Mon·Aug 26, 2024Monday·August 26, 2024

1. 01*

   Gravitationally Misaligned Ultralight Dark Matter and Implications for Neutron Stars

   Hooman Davoudiasl🇺🇸

   We examine the possibility that dark matter (DM) may be an ultralight scalar that was misaligned via non-minimal coupling to gravity, in the early Universe. For a certain regime of scalar masses, gravitational effects in neutron stars could place interesting bounds on the viable parameter space of the model, even in the absence of non-gravitational interactions between DM and ordinary matter.

   hep-phastro-ph.COPRD(2024)·5 citations
2. 02*

   Analytic amplitudes for a pair of Higgs bosons in association with three partons

   John M. Campbell🇺🇸 · Giuseppe De Laurentis🇬🇧 · R. Keith Ellis🇬🇧

   The pair production of Higgs bosons at the LHC can give information about the triple Higgs boson coupling. We perform an analytic one-loop calculation of the amplitudes for a pair of Higgs bosons in association with three partons, retaining the exact dependence on the quark mass circulating in the loop. These amplitudes constitute the real radiation corrections in the calculation of Higgs boson pair production at next-to-leading order in the strong coupling. The results of an analytic generalised-unitarity computation are simplified via analytic reconstruction in spinor variables. Compact ansätze for kinematic pole residues are iteratively fitted via $p$-adic evaluations near said poles and subtracted until no pole remains. A new ansatz construction is introduced to minimally parametrise coefficients of amplitudes with multiple massive external legs. The simplified expressions are faster to evaluate than automatic codes and can lead to more stable results near singular regions.

   hep-phJHEP(2024)·12 citations
3. 03*

   The photon parton distribution function: updates and applications

   Aneesh Manohar🇺🇸 · Paolo Nason🇮🇹 · Gavin Salam🇬🇧 · Giulia Zanderighi🇩🇪

   The photon parton distribution function (PDF) of the proton is crucial for precise comparisons of LHC cross sections with theoretical predictions. However, it was previously affected by very large uncertainties of around $\mathcal{O}(100\%)$ or dependent upon phenomenologically inspired models. In the paper~\cite{Manohar:2016nzj}, we demonstrated how the photon PDF could be determined using the proton structure functions $F_2$ and $F_L$ measured in electron--proton scattering experiments. We provided an explicit formula for the PDF, which can be systematically improved order by order in perturbation theory. We obtained a photon PDF with errors $\lesssim 2$\% for $10^{-4}<x<0.1$. Here, we recall the underlying idea and method used to obtain this result, as well as the progress made since then.

   hep-ph1 citation
4. 04*

   Improved precision on 2-3 oscillation parameters using the synergy between DUNE and T2HK

   Sanjib Kumar Agarwalla🇮🇳 · Ritam Kundu🇮🇳 · Masoom Singh🇮🇳

   A high-precision measurement of $\Delta m_{31}^2$ and ${\theta }_{23}$ is inevitable to estimate the Earth's matter effect in long-baseline experiments which in turn plays an important role in addressing the issue of neutrino mass ordering and to measure the value of CP phase in $3\nu$ framework. After reviewing the results from the past and present experiments, and discussing the near-future sensitivities from the IceCube Upgrade and KM3NeT/ORCA, we study the expected improvements in the precision of 2-3 oscillation parameters that the next-generation long-baseline experiments, DUNE and T2HK, can bring either in isolation or combination. We highlight the relevance of the possible complementarities between these two experiments in obtaining the improved sensitivities in determining the deviation from maximal mixing of ${\theta }_{23}$, excluding the wrong-octant solution of ${\theta }_{23}$, and obtaining high precision on 2-3 oscillation parameters, as compared to their individual performances. We observe that for the current best-fit values of the oscillation parameters and assuming normal mass ordering (NMO), DUNE + T2HK can establish the non-maximal ${\theta }_{23}$ and exclude the wrong octant solution of ${\theta }_{23}$ at around 7$\sigma$ C.L. with their nominal exposures. We find that DUNE + T2HK can improve the current relative 1$\sigma$ precision on ${\sin }^2{\theta }_{23}(\Delta m_{31}^2)$ by a factor of 7 (5) assuming NMO. Also, we notice that with less than half of their nominal exposures, the combination of DUNE and T2HK can achieve the sensitivities that are expected from these individual experiments using their full exposures. We also portray how the synergy between DUNE and T2HK can provide better constraints on (${\sin }^2{\theta }_{23}$ - ${\delta }_{\mathrm{CP}}$) plane as compared to their individual reach.

