Tue·Jul 4, 2023Tuesday·July 4, 2023

1. 01*

   TASI lectures on Phase Transitions, Baryogenesis, and Gravitational Waves

   Djuna Croon🇬🇧

   These lectures, presented at the 2022 TASI summer school, give an introductory overview of first-order phase transitions in the early Universe, baryogenesis, and the resulting gravitational wave phenomenology. We introduce thermal field theory via the imaginary time formalism, and comment on the pitfalls of 1-loop calculations and alternative approaches. Then, we discuss how to calculate the false vacuum decay rate in first order phase transitions, of which we give various examples in theories beyond the Standard Model. Baryogenesis is presented via the Sakharov conditions, and how they are met in important classes of examples. Finally, we explore gravitational waves from the early Universe, first reviewing the basics of gravitational wave generation and then focusing on the specific example of first order phase transitions.

   hep-phastro-ph.COPoS(2024)·27 citations
2. 02*

   Displaced Signals of Hidden Vectors at the Electron-Ion Collider

   Hooman Davoudiasl🇺🇸 · Roman Marcarelli🇺🇸 · Ethan T. Neil🇺🇸

   The Electron-Ion Collider (EIC) provides unique opportunities in searching for new physics through its high center of mass energy and coherent interactions of large nuclei. We examine how light weakly interacting vector bosons from a variety of models can be discovered or constrained, over significant parts of their parameter space, through clean displaced vertex signals at the EIC. Our results indicate that the searches we propose favorably compare with or surpass existing experimental projections for the models examined. The reach for the new physics that we consider can be markedly improved if "far backward" particle identification capabilities are included in the EIC detector complex.

   hep-phhep-exnucl-exPRD(2023)·19 citations
3. 03*

   Simplifying the large mass expansion

   V.A. Smirnov🇷🇺

   It is shown how the well-known large mass expansion can be simplified to obtain more terms of the expansion in an analytic form. Expanding two-loop four-point Feynman integrals which contribute to the process $H\to ggg$ is used as an example.

   hep-phhep-thTheor.Math.Phys.(2024)·5 citations
4. 04*

   Axion-Like Particles at future $e^{-}p$ collider

   Karabo Mosala🇿🇦 · Pramod Sharma🇮🇳 · Mukesh Kumar🇿🇦 · Ashok Goyal🇮🇳

   In this work, we explore the possibilities of producing Axion-Like Particles (ALPs) in a future $e^{-}p$ collider. Specifically, we focus on the proposed Large Hadron electron collider (LHeC), which can achieve a center-of-mass energy of $\sqrt{s}\approx 1.3$~TeV, enabling us to probe relatively high ALP masses with $m_a\lesssim 300$~GeV. The production of ALPs can occur through various channels, including $W^{+}{W}^{-}$, $\gamma \gamma$, $ZZ$, and $Z\gamma$-fusion within the collider environment. To investigate this, we conduct a comprehensive analysis that involves estimating the production cross section and constraining the limits on the associated couplings of ALPs, namely $g_{WW}$, $g_{\gamma \gamma }$, $g_{ZZ}$, and $g_{Z\gamma }$. To achieve this, we utilize a multiple-bin ${\chi }^2$ analysis on sensitive differential distributions. Through the analysis of these distributions, we determine upper bounds on the associated couplings within the mass range of 5~GeV $\le m_a\le$ 300~GeV. The obtained upper bounds are of the order of $\mathcal{O}(10^{-1})$ for $g_{\gamma \gamma }$ ($g_{WW}$, $g_{ZZ}$, $g_{Z\gamma }$) in $m_a\in$~[5, 200 (300)]~GeV considering an integrated luminosity of 1~ab${}^{-1}$. Furthermore, we compare the results of our study with those obtained from other available experiments. We emphasize the limits obtained through our analysis and showcase the potential of the LHeC in probing the properties of ALPs.

   hep-phEPJC(2024)·8 citations
5. 05*

   Dynamics of heavy flavour in a weakly magnetized hot QCD medium

   Debarshi Dey🇮🇳 · Binoy krishna Patra🇮🇳

   We obtain the spatial and momentum diffusion coefficients ($D_s$ and $\kappa$), and the collisional energy loss ($dE/dx$) of a heavy quark (HQ) traversing through a thermal medium of quarks and gluons in a weak magnetic field ($B$), for the two cases of the HQ moving either parallel or perpendicular to $\mathbf{B}$. For that purpose, we consider Coulomb scatterings ($t$-channel) of the HQ with the light quarks, obtained from the imaginary part of the HQ self-energy via the cutting rules. Both the normalised (by $T^3$) %\textit{momentum} diffusion coefficients, $\kappa$, as well as $dE/dx$, for charm quarks are larger than that for bottom quarks due to the larger mass of the latter. Also, the effect of $B$ is more feeble on the bottom quark, compared to the charm quark. Comparatively, the magnitudes of both $\kappa$ and $dE/dx$ are significantly smaller for the case of $\mathbf{v}\perp \mathbf{B}$. For both the cases, our results show that the momentum transfer between the HQ and the medium takes place preferentially along the direction of HQ velocity, thus leading to a significant increase in the momentum diffusion anisotropy, compared to $B=0$. We also calculate the (scaled) spatial diffusion coefficient, which we find to be independent of the heavy flavor mass and is almost unaffected by changes in $B$.

   hep-phnucl-thPRD(2024)·9 citations
6. 06*

   Decay widths and mass spectra of single bottom baryons

   H. García-Tecocoatzi🇮🇹 · A. Giachino🇵🇱 · A. Ramirez-Morales🇰🇷 · Ailier Rivero-Acosta🇲🇽 · E. Santopinto🇮🇹 · Carlos Alberto Vaquera-Araujo🇲🇽

