustered structure profoundly. In this work we estimate the production and anisotropic flow of photons from most-central collisions of triangular $\alpha$-clustered carbon and gold at $\sqrt{s_{\mathrm{NN}}}=200$ GeV using an event-by-event hydrodynamic framework and compare the results with those obtained from unclustered carbon and gold collisions. We show that the thermal photon $v_3$ for most central collisions is significantly large for the clustered case compared to the case with unclustered carbon, whereas the elliptic flow parameter does not show much difference for the two cases. In addition, the ratio of anisotropic flow coefficients is found to be a potential observable to constrain the initial state produced in relativistic heavy-ion collisions and also to know more about the $\alpha$-clustered structure in carbon nucleus.

    ↳ nucl-thhep-phnucl-exPRC(2023)·10 citations
19. 19*

    Zero-temperature thermodynamics of dense asymmetric strong-interaction matter

    Jens Braun🇩🇪 · Benedikt Schallmo🇩🇪

    Employing constraints derived from the microscopic theory of the strong interaction, we estimate the zero-temperature phase structure of dense isospin-asymmetric matter with two quark flavors. We find indications that strong-interaction matter along trajectories relevant for astrophysical applications undergoes a first-order phase transition from a color-superconducting phase to an ungapped quark-matter phase when the density is increased. Such a phase transition is found to be absent in isospin-symmetric matter. Moreover, by taking into account constraints from $\beta$-equilibrium, charge neutrality, and color neutrality, we provide an estimate for the speed of sound in neutron-star matter. Notably, we observe that the speed of sound in neutron-star matter exceeds the asymptotic value associated with the noninteracting quark gas and even increases towards lower densities across a wide range, in agreement with recent results for isospin-symmetric matter. Considering results from studies based on chiral effective field theory at low densities, our findings suggest the existence of a maximum in the speed of sound for $n/n_0\lesssim 10$, where $n_0$ is the nuclear saturation density.

    ↳ nucl-thhep-phPRD(2022)·37 citations
20. 20*

    General relativity effects in precision spin experimental tests of fundamental symmetries

    Sergey N. Vergeles · Nikolai N. Nikolaev · Yuri N. Obukhov · Alexander J. Silenko · Oleg V. Teryaev

    A search for the $P$- and $CP(T)$-violating electric dipole moments (EDM) of atoms, particles and nuclei with sensitivity up to $10^{-15}$ in units of magnetic dipole moments, allowed by all discrete symmetries, is one of the topical problems of modern physics. According to Sakharov, $CP$-violation is one of the three key criteria of baryogenesis in generally accepted paradigm of the Big Bang cosmology. All three criteria are supported by the Standard Model (SM), but it fails to describe the observed baryon asymmetry of the Universe. This is regarded a strong argument in favor of existence of $CP$-symmetry breaking mechanisms beyond minimal SM, which can lead to measurable EDMs of atoms, particles and nuclei. Direct searches for EDM of charged particles and nuclei are possible only in storage rings (COSY, NICA). After successful studies by the JEDI collaboration at the COSY synchrotron, at the forefront is a search for the proton EDM in an electrostatic storage ring with the proton spin frozen at the magic energy with projected sensitivity $d_p\sim 10^{-29}e\cdot$cm. Following a brief introduction to the $CP$-violation physics and the baryogenesis, the review presents a detailed discussion of significant contributions to the spin dynamics from the terrestrial gravity along with the new effects of Earth's rotation in ultrasensitive searches for the EDM of charged particles and neutrons. Quite remarkably, for the projected sensitivity to the proton EDM, these false EDM effects can by one to two orders of magnitude exceed the signal of the proton EDM, and become comparable to an EDM contribution in experiments with ultracold neutrons. We also discuss the role of a precessing spin as a detector of the axion-like dark matter, and consider applications of the quantum gravitational anomalies to the dense matter hydrodynamics and the spin phenomena in the non-central nuclear collisions.

    ↳ hep-thgr-qchep-phnucl-th+1Usp.Fiz.Nauk(2023)·32 citations
21. 21*

    The Andromeda Gamma-Ray Excess: Background Systematics of the Millisecond Pulsars and Dark Matter Interpretations

    Fabian Zimmer🇳🇱 · Oscar Macias🇳🇱 · Shin'ichiro Ando🇳🇱 · Roland M. Crocker🇦🇺 · Shunsaku Horiuchi🇺🇸

    Since the discovery of an excess in gamma rays in the direction of M31, its cause has been unclear. Published interpretations focus on a dark matter or stellar related origin. Studies of a similar excess in the Milky Way center motivate a correlation of the spatial morphology of the signal with the distribution of stellar mass in M31. However, a robust determination of the best theory for the observed excess emission is very challenging due to large uncertainties in the astrophysical gamma-ray foreground model. Here we perform a spectro-morphological analysis of the M31 gamma-ray excess using state-of-the-art templates for the distribution of stellar mass in M31 and novel astrophysical foreground models for its sky region. We construct maps for the old stellar populations of M31 based on observational data from the PAndAS survey and carefully remove the foreground stars. We also produce improved astrophysical foreground models by using novel image inpainting techniques based on machine learning methods. We find that our stellar maps, taken as a proxy for the location of a putative population of millisecond pulsars in the bulge of M31, reach a statistical significance of $5.4\sigma$, making them as strongly favoured as the simple phenomenological models usually considered in the literature, e.g., a disk-like template with uniform brightness. Our detection of the stellar templates is robust to generous variations of the astrophysical foreground model. Once the stellar templates are included in the astrophysical model, we show that the dark matter annihilation interpretation of the signal is unwarranted. Using the results of a binary population synthesis model we demonstrate that a population of about one million unresolved MSPs could naturally explain the observed gamma-ray luminosity per stellar mass, energy spectrum, and stellar bulge-to-disk flux ratio.

    ↳ astro-ph.HEhep-phMNRAS(2022)·13 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.