   hep-phhep-exphysics.ins-detJHEP(2024)·6 citations
5. 05*

   Spectroscopic Analysis of Singly Heavy Pentaquarks in the Symmetric 15-Plet Representation Using Phenomenological Models

   Ankush Sharma🇮🇳 · Alka Upadhyay🇮🇳

   We analyze the ground state pentaquark structures with a single heavy quark ($qqqq\text{Bar}Q$) using various phenomenological models. The recent observations of singly heavy tetraquark structures at LHCb serve as a significant motivation for this investigation. We studied the symmetric 15-plet configuration of SU(3) flavor representation with the spin-parity assignment of $5/2^{-}$, representing the symmetric spin state for the pentaquark systems. We employed an extended Gursey-Radicati mass formula and an effective mass scheme to compute the mass spectra of pentaquark states. Additionally, the methodology of the screened charge scheme is introduced to calculate the magnetic moment assignments, specifically for configurations involving both charm and bottom quarks. We also proposed the potential production modes originating from the weak decay of heavy baryons. We identified the strong decay channels where pentaquark transitions into a light baryon and a heavy meson. Our analysis of mass spectra, magnetic moments, and possible strong decay channels helps us to explore the inner structure of pentaquarks and their underlying quark dynamics. This work not only augments the theoretical frameworks used to describe such systems but is also helpful for future experimental pursuits at facilities like LHCb, fostering further experimental validations and discoveries in heavy quark spectroscopy.

   hep-phEur.Phys.J.Plus(2025)·5 citations
6. 06*

   Production of single isolated photons in the Parton Reggeization Approach

   Alexey Chernyshev🇷🇺 · Vladimir Saleev🇷🇺

   In the article, we study the processes of single isolated photon production at the LHC energies in the framework of the Parton Reggeization Approach taking into account LO and NLO* contributions, the last one includes only tree-level corrections. Reggeized amplitudes are constructed according to the effective field theory formalism for multi-Regge kinematics processes suggested by L.N. Lipatov. To avoid the double counting between tree-level corrections and unintegrated parton distribution functions, a subtraction scheme is introduced. The results of calculations are compared with experimental data.

   hep-phPhys.Part.Nucl.Lett.(2023)·0 citations
7. 07*

   A study of systematic uncertainties within the MSHT PDF Framework

   Matthew Reader🇬🇧

   Experimental errors are now incredibly precise, and are often dominated by the systematic uncertainties. Therefore the errors obtained in the Parton Distribution Functions that are extracted from this data will also be dominated by these experimental systematic errors, as well as the systematic errors embedded in the theoretical calculations. However, as is well known, there are often significant uncertainties in these systematic errors, and so to determine precisely the errors in the Parton Distribution Functions, we need to be thoughtful about the uncertainties in the errors themselves. In this paper, we discuss an approach where these "errors on errors" can be incorporated into a ${\chi }^2$ calculation, and investigate how such a model behaves and what it tells us about the resulting errors. Also we look at two data sets, ATLAS W,Z Data [arXiv:1612.03016] and the ATLAS 7 TeV Inclusive Jet Distribution Data [arXiv:1410.8857] and investigate the information that this model implies about these two data sets.

   hep-phhep-exPoS(2025)·3 citations
8. 08*

   Search for the $\Sigma (1380)1/2^{-}$ state in ${\Lambda }_c^{+}\to \gamma {\pi }^{+}\Lambda$ decay by triangle singularity