   We develop a Hamiltonian model that incorporates the spin, spin-orbit, and isospin interactions to determine the masses of the ground states of single-bottom baryons and their excitations up to the $D$-wave. Furthermore, we calculate the strong decay widths of single-bottom baryons using the ${}^3{P}_0$ model. Our calculations consider final states comprising bottom baryon-(vector/pseudoscalar) meson pairs and (octet/decuplet) baryon-(pseudoscalar/vector) bottom meson pairs within a constituent quark model. In that respect, this is the most complete investigation which has ever been performed in the single bottom baryon sector so far. Additionally, we compute the electromagnetic decay widths from $P$-wave states to ground states. The electromagnetic decays become dominant in cases where the strong decays are suppressed. The experimental uncertainties are propagated to the model parameters using a Monte Carlo bootstrap method. Our quantum number assignments, as well as our mass and strong decay width predictions, are in reasonable agreement with the available data. We also provide the partial decay widths for each open flavor channel. Our predictions of mass spectra and decay widths provide valuable information for the experiments seeking to identify new bottom baryons and knowledge of possible decay channels can aid in their identification in the data. Therefore, our results will be able to guide future searches for the undiscovered single bottom baryons at LHCb, ATLAS, and CMS.

   hep-phPRD(2024)·22 citations
7. 07*

   Muon collider signatures for a $Z^{\prime }$ with a maximal $\mu -\tau$ coupling in $U(1{)}_{L_{\mu }-L_{\tau }}$

   Jin Sun🇰🇷 · Fei Huang🇨🇳 · Xiao-Gang He🇨🇳

   The gauged $U(1{)}_{L_{\mu }-L_{\tau }}$ model is a candidate model for explaining the muon g-2 anomaly because the $Z^{\prime }$ in the model has a natural normal coupling to muon. Due to other experimental data constraints the viable mass range for the usual $Z^{\prime }$ is constrained to be lower than a few hundred MeV. It has been shown that if the $Z^{\prime }$ has a maximal off-diagonal mixing, $(\bar{\mu }{\gamma }^{\mu }\tau +\bar{\tau }{\gamma }^{\mu }\mu )Z_{\mu }^{\prime }$, a large mass for $Z^{\prime }$ is possible. This class of models has a very interesting signature for detection, such as ${\mu }^{-}{\mu }^{+}\to {\tau }^{-}{\tau }^{+}$ pair, ${\mu }^{-}{\mu }^{+}\to {\mu }^{\pm }{\mu }^{\pm }{\tau }^{\mp }{\tau }^{\mp }$ at a muon collider. In this work we study in detail these processes. We find that the in the parameter space solving the muon g-2 anomaly, t-channel ${\tau }^{-}{\tau }^{+}$ pair production can easily be distinguished at more than 5$\sigma$ level from the s-channel production as that predicted in the standard model. The smoking gun signature of doubly same sign ${\mu }^{\pm }{\mu }^{\pm }+{\tau }^{\mp }{\tau }^{\mp }$ pairs production can have a 5$\sigma$ sensitivity, at a muon collider of 3 TeV with $\mathcal{O}$($f{b}^{-1}$) luminosity.

   hep-ph5 citations
8. 08*

   Exploring $T_{\psi \psi }$ tetraquark candidates in a coupled-channels formalism

   Pablo G. Ortega🇪🇸 · David R. Entem🇪🇸 · Francisco Fernández🇪🇸

   This study investigates the properties of the $T_{\psi \psi }$ tetraquark candidates within a coupled-channels calculation of the $c\bar{c}-c\bar{c}$ system, specifically focusing on the $J^P=0^{\pm }$, $1^{\pm }$, and $2^{\pm }$ sectors. The analysis includes various channels containing a $J/\psi$, ${\psi }^{\prime }$, ${\eta }_c$, and ${\eta }_c^{\prime }$ meson. By searching for poles in the scattering matrix, a total of 29 states in different $J^P$ sectors with masses ranging from 6.1 to 7.6 GeV/c${}^2$ are identified. The study further investigates the masses, widths and branching ratios of these states, leading to the identification of two potential candidates for the experimental $T_{\psi \psi }(6200)$ tetraquark, one candidate for $T_{\psi \psi }(6600)$, two for $T_{\psi \psi }(6700)$, four for $T_{\psi \psi }(6900)$, and three for $T_{\psi \psi }(7200)$ tetraquarks. Additionally, the paper discusses strategies to discriminate between different candidates and explores possible detection channels for further $c\bar{c}-c\bar{c}$ states.

   hep-phhep-exPRD(2023)·25 citations
9. 09*

   Imprint of inflationary gravitational waves and WIMP dark matter in pulsar timing array data

   Debasish Borah🇮🇳 · Suruj Jyoti Das🇮🇳 · Rome Samanta🇨🇿

   Motivated by the recent release of new results from five different pulsar timing array (PTA) experiments claiming to have found compelling evidence for primordial gravitational waves (GW) at nano-Hz frequencies, we consider the prospects of generating such a signal from inflationary blue-tilted tensor power spectrum in a specific dark matter (DM) scenario dubbed as $\text{Miracle-less WIMP}$. While $\text{Miracle-less WIMP}$, due to insufficient interaction rate with the Standard Model (SM) bath gets thermally overproduced, inflationary blue-tilted gravitational waves (BGW) in compliance with PTA data, conflict cosmological observations if reheat temperature after inflation is sufficiently high. Both these issues are circumvented with late entropy dilution, bringing DM abundance within observational limits and creating a doubly-peaked feature in the BGW spectrum consistent with cosmological observations. The blue-tilted tail of the low-frequency peak can fit NANOGrav 15 yr data, while other parts of the spectrum are within reach of present and future GW experiments.