   Ke Wang🇨🇳 · Yu-Fei Wang🇨🇳 · Bo-Chao Liu🇨🇳 · Fei Huang🇨🇳

   In this work, we investigate the resonance production in ${\Lambda }_c^{+}\to \gamma {\pi }^{+}\Lambda$ decay through the triangle singularity (TS) mechanism, within an effective Lagrangian approach. We find that the appropriate loop decay process could develop a triangle singularity in the invariant mass $M_{\pi \Lambda }$ around $1.35$ GeV, with the shape depending on the quantum numbers of ${\Sigma }^{\ast }$ states that couple to the final $\pi \Lambda$ system. Especially, the $\Sigma (1380)1/2^{-}$ state newly predicted in the pentaquark model, if exists, significantly enhances the TS contribution and sharpens the TS peak due to the $S$-wave ${\Sigma }^{\ast }\pi \Sigma$ vertex in the loop. Therefore, the existence of the $\Sigma (1380)1/2^{-}$ state can be examined by measuring the TS signal in ${\Lambda }_c^{+}\to \gamma {\pi }^{+}\Lambda$. Considering also possible tree-level diagrams, we additionally obtain the branching ratio $\mathrm{Br}({\Lambda }_c^{+}\to \gamma {\pi }^{+}\Lambda )\simeq 1.5\times 10^{-5}$. We suggest the investigation of this reaction by future BESIII, LHCb, and Belle experiments.

   hep-phnucl-thPRD(2024)·9 citations
9. 09*

   Exploring observable effects of scalar operators beyond SMEFT in the angular distribution of $B\to K^{\ast 0}{\tau }^{+}{\tau }^{-}$

   Siddhartha Karmakar🇮🇳 · Amol Dighe🇮🇳

   The $SU(2{)}_L\times U(1{)}_Y$ invariance of the Standard Model Effective Field Theory (SMEFT) imposes relations among different low-energy effective field theory Wilson coefficients (WCs), any deviations from which would signal the presence of physics beyond SMEFT. In this work, we investigate two such relations ($C_S=-C_P$, $C_S^{\prime }=C_P^{\prime }$) among the scalar and the pseudoscalar new-physics WCs that can contribute to $b\to s\tau \tau$ processes. We show that, even when new physics violating these relations would not be measurable in the branching ratios of $B_s\to {\tau }^{+}{\tau }^{-}$ and $B\to K^{(\ast )}{\tau }^{+}{\tau }^{-}$ at HL-LHC and FCC-ee, it can still manifest itself in the angular distribution of $B\to K^{\ast 0}{\tau }^{+}{\tau }^{-}$. We identify the combinations of angular observables in this decay channel that are sensitive to scenarios beyond SMEFT. We find that the two observables $S_6^c$ and $A_7$, and their combination, have the potential to identify physics beyond SMEFT.

   hep-phPRD(2024)·3 citations
10. 10*

    Analysis of the resonance X(4630) at non-zero temperature

    G. Bozkır🇹🇷

    We calculate the spectroscopic parameters of resonance $X(4630)$ observed in the process $B^{+}\to J/\Psi \varphi K^{+}$ by at the LHCb experiments at CERN by means of thermal QCD sum rule method at non-zero temperature. The exotic vector $X(4630)$ is assigned as the diquark-antidiquark state $[cs][\overline{cs}]$ with spin-parity $J^{PC}=1^{-+}$. Employing the two-point QCD sum rule approach up to the sixth order of the operator dimension by including non-perturbative contribution, we calculate the mass and decay constant of $X(4630)$ at $T\ne 0$. The numerical analyses demonstrate that the values of the mass and decay constant of $X(4630)$ near the deconfinement temperature decrease up to $9.8\%$ and $60\%$ of their vacuum values. At $T\to 0$, the obtained results for the mass $m_{X(4630)}=(4649\pm 40)$ MeV and decay constant ${\lambda }_{X(4630)}=(10.07\pm 0.8)\times 10^{-3}$ MeV are in excellent agreement with the results reported by LHCb experiments and other theoretical predictions.

    hep-phhep-exhep-latEPJA(2024)·0 citations
11. 11*

    Exact two-loop amplitudes for Higgs plus jet production with a cubic Higgs self-coupling

    Ulrich Haisch🇩🇪 · Marco Niggetiedt🇩🇪

    We compute the corrections to the two-loop amplitudes for $gg\to h$, $gg\to hg$, $qg\to hq$, and $q\bar{q}\to hg$ due to a modified cubic Higgs self-coupling. The exact dependence on the Higgs and top-quark masses across the entire $2\to 2$ phase space is determined by numerically solving a system of differential equations for the relevant master integrals. The calculated amplitudes are crucial for evaluating the impact of the considered corrections on exclusive $pp\to hj$ production at the hadronic event level. As an application, we calculate the non-universal, kinematic-dependent cubic Higgs self-coupling corrections to the Higgs-boson transverse momentum distribution in gluon-gluon fusion Higgs production for arbitrary values of the transverse momentum.

    hep-phhep-exJHEP(2024)·16 citations
12. 12*

    On the impact of the mixed $Z/\gamma$ PDF at muon colliders

    David Marzocca🇮🇹 · Alfredo Stanzione🇮🇹

    We study the role of the $Z/\gamma$-interference parton distribution function (PDF) in high-energy muon colliders. We review how this PDF emerges when electroweak interactions are applied to the collinear splitting process and show that the leading-order approximation is significantly suppressed due to an accidental cancellation. However, this suppression does not appear in the leading-logarithm resummed numerical result, where the $Z/\gamma$ PDF is instead comparable to those of other electroweak gauge bosons. By extending the analytical approximation to next-to-leading order, we show the mechanism by which the suppression is lifted and provide a more accurate approximation to the numerical result. Furthermore, we explore the impact of the $Z/\gamma$ PDF in several processes at future muon colliders. High-energy Compton scattering is identified as a promising process for observing experimentally this peculiar electroweak effect with high precision. We also quantify the impact of the $Z/\gamma$ PDF on Higgs physics and, as a new physics example, in resonant single-production of axion-like particles (ALP).

    hep-phJHEP(2025)·11 citations
13. 13*

    Non-unitary limits on different textures for low-scale seesaw models

    Jesús Miguel Celestino-Ramírez🇲🇽 · G. Hernández-Tomé🇲🇽 · O. G. Miranda🇲🇽 · Eduardo Peinado🇲🇽

    New heavy neutral leptons lead to non-unitary effects in models for neutrino masses. Such effects could represent a sign of new physics beyond the Standard Model, leading to observable deviations in neutrino oscillation experiments, lepton flavor violation, and other precision measurements. This work explores the parameter space of the linear and inverse low-scale seesaw models based on flavor symmetries consistent with neutrino oscillation experiments. In particular, we investigated the violation of unitarity when the lepton flavor violation is absent and when only one lepton flavor-violating channel is present.

    hep-phEPJC(2025)·3 citations
14. 14*

    Jet veto resummation for STXS $H+$1-jet bins at aNNLL${}^{\prime }$+NNLO

    Pedro Cal🇩🇪 · Matthew A. Lim🇬🇧 · Darren J. Scott🇩🇪 · Frank J. Tackmann🇩🇪 · Wouter J. Waalewijn🇳🇱

    Measurements of Higgs boson processes by the ATLAS and CMS experiments at the LHC use Simplified Template Cross Sections (STXS) as a common framework for the combination of measurements in different decay channels and their further interpretation, e.g. to measure Higgs couplings. The different Higgs production processes are measured in predefined kinematic regions -- the STXS bins -- requiring precise theory predictions for each individual bin. In gluon-fusion Higgs production a main division is into 0-jet, 1-jet, and $\ge 2$-jet bins, which are further subdivided in bins of the Higgs transverse momentum $p_T^H$. Requiring a fixed number of jets induces logarithms $\ln p_T^{\mathrm{cut}}/Q$ in the cross section where $p_T^{\mathrm{cut}}$ is the jet-$p_T$ threshold and $Q\sim p_T^H\sim m_H$ the hard-interaction scale. These jet-veto logarithms can be resummed to all orders in perturbation theory to achieve the highest possible perturbative precision. We provide state-of-the art predictions for the $p_T^H$ spectrum in exclusive $H+$1-jet production and the corresponding $H+$1-jet STXS bins in the kinematic regime $p_T^{\mathrm{cut}}\ll p_T^H\sim m_H$. We carry out the resummation at NNLL${}^{\prime }$ accuracy, using theory nuisance parameters to account for the few unknown ingredients at this order, and match to full NNLO. We revisit the jet-veto factorization for this process and find that it requires refactorizing the total soft function into a global and soft-collinear contribution in order to fully account for logarithms of the signal jet radius. The leading nonglobal logarithms are also included, though they are numerically small for the region of phenomenological interest.