   hep-phastro-ph.COJCAP(2024)·40 citations
10. 10*

    Hidden-charm pentaquark states in a mass splitting model

    Shi-Yuan Li🇨🇳 · Yan-Rui Liu🇨🇳 · Zi-Long Man🇨🇳 · Zong-Guo Si🇨🇳 · Jing Wu🇨🇳

    Assuming that the $P_c(4312{)}^{+}$ is a $I(J^P)=\frac{1}{2}({\frac{3}{2}}^{-})$ compact pentaquark, we study the mass spectrum of its S-wave hidden-charm partner states in a color-magnetic interaction model. Combining the information from their decays obtained in a simple rearrangement scheme, one finds that the quantum numbers of $P_c(4457{)}^{+}$, $P_c(4440{)}^{+}$, and $P_c(4337{)}^{+}$ can be assigned to be $I(J^P)=\frac{1}{2}({\frac{3}{2}}^{-})$, $\frac{1}{2}({\frac{1}{2}}^{-})$, and $\frac{1}{2}({\frac{1}{2}}^{-})$, respectively, while both $P_{cs}(4338{)}^0$ and $P_{cs}(4459{)}^0$ can be interpreted as $I(J^P)=0({\frac{1}{2}}^{-})$ $udsc\bar{c}$ compact states. Based on the numerical results, we also find narrow pentaquarks in $ssnc\bar{c}$ ($n=u,d$) and $sssc\bar{c}$ systems. The decay properties of the studied pentaquarks and the searching channels for them can be tested in future experiments.

    hep-phhep-exhep-latnucl-thPRD(2023)·24 citations
11. 11*

    Analysis of the light $J^P=3^{-}$ mesons in QCD sum rules

    T.M.Aliev🇹🇷 · S.Bilmis🇹🇷 · M.Savci🇹🇷

    In this study, we investigate the masses and decay constants of the light mesons with $J^P=3^{-}$ ( ${\rho }_3,{\omega }_3,K_3,{\varphi }_3$) within the QCD sum rules method by taking into account $SU(3)$ violation effects. We state that our predictions on masses of the considered mesons are in good agreement with experimental data within the precision of the model.

    hep-phhep-exhep-latPRD(2023)·4 citations
12. 12*

    Polarization of recoil photon in non-linear Compton process

    A.I. Titov🇷🇺

    The polarization of recoil photon (${\gamma }^{\prime }$) in the non-linear Compton process $e+\vec{L}\to {\vec{\gamma }}^{\prime }+e^{\prime }$ in the interaction of a relativistic electron with a linearly polarized laser beam ($\vec{L}$) is studied within the Furry picture in the lowest-order, tree-level S matrix element. In particular, we consider the asymmetry of differential cross sections $\mathcal{A}$ for two independent axes describing the Compton process equal to the intrinsic spin variable ${\xi }_3^f$, that determines the polarization properties of ${\gamma }^{\prime }$. The sign and absolute value of the asymmetry determine the direction and degree of ${\gamma }^{\prime }$ polarization. We have analyzed the process in a wide range of laser intensity that covers existing and future experiments. Our results provide additional knowledge for studying nonlinear multi-photon effects in quantum electrodynamics and can be used in planning experiments at envisaged laser facilities.

    hep-phEur.Phys.J.D(2024)·1 citation
13. 13*

    A Novel Probe of Supersymmetry in Light of Nanohertz Gravitational Waves

    Kai Murai🇯🇵 · Wen Yin🇯🇵

    A new era of exploring the early Universe may have begun with the recent strong evidence for the stochastic gravitational wave (GW) background from the data reported by NANOGrav, EPTA, PPTA, and CPTA. Inspired by this, we propose a new potential source of stochastic GWs in the minimal supersymmetric standard model (MSSM), which could be the theory at a very high energy scale. This source is the "axion" field in the Higgs multiplets when the Higgs field takes a large value along the D-flat direction in the early Universe, for example, during inflation. The axion motion triggers the instability of the standard model $\mathrm{U}(1)$ and/or $\mathrm{SU}(3)$ gauge fields, producing stochastic GWs during the inflation. This scenario can be seen as a simple UV completion of the commonly studied models where an axion spectator/inflaton is coupled to a hidden $\mathrm{U}(1)$ or $\mathrm{SU}(N)$ gauge field without matter fields. Thus the nanohertz GWs may be a sign of supersymmetry. Primordial magnetic field production is also argued. In addition, we point out the simple possibility that this axion within the MSSM drives inflation.

    hep-phastro-ph.COJHEP(2023)·40 citations
14. 14*

    Fingerprint of GeV scale right-handed neutrinos on inflationary gravitational waves and PTA data

    Satyabrata Datta🇮🇳 · Rome Samanta🇨🇿

    We show that the seesaw mechanisms that exhibit right-handed neutrino mass-dependent non-standard post-inflationary cosmology make blue-tilted inflationary gravitational waves (GW) compatible with the recent findings of nHz stochastic GW background by the pulsar-timing arrays (PTAs) for high reheating temperatures. The right-handed neutrino (RHN) mass scale has to be $\mathcal{O}(\mathrm{GeV})$. Remarkably, such a scenario produces a correlated signature testable by the future LIGO run. In addition to contributing to the active neutrino masses, $\mathcal{O}(\mathrm{GeV})$ RHNs generate baryon asymmetry of the universe via low-scale-leptogenesis. They can be searched for in collider experiments. Therefore, the recent detection by PTAs is not only exciting for GWs in the nHz range; it paves the way to test and constrain well-studied mechanisms, such as seesaws, with a low-frequency and a correlated measurement of high-frequency GW spectral features, complementary to particle physics searches.

    hep-phastro-ph.COPRD(2023)·68 citations
15. 15*

    Scale of Dirac leptogenesis and left-right symmetry in the light of recent PTA results

    Basabendu Barman🇵🇱 · Debasish Borah🇮🇳 · Suruj Jyoti Das🇮🇳 · Indrajit Saha🇮🇳

    Motivated by the recent release of new results from five different pulsar timing array (PTA) experiments claiming to have found compelling evidence for primordial gravitational waves (GW) at nano-Hz frequencies, we study the consequences for two popular beyond the Standard Model (SM) frameworks, where such nano-Hz GW can arise due to annihilating domain walls (DW). Minimal framework of Dirac leptogenesis, as well as left-right symmetric model (LRSM) can lead to formation of DW due to spontaneous breaking of $Z_2$ symmetry. Considering the NANOGrav 15 yr data, we show that the scale of Dirac leptogenesis should be above $10^7$ GeV for conservative choices of Dirac Yukawa couplings with fine-tuning at the level of the SM. The scale of {\it minimal} LRSM is found to be more constrained $M_{\mathrm{LR}}\sim 10^6$ GeV in order to fit the NANOGrav 15 yr data. On the other hand, the {\it non-minimal} LRSM can be compatible with the NANOGrav data for $10^2\mathrm{TeV}\lesssim M_{\mathrm{LR}}\lesssim 10^3$ TeV but with the corresponding $B-L$ breaking scale violating collider bounds.

    hep-phastro-ph.COJCAP(2023)·48 citations
16. 16*

    Neutral current neutrino and antineutrino scattering off the polarized nucleon

    Krzysztof M. Graczyk🇵🇱 · Beata E. Kowal🇵🇱

    The elastic and inelastic neutral current $\nu$ ($\overline{\nu }$) scattering off the polarized nucleon is discussed. The inelastic scattering concerns the single-pion production process. We show that the spin asymmetries' measurement can help to distinguish between neutrino and antineutrino neutral current scattering processes. The spin asymmetries also encode information about a type of target. Eventually, detailed studies of the inelastic spin asymmetries can improve understanding of the resonant-nonresonant pion production mechanism.

    hep-phhep-exnucl-exnucl-thPRD(2023)·4 citations
17. 17*

    A new approach to QCD final-state evolution in processes with massive partons

    Benoit Assi🇺🇸 · Stefan Höche🇺🇸

    We present an algorithm for massive parton evolution which is based on the differentially accurate simulation of soft-gluon radiation by means of a non-trivial azimuthal angle dependence of the splitting functions. The kinematics mapping is chosen such as to to reflect the symmetry of the final state in soft-gluon radiation and collinear splitting processes. We compute the counterterms needed for a fully differential NLO matching and discuss the analytic structure of the parton shower in the NLL limit. We implement the new algorithm in the numerical code Alaric and present a first comparison to experimental data.

    hep-phPRD(2024)·47 citations
18. 18*

    Role of strange quarks in the $D$-term and cosmological constant term of the proton

    Ho-Yeon Won🇰🇷 · Hyun-Chul Kim🇰🇷 · June-Young Kim🇺🇸

    We investigate the mechanics of the proton by examining the flavor-decomposed proton cosmological constants and generalized vector form factors. The interplay of up, down, and strange quarks within the proton is explored, shedding light on its internal structure. The contributions of strange quarks play a crucial role in the $D$-term and cosmological constants. We find that the flavor blindness of the isovector $D$-term form factor is only valid in flavor SU(3) symmetry.

    hep-phhep-exhep-latPRD(2023)·18 citations
19. 19*

    Contribution of Coulomb interaction to elastic pp and p p\bar scattering in holographic QCD

    Yu-Peng Zhang🇨🇳 · Xun Chen🇨🇳 · Xiao-Hua Li🇨🇳 · Akira Watanabe🇨🇳

    The differential cross sections of elastic proton-proton (pp) and proton-antiproton (pp\bar) scattering are studied in a holographic QCD model, considering the strong and Coulomb interaction in the Regge regime. Based on previous studies of strong interactions described in terms of Pomeron and Reggeon exchange, we add the contribution of Coulomb interaction described by photon exchange. We present the momentum transfer dependence of the contribution rates for each component, especially for the Coulomb-nuclear interference, which refers to the cross term between both interactions. For the adjustable parameters for the strong interaction, we can adopt the values determined in previous studies, and there are no extra adjustable parameters that need to be determined for the Coulomb interaction. It is presented that the resulting differential cross sections are consistent with the data for pp and pp\bar scattering.

    hep-phPRD(2023)·5 citations
20. 20*

    Clockwork axion footprint on nano-hertz stochastic gravitational wave background

    Bo-Qiang Lu🇨🇳 · Cheng-Wei Chiang🇹🇼 · Tianjun Li🇨🇳

    The recent Pulsar Timing Arrays (PTAs) nano-Hz gravitational wave (GW) background signal can be naturally induced by the annihilation of domain walls (DWs) formed at a symmetry-breaking scale $f\simeq 200$~TeV in the clockwork axion framework. Based on our first successful and precise prediction, we for the first time suggest that the recent PTA observations strongly support the novel mechanism of the QCD instanton-induced DW annihilation in the clockwork axion framework. We also for the first time discover a novel correlation between dark matter (DM) relic abundance and nano-Hz GW background, which in turn indicates a natural connection between the axion decay constant and the symmetry-breaking scale in the clockwork framework. We find that the GW signal has a peak $h^2{\Omega }_{\mathrm{GW}}\simeq 10^{-6.6}-10^{-6.1}$ at about 50~nHz, which is definite and testable for future PTA data at frequencies $\gtrsim 25$~nHz and CMB-S4 experiment. We also propose various phenomena that may appear in PTAs and future GW interferometers.