    hep-phhep-exJHEP(2025)·9 citations
15. 15*

    A Field-Theory Action for the Constructive Standard Model

    Neil Christensen🇺🇸

    We introduce a field-theory framework in which fields transform under the little group, rather than the Lorentz group, specific to each particle type. By utilizing these fields, along with spinor products and the x factor, we construct a field-theory action that naturally reproduces the vertices of the Constructive Standard Model (CSM). This approach eliminates unphysical components, significantly reduces the degrees of freedom compared to traditional field theory, and offers deeper insights into the power of constructive amplitudes. Our action is momentum-conserving, Lorentz-invariant, Hermitian, and non-local. We also discuss this as a framework for developing new constructive field theories, discussing their essential properties and potential applicability in renormalization theory and non-perturbative calculations.

    hep-phhep-thPRD(2024)·3 citations
16. 16*

    Phenomenology of Electroweak Portal Dark Showers: High Energy Direct Probes and Low Energy Complementarity

    Hsin-Chia Cheng🇺🇸 · Xu-Hui Jiang🇨🇳 · Lingfeng Li🇺🇸

    We investigate the phenomenology of a dark QCD sector interacting with the Standard Model (SM) via the electroweak (EW) portals. The portal interactions allow SM bosons, such as $Z$ and $h$, or additional bosons that mix with them, to decay into dark quarks, producing dark showers. The light dark mesons are expected to be long-lived particles (LLPs), as their decays back to the SM states through the EW-portal interactions typically have macroscopic decay lengths. We focus on dark shower events initiated by various bosons at the Large Hadron Collider (LHC). The most prominent signal is the displaced decay of GeV-scale dark pions as LLPs. Current limits on dark shower signals at LHC detectors are recast from public data in a model-independent manner. Future limits in the high-luminosity phase and proposed auxiliary detectors are also projected. Additionally, we study the flavor-changing neutral current (FCNC) $B$ decays into dark pions, obtaining both current and projected constraints at the LHC and other facilities. These constraints can be combined for specific models, which are illustrated in two EW-portal benchmarks: one with the heavy doublet fermion mediation and another with the $Z^{\prime }$ mediator including a mass mixing. The collider reach shows significant potential to probe the parameter space unconstrained by EW precision tests, highlighting the necessity of dedicated LLP search strategies and facilities.

    hep-phhep-exJHEP(2025)·14 citations
17. 17*

    Ultraheavy Dark Matter and WIMPs Production aided by Primordial Black Holes

    Giorgio Arcadi🇮🇹 · Manfred Lindner🇩🇪 · Jacinto P. Neto🇧🇷 · Farinaldo S. Queiroz🇧🇷

    The unitary bound restricts thermal relics to be lighter than $100$ TeV. This work investigates the production of ultraheavy dark matter and WIMPs in the presence of primordial black holes. Firstly, we describe how Hawking evaporation can produce ultraheavy dark matter with masses above $10^{12}$ GeV in radiation and matter-domination eras. Later, we assess how primordial black holes that induce a non-standard cosmology impact the predicted relic density of a thermal relic and explore the interplay between them, considering the restrictions arising from entropy injection due to the evaporation of primordial black holes. Considering a concrete B-L model, where the dark matter is a Dirac particle, we obtain the correct relic density for various freeze-out scenarios and show that a dark matter particle can nicely reproduce the correct relic density in agreement with current limits with masses above the $10$ TeV scale. Hence, this work strengthens the continuous search for heavy dark matter particles.

    hep-phhep-th8 citations
18. 18*

    Parton Distribution Function of a Deuteron-like Dibaryon System from Lattice QCD

    Chen Chen🇨🇳 · Liuming Liu🇨🇳 · Peng Sun🇨🇳 · Yi-Bo Yang🇨🇳 · Yiqi Geng🇨🇳 · Fei Yao🇨🇳 · Jian-Hui Zhang · Kuan Zhang

    We report a lattice QCD calculation of the parton distribution function (PDF) of a deuteron-like dibaryon system using large-momentum effective theory. The calculation is done on three Wilson Clover ensembles with a fixed lattice spacing a=0.105 fm and two pion masses. The lattice matrix elements are computed at proton momenta up to 2.46 GeV with the signal of high momentum modes being improved by applying the momentum smearing technique. The state-of-the-art renormalization, matching and extrapolation are then applied to obtain the final result of the light-cone PDF. A comparison between the result of the dibaryon system and the sum of the proton and neutron PDFs is also given.