    hep-phastro-ph.HEPRD(2024)·47 citations
21. 21*

    The hidden strange $B_c$-like molecular states

    Zhong-Yu Wang🇨🇳 · Zhi-Feng Sun🇨🇳

    With the chiral unitary approach, we evaluate the hidden strange $B_c$-like molecular states of $b\bar{c}s\bar{s}$ systems ${\bar{B}}_s{\bar{D}}_s$, ${\bar{B}}_s^{\ast }{\bar{D}}_s$, ${\bar{B}}_s{\bar{D}}_s^{\ast }$, and ${\bar{B}}_s^{\ast }{\bar{D}}_s^{\ast }$ coupled to the non-strange channels. The $S$-wave scattering amplitudes are calculated based on the vector meson exchange, four pseudoscalar mesons contact interactions, and four vector mesons contact interactions obtained from the extended local hidden gauge approach. We find six states below the threshold of the most relevant channel. The binding energies of these states are around $1-10$ MeV and the widths are around $0.2-0.7$ MeV. Our research is a supplement to the mass spectra of $B_c$-like states, which may be useful for the experimental search in the future.

    hep-phEPJC(2023)·4 citations
22. 22*

    New Method for Measuring the Ratio ${\mu }_p{G}_E/G_M$ Based on the Polarization Transfer from the Initial Proton to the Final Electron in the $e\vec{p}\to \vec{e}p$ Process

    M.V. Galynskii🇧🇾 · Yu.M. Bystritskiy🇷🇺 · V.M. Galynsky

    In this letter, we propose a new method for measuring the Sachs form factors ratio ($R={\mu }_p{G}_E/G_M$) based on the transfer of polarization from the initial proton to the final electron in the elastic $e\vec{p}\to \vec{e}p$ process, in the case when the axes of quantization of spins of the target proton at rest and of the scattered electron are parallel, i.e., when an electron is scattered in the direction of the spin quantization axis of the proton target. To do this, in the kinematics of the SANE collaboration experiment (2020) on measuring double spin asymmetry in the $\vec{e}\vec{p}\to ep$ process, using Kelly (2004) and Qattan (2015) parametrizations, a numerical analysis was carried out of the dependence of the longitudinal polarization degree of the scattered electron on the square of the momentum transferred to the proton, as well as on the scattering angles of the electron and proton. It is established that the difference in the longitudinal polarization degree of the final electron in the case of conservation and violation of scaling of the Sachs form factors can reach 70%. This fact can be used to set up polarization experiments of a new type to measure the ratio $R$.

    hep-phhep-exPRD(2023)·1 citation
23. 23*

    Innovative Polarimetry for High$-$energy Cosmic $\gamma$ and $e^{+}/e^{-}$ Induced by Vector Photo$-$productionn

    Dart-yin A. Soh🇹🇼 · Zhaoyi Qu🇨🇳

    In this paper, we explore the possibility of measuring the complete polarizations of cosmic photons $\gamma$ and the polarizations of cosmic electrons $e^{-}$ and positrons $e^{+}$. Our innovative Vector Meson Photo-production induced polarimetry enables people to measure the circular plarization compoent of a $GeV$ $\gamma$ and to improve its linear polarization measurement, and thus enables people to measure the polarization of $GeV$ $e^{+}/e^{-}$ for the first time. We calculate the production process of ${\pi }^{+}{\pi }^{-}$ by a generally polarized photon near nucleon's field in a generalized VPD-SDMEs Factorization with the fitted experimental data, so that it's partially model-independent. We also propose the observables and approach to measure their polarizations based on our calculations. Our new polarimetry of high-energy cosmic $\gamma ,e^{+},e^{-}$ will open a new window to reveal the mysteries and solve the puzzles of BSM new physics in particle physics and cosmology.

    hep-phastro-ph.HE1 citation
24. 24*

    Implications of Nano-Hertz Gravitational Waves on Electroweak Phase Transition in the Singlet Dark Matter Model

    Yang Xiao🇨🇳 · Jin Min Yang🇨🇳 · Yang Zhang🇨🇳

    Inspired by the recent evidences of nano-Hertz stochastic gravitational waves observed by the pulsar timing array collaborations, we explore their implied supercooled electroweak phase transition in the singlet extension of the Standard Model. Our findings reveal that by adjusting the model parameter at per milli level, the corresponding percolation temperature can be continuously lowered to 1 GeV. With such a low percolation temperature, the singlet dark matter may freeze out before the electroweak phase transition, and, consequently, the entropy generated during the transition can significantly affect the dark matter relic density. It alleviates the tension between the requirement of a strong electroweak phase transition and the constraints imposed by dark matter direct detection, and can be tested in future experiments.

    hep-phSci.Bull.(2023)·62 citations
25. 25*

    A collider test of nano-Hertz gravitational waves from pulsar timing arrays

    Shao-Ping Li🇨🇳 · Ke-Pan Xie🇨🇳

    A cosmic first-order phase transition (FOPT) occurring at MeV-scale provides an attractive explanation for the nano-Hertz gravitational wave (GW) background indicated by the recent pulsar timing array data from the NANOGrav, CPTA, EPTA and PPTA collaborations. We propose this explanation can be further tested at the colliders if the hidden sector couples to the Standard Model sector via Higgs portal. Through a careful analysis of the thermal history of the hidden sector, we demonstrate that in order to successfully explain the observed GW signal, the portal coupling must be sizable that it can be probed through Higgs invisible decay at the LHC or future lepton colliders such as CEPC, ILC, and FCC-ee. Our research offers a promising avenue to uncover the physical origin of the nano-Hertz GWs through particle physics experiments.

    hep-phastro-ph.COPRD(2023)·79 citations
26. 26*

    Fuzzy Dark Matter and the Dark Dimension

    Luis A. Anchordoqui🇺🇸 · Ignatios Antoniadis🇫🇷 · Dieter Lust🇩🇪

    We propose a new dark matter contender within the context of the so-called ``dark dimension'', an innovative 5-dimensional construct that has a compact space with characteristic length-scale in the micron range. The new dark matter candidate is the radion, a bulk scalar field whose quintessence-like potential drives an inflationary phase described by a 5-dimensional de Sitter (or approximate) solution of Einstein equations. We show that the radion could be ultralight and thereby serve as a fuzzy dark matter candidate. We advocate a simple cosmological production mechanism bringing into play unstable Kaluza-Klein graviton towers which are fueled by the decay of the inflaton.

    hep-phhep-thEPJC(2024)·47 citations
27. 27*

    Pinning down the leptophobic $Z^{\prime }$ in leptonic final states with Deep Learning

    Tanumoy Mandal🇮🇳 · Aniket Masaye🇮🇳 · Subhadip Mitra🇮🇳 · Cyrin Neeraj🇮🇳 · Naveen Reule🇮🇳 · Kalp Shah🇮🇳

    A leptophobic $Z^{\prime }$ that does not couple with the Standard Model leptons can evade the stringent bounds from the dilepton-resonance searches. In our earlier paper [T. Arun et al., Search for the $Z^{\prime }$ boson decaying to a right-handed neutrino pair in leptophobic $U(1)$ models, Phys. Rev. D, 106 (2022) 095035; arXiv:2204.02949], we presented two gauge anomaly-free $U(1)$ models -- one based on the Green-Schwarz (GS) anomaly cancellation mechanism, and the other on a grand unified theory (GUT) framework with gauge kinetic mixing -- where a heavy leptophobic $Z^{\prime }$ is present along with right-handed neutrinos ($N_R$). We pointed out the interesting possibility of a correlated search for $Z^{\prime }$ and $N_R$ at the LHC through the $pp\to Z^{\prime }\to N_R{N}_R$ channel. This channel can probe a part of the $Z^{\prime }$ parameter space beyond the reach of the standard dijet resonance searches. In this follow-up paper, we analyse the challenging monolepton final state arising from the decays of the $N_R$ pair with Deep Learning. We present the high-luminosity LHC discovery reaches for six different GUT embeddings and a benchmark point in the GS setup. We also update our previous estimates in the dilepton channel with Deep Learning. We identify parameter regions that can be probed with the proposed channel but will remain inaccessible to dijet searches at the HL-LHC.

    hep-phhep-exhep-thPLB(2024)·3 citations
28. 28*

    The Standard Model theory of neutron beta decay

    Mikhail Gorchtein🇩🇪 · Chien-Yeah Seng🇺🇸

    We review the status of the Standard Model theory of neutron beta decay. Particular emphasis is put on the recent developments in the electroweak radiative corrections. Given that some existing approaches give slightly different results, we thoroughly review the origin of discrepancies, and provide our recommended value for the radiative correction to the neutron and nuclear decay rates. The use of dispersion relation, lattice Quantum Chromodynamics and effective field theory framework allows for high-precision theory calculations at the level of $10^{-4}$, turning neutron beta decay into a powerful tool to search for new physics, complementary to high-energy collider experiments. We offer an outlook to the future improvements.

    hep-phnucl-exnucl-thUniverse(2023)·26 citations
29. 29*

    Extraction of the strong coupling with HERA and EIC inclusive data

    Salim Cerci🇹🇷 · Zuhal Seyma Demiroglu🇺🇸 · Abhay Deshpande🇺🇸 · Paul R. Newman🇬🇧 · Barak Schmookler🇺🇸 · Deniz Sunar Cerci🇹🇷 · Katarzyna Wichmann🇩🇪

    Sensitivity to the strong coupling ${\alpha }_S(M_Z^2)$ is investigated using existing Deep Inelastic Scattering data from HERA in combination with projected future measurements from the Electron Ion Collider (EIC) in a next-to-next-to-leading order QCD analysis. A potentially world-leading level of precision is achievable when combining simulated inclusive neutral current EIC data with inclusive charged and neutral current measurements from HERA, with or without the addition of HERA inclusive jet and dijet data. The result can be obtained with substantially less than one year of projected EIC data at the lower end of the EIC centre-of-mass energy range. Some questions remain over the magnitude of uncertainties due to missing higher orders in the theoretical framework.

    hep-phhep-exhep-thnucl-ex+1EPJC(2023)·17 citations
30. 30*

    HNL see-saw: lower mixing limit and pseudodegenerate state

    Igor Krasnov🇷🇺

    Heavy Neutral Leptons are popular hypothetical particles, first introduced as a way to explain neutrino oscillations, and since then extensively studied in relation to many other aspects of physics beyond the Standard Model. They also serve as viable targets for direct experimental searches, being effectively described only by HNL mass and mixing with each neutrino flavor. Motivated by this, we study the lower theoretical boundary for mixing with a specified flavor in two and three HNLs cases. We find the connection of this limit with the effective neutrino mass appearing in neutrinoless double beta decay (and similar expressions for mixing with muon and tau neutrino). In two HNLs case, there is a rather strict relation between mixing of different HNLs with the same neutrino flavor. We find that existing exclusion regions and their expected expansions in the near future are all described by a certain limit. We call that limit pseudodegenerate and find its relation to the symmetrical limit, already studied in the literature. We also study pseudodegenerate limit and conditions under which it is achieved in three HNLs case.

    hep-ph4 citations
31. 31*

    NANOGrav signal from axion inflation

    Xuce Niu🇺🇸 · Moinul Hossain Rahat🇬🇧

    Several pulsar timing arrays including NANOGrav, EPTA, PPTA, and CPTA have recently reported the observation of a stochastic background of gravitational wave spectrum in the nano-Hz frequencies. An inflationary interpretation of this observation is challenging from various aspects. We report that such a signal can arise from the Chern-Simons coupling in axion inflation, where a pseudoscalar inflaton couples to a (massive) $U(1)$ gauge field, leading to efficient production of a transverse gauge mode. Such tachyonic particle production during inflation exponentially enhances the primordial perturbations and leads to a unique parity-violating gravitational wave spectrum, that remains flat near the CMB scales but becomes blue-tilted at smaller scales. We identify the parameter space consistent with various cosmological constraints and show that the resultant gravitational wave signals can provide extra contribution on top of the standard astrophysical contribution from inspiraling supermassive black hole binaries towards explaining the observed excess at NANOGrav. The parity-violating nature of the signal can be probed in future interferometers, distinguishing it from most other new physics signals attempting to explain the NANOGrav result.