    ↳ hep-lathep-phnucl-thPRD(2025)·21 citations
19. 19*

    Quarkyonic equation of state with a momentum dependent interaction and neutron star structure

    K. Folias🇬🇷 · Ch.C. Moustakidis🇬🇷

    The structure and basic properties of dense nuclear matter still remain one of the open problems of Physics. In particular, the composition of the matter that composes neutron stars is under theoretical and experimental investigation. Among the theories that have been proposed, apart from the classical one where the composition is dominated by hadrons, the existence or coexistence of free quark matter is a dominant guess. An approach towards this solution is the phenomenological view according to which the existence of quarkyonic matter plays a dominant role in the construction of the equation of state (EOS). According to it the structure of the EOS is based on the existence of the quarkyonic particle which is a hybrid state of a particle that combines properties of hadronic and quark matter with a corresponding representation in momentum space. In this paper we propose a phenomenological model for quarkyonic matter, borrowed from corresponding applications in hadronic models, where the interaction in the quarkyonic matter depends not only on the position but also on the momentum of the quarkyonic particles. This consideration, as we demonstrate, can have a remarkable consequence on the shape of the EOS and thus on the properties of neutron stars, offering a sufficiently flexible model. Comparison with recent observational data can place constraints on the parameterization of the particular model and help improve its reliability.

    ↳ nucl-thastro-ph.HEhep-phNPA(2025)·7 citations
20. 20*

    S-Matrix Bootstrap and Non-Invertible Symmetries

    Christian Copetti🇬🇧 · Lucia Cordova🇨🇭 · Shota Komatsu🇨🇭

    We initiate the S-matrix bootstrap analysis of theories with non-invertible symmetries in (1+1) dimensions. Our previous work showed that crossing symmetry of S-matrices in such theories is modified, with modification characterized by the fusion category data. By imposing unitarity, symmetry and the modified crossing, we constrain the space of consistent S-matrices, identifying integrable theories with non-invertible symmetries at the cusps of allowed regions. We also extend the modified crossing rules to cases where vacua transform in non-regular representations of fusion category, utilizing a connection to a dual category ${\mathcal{C}}_{\mathcal{M}}^{\ast }$ and Symmetry Topological Field Theory (SymTFT). This highlights the utility of SymTFT in the analysis of scattering amplitudes.

    ↳ hep-thcond-mat.str-elhep-phJHEP(2025)·58 citations
21. 21*

    Renormalization and running in the 2D $CP(1)$ model

    Diego Buccio🇮🇹 · John F. Donoghue🇺🇸 · Gabriel Menezes🇧🇷 · Roberto Percacci🇮🇹

    We calculate the scattering amplitude in the two dimensional $CP(1)$ model in a regularization scheme independent way. When using cutoff regularization, a new Feynman rule from the path integral measure is required if one is to preserve the symmetry. The physical running of the coupling with renormalization scale arises from a UV finite Feynman integral in all schemes. We reproduce the usual result with asymptotic freedom, but the pathway to obtaining the beta function can be different in different schemes. We also comment on the way that this model evades the classic argument by Landau against asymptotic freedom in non-gauge theories.

    ↳ hep-thhep-phJHEP(2025)·4 citations
22. 22*

    Spatial imaging of polarized deuterons at the Electron-Ion Collider

    Heikki Mäntysaari🇫🇮 · Farid Salazar🇺🇸 · Björn Schenke🇺🇸 · Chun Shen🇺🇸 · Wenbin Zhao🇺🇸

    We study diffractive vector meson production at small-$x$ in the collision of electrons and polarized deuterons $e+d^{\uparrow }$. We consider the polarization dependence of the nuclear wave function of the deuteron, which results in an azimuthal angular dependence of the produced vector meson when the deuteron is transversely polarized. The Fourier coefficients extracted from the azimuthal angular dependence of the vector meson differential cross-section exhibit notable differences between longitudinally and transversely polarized deuterons. The angular dependence of the extracted effective deuteron radius provides direct insight into the structure of the polarized deuteron wave function. Furthermore, we observe slightly increased gluon saturation effects when the deuteron is longitudinally polarized compared to the transversely polarized case. The small-$x$ observables studied in this work will be accessible at the future Electron-Ion Collider.