    hep-phastro-ph.HEhep-thPRD(2023)·79 citations
32. 32*

    Resonant screening in dense and magnetized QCD matter

    Guojun Huang🇨🇳 · Jiaxing Zhao🇫🇷 · Pengfei Zhuang🇨🇳

    We calculate the Debye screening mass in thermal, dense and magnetized QCD matter in the frame of resummed perturbation theory. In the limit of zero temperature, when the Landau energy level and Fermi surface of quarks match each other ${\mu }_q^2=2n|qB|$, where $q$, ${\mu }_q$ and $B$ are respectively the quark electric charge, chemical potential and external magnetic field, the screening mass diverges and the system is in the state of weakly interacting parton gas, which is very different from the known result of strongly interacting quark-gluon plasma at high temperature. The divergence disappears in thermal medium, but the screening mass oscillates with clear peaks at the matched magnetic field.

    hep-phnucl-thPRD(2023)·3 citations
33. 33*

    Boundaries and Interfaces with Localized Cubic Interactions in the $O(N)$ Model

    Sabine Harribey🇸🇪 · Igor R. Klebanov🇺🇸 · Zimo Sun🇺🇸

    We explore a new approach to boundaries and interfaces in the $O(N)$ model where we add certain localized cubic interactions. These operators are nearly marginal when the bulk dimension is $4-ϵ$, and they explicitly break the $O(N)$ symmetry of the bulk theory down to $O(N-1)$. We show that the one-loop beta functions of the cubic couplings are affected by the quartic bulk interactions. For the interfaces, we find real fixed points up to the critical value $N_{\mathrm{crit}}\approx 7$, while for $N>4$ there are IR stable fixed points with purely imaginary values of the cubic couplings. For the boundaries, there are real fixed points for all $N$, but we don't find any purely imaginary fixed points. We also consider the theories of $M$ pairs of symplectic fermions and one real scalar, which have quartic $OSp(1|2M)$ invariant interactions in the bulk. We then add the $Sp(2M)$ invariant localized cubic interactions. The beta functions for these theories are related to those in the $O(N)$ model via the replacement of $N$ by $1-2M$. In the special case $M=1$, there are boundary or interface fixed points that preserve the $OSp(1|2)$ symmetry, as well as other fixed points that break it.

    ↳ hep-thcond-mat.stat-mechhep-phJHEP(2023)·21 citations
34. 34*

    Search for environment-dependent dilatons

    Hauke Fischer🇦🇹 · Christian Käding🇦🇹 · René I.P. Sedmik🇦🇹 · Hartmut Abele🇦🇹 · Philippe Brax🇫🇷 · Mario Pitschmann🇦🇹

    The environment-dependent dilaton field is a well-motivated candidate for dark energy and naturally arises in the strong coupling limit of string theory. In this article, we present the very first experimental constraints on the parameters of this model. For this, we employ data obtained from the qBounce collaboration and the Lunar Laser Ranging (LLR) experiment. Furthermore, we forecast expected exclusion plots for the Casimir And Non Newtonian force EXperiment (Cannex) soon to be realised in an improved setup. Finally, we provide a detailed analysis of the screening mechanism and additional symmetries of the dilaton field theory.

    ↳ gr-qcastro-ph.COhep-phnucl-exPhys.Dark Univ.(2024)·19 citations
35. 35*

    Decaying Dark Matter and the Hubble Tension

    Andreas Nygaard🇩🇰 · Emil Brinch Holm🇩🇰 · Thomas Tram🇩🇰 · Steen Hannestad🇩🇰

    Decaying dark matter models generically modify the equation of state around the time of dark matter decay, and this in turn modifies the expansion rate of the Universe through the Friedmann equation. Thus, a priori, these models could solve or alleviate the Hubble tension, and depending on the lifetime of the dark matter, they can be classified as belonging to either the early- or late-time solutions. Moreover, decaying dark matter models can often be realized in particle physics models relatively easily. However, the implementations of these models in Einstein--Boltzmann solver codes are non-trivial, so not all incarnations have been tested. It is well known that models with very late decay of dark matter do not alleviate the Hubble tension, and in fact, cosmological data puts severe constraints on the lifetime of such dark matter scenarios. However, models in which a fraction of the dark matter decays to dark radiation at early times hold the possibility of modifying the effective equation of state around matter-radiation equality without affecting late-time cosmology. This scenario is therefore a simple realization of a possible early-time solution to the Hubble tension, and cosmological parameter estimation with current data in these models yields a value of $H_0=68.73_{-1.3}^{+0.81}$ at $68\%$ C.I.. This still leads to a $2.7\sigma$ Gaussian tension with the representative local value of $H_0=73.2\pm 1.3$ km s${}^{-1}$ Mpc${}^{-1}$. Additional work is, however, required to test more complex decay scenarios, which could potentially prefer higher values of $H_0$ and provide a better solution to the Hubble tension.