    ↳ nucl-thhep-phnucl-exPLB(2024)·8 citations
23. 23*

    Vertex correction to nuclear matrix elements of double-$\beta$ decays

    Jun Terasaki🇨🇿

    The predicted neutrinoless double-$\beta$ ($0\nu \beta \beta$) decay is the crucial phenomenon to prove the existence of the Majorana neutrino, which gives a foundation to leptogenesis to explain the matter prevalence of the universe. The nuclear matrix element (NME) of $0\nu \beta \beta$ decay is an important theoretical quantity to determine the effective neutrino mass and help the detector design for the next generation of the $0\nu \beta \beta$ decay search. Reliable calculation of this NME is a long-standing problem because of the diversity of the predicted values of the NME. The main reason for this difficulty is that the effective strength of the Gamow-Teller transition operator $g_A$ for this decay is unknown. I will show the lowest-order vertex corrections for the $0\nu \beta \beta$ and the $2\nu \beta \beta$ NME of ${}^{136}$Xe in the framework of the hybrid application of the quantum field theory to the leptons and the Rayleigh-Schrödinger perturbation to the nucleus. The unperturbed nuclear states are obtained by the quasiparticle random-phase approximation. These corrections reduce the $0\nu \beta \beta$ NME by 30%. The effective $g_A$ referring to this reduced NME is also obtained, and it is shown for the first time that the effective $g_A$ for the $0\nu \beta \beta$ NME is not quite different from that for the $2\nu \beta \beta$ NME; the difference is only 10%. This indicates the possibility that the phenomenological effective $g_A$ to reproduce the experimental half-life of the $2\nu \beta \beta$ decay can be approximately used for the calculation of the $0\nu \beta \beta$ NME.

    ↳ nucl-thhep-phnucl-exPoS(2025)·0 citations
24. 24*

    CMB limits on decaying dark matter beyond the ionization threshold

    Clara Xu🇺🇸 · Wenzer Qin🇺🇸 · Tracy R. Slatyer🇺🇸

    The temperature and polarization anisotropies of the cosmic microwave background (CMB) have been used to set constraints on decaying dark matter models down to keV masses. In this work, we extend these limits down to the sub-keV mass range. Using principal component analysis, we estimate the lower bound on the decay lifetime for a basis of different dark matter masses and Standard Model final states, from which the bound on an arbitrary model can be calculated. We validate our principal component analysis using Markov chain Monte Carlo methods and Planck 2018 data. We perform a separate analysis for models decaying into photons below the hydrogen ionization threshold. We demonstrate that for these models, the effect of energy deposition can be captured approximately by a single parameter, but the redshift dependence of the effect is very different from higher-energy injections; in particular, the perturbations to CMB anisotropies are more sensitive to energy deposited around the time of recombination.

    ↳ astro-ph.COhep-phPRD(2024)·18 citations
25. 25*

    Can Baby Universe Absorption Explain Dark Energy?

    Varun Muralidharan🇨🇦 · James M. Cline🇨🇦

    It has been proposed that the accelerated expansion of the universe can be explained by the merging of our universe with baby universes, resulting in dark energy with a phantom-like equation of state. However, the evidence in favor of it did not include the full set of cosmological observables. Here we examine the implications of this model for both early and late universe cosmology using data from Planck collaboration, DESI 2024 and other experiments. We find that the pure baby universe model gives a poor fit to current data. Extending it to include a contribution from the cosmological constant, we find two allowed regions of parameter space: one close to $\Lambda$CDM, and another with $\Lambda <0$ plus the exotic dark energy component. The two regions can be significantly favored over $\Lambda$CDM, depending on the choice of supernova datasets, and they can ameliorate the Hubble tension to the level of $2\sigma$, depending on the supernova dataset. The model with $\Lambda <0$ features an equation of state $w(a)$ with a pole singularity at early times.

    ↳ astro-ph.COgr-qchep-phhep-thPRD(2025)·8 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.