    ↳ astro-ph.COhep-ph10 citations
36. 36*

    Harvesting energy driven by Comisso-Asenjo process from Kerr-MOG black holes

    Mohsen Khodadi🇮🇷 · David F. Mota🇳🇴 · Ahmad Sheykhi🇮🇷

    Magnetic reconnection is a process that plays a critical role in plasma astrophysics by converting magnetic energy into plasma particle energy. Recently, Comisso and Asenjo demonstrated that rapid magnetic reconnection within a black hole's ergosphere can efficiently extract energy from a rotating black hole. In this paper, by considering a Kerr black hole in the MOdified gravity (MOG) framework, we investigate the impact of the MOG parameter $\alpha$ on the rotational energy extraction via the Comisso-Asenjo process (CAP). To model energy extraction from supermassive black holes located in the center of galaxies, we set the value of $\alpha$ within the range inferred from the recent observation of Sgr A* by the Event Horizon Telescope (EHT). Our results indicate that the Kerr-MOG black hole is a more efficient host for CAP-based rotational energy extraction compared to the Kerr black hole, since it amplifies the power of energy extraction and efficiency of the plasma energization process. We show that, from the energy extraction viewpoint, the CAP is more efficient than the Blandford-Znajek process (BZP). The latter is another magnetic field-based energy extraction model which is widely believed to be an engine for powering the high-energy astrophysics jets emerging from the supermassive black holes at active galactic nuclei. In particular, we show that the ratio of the energy extraction power of CAP to BZP in the presence of the MOG parameter is greater than that of the Kerr black hole. Our results promise this phenomenological message that the MOG-induced correction on the Kerr black hole background plays an important role in favor of energy extraction via the CAP.

    ↳ astro-ph.HEgr-qchep-phhep-thJCAP(2023)·29 citations
37. 37*

    Imprints of dark matter-massive neutrino interaction in upcoming post-reionization and galaxy surveys

    Antara Dey🇮🇳 · Arnab Paul🇮🇳 · Supratik Pal🇮🇳

    We explore possible signatures of the interaction between dark matter (DM) and massive neutrinos during the post-reionization epoch. Using both Fisher matrix forecast analysis and Markov Chain Monte-Carlo (MCMC) simulation, we conduct a thorough investigation of the constraints and imprints of the scenario on the upcoming post-reionization and galaxy surveys. Our investigation focuses on two key parameters: the strength of the DM-massive neutrino interaction ($u$) and the total neutrino mass ($M_{\mathrm{tot}}$), on top of the usual 6 cosmological parameters. We utilize future 21-cm intensity mapping, galaxy clustering as well as cosmic shear observations in order to investigate the possible constraints of these parameters in the future observations: Square Kilometre Array (SKA1 and SKA2) and Euclid, taking both conservative and realistic approaches. All these missions show promise in constraining both the parameters $u$ and $M_{\mathrm{tot}}$ by few orders compared to the current constraints from Planck18 (SKA2 performing the best among them). Although we do not find much improvement in $H_0$ and ${\sigma }_8$ tensions from our forecast analysis, SKA2 constrains them better in conservative approach. We further perform a brief investigation of the prospects of some of the next generation Cosmic Microwave Background (CMB) missions in combinations with LSS experiments in improving the constraints. Our analysis reveals that both SKA2 and CMB-S4 + Euclid + SKA1 IM2 combination will put the strongest bounds on the model parameters.

    ↳ astro-ph.COhep-phMNRAS(2023)·5 citations
38. 38*

    The Multi-mode Acoustic Gravitational Wave Experiment: MAGE

    William M. Campbell🇦🇺 · Maxim Goryachev🇦🇺 · Michael E. Tobar🇦🇺

    The Multi-mode Acoustic Gravitational wave Experiment (MAGE) is a high frequency gravitational wave detection experiment. In its first stage, the experiment features two near-identical quartz bulk acoustic wave resonators that act as strain antennas with spectral sensitivity as low as $6.6\times 10^{-21}\left[\text{strain}\right]/\sqrt{\text{Hz}}$ in multiple narrow bands across MHz frequencies. MAGE is the successor to the initial path-finding experiments; GEN 1 and GEN 2. These precursor runs demonstrated the successful use of the technology, employing a single quartz gravitational wave detector that found significantly strong and rare transient features. As the next step to this initial experiment, MAGE will employ further systematic rejection strategies by adding an additional quartz detector such that localised strains incident on just a single detector can be identified. The primary goals of MAGE will be to target signatures arising from objects and/or particles beyond that of the standard model, as well as identifying the source of the rare events seen in the predecessor experiment. The experimental set-up, current status and future directions for MAGE are discussed. Calibration procedures of the detector and signal amplification chain are presented. The sensitivity of MAGE to gravitational waves is estimated from knowledge of the quartz resonators. Finally, MAGE is assembled and tested in order to determine the thermal state of its new components.

    ↳ gr-qcastro-ph.HEastro-ph.IMhep-phSci.Rep.(2024)·23 citations
39. 39*

    Implications for the Supermassive Black Hole Binaries from the NANOGrav 15-year Data Set

    Yan-Chen Bi🇨🇳 · Yu-Mei Wu🇨🇳 · Zu-Cheng Chen🇨🇳 · Qing-Guo Huang🇨🇳

    NANOGrav, EPTA, PPTA, and CPTA have announced the evidence for a stochastic signal from their latest data sets. Supermassive black hole binaries (SMBHBs) are supposed to be the most promising gravitational-wave (GW) sources of pulsar timing arrays. Assuming an astro-informed formation model, we use the NANOGrav 15-year data set to constrain the gravitational wave background (GWB) from SMBHBs. Our results prefer a large turn-over eccentricity of the SMBHB orbit when GWs begin to dominate the SMBHBs evolution. Furthermore, the GWB spectrum is extrapolated to the space-borne GW detector frequency band by including inspiral-merge-cutoff phases of SMBHBs and should be detected by LISA, Taiji and TianQin in the near future.

    ↳ astro-ph.COgr-qchep-phSCPMA(2023)·95 citations
40. 40*

    Analog Sommerfeld law in quantum vacuum

    G.E. Volovik🇫🇮

    The activation temperature $T$ in the de Sitter environment is twice larger than the Gibbons-Hawking temperature, related to the cosmological horizon. We consider the activation temperature as the local temperature of the de Sitter vacuum, and construct the local thermodynamics of the de Sitter state. This thermodynamics includes also the gravitational coupling $K$ and the scalar Riemann curvature $\mathcal{R}$ as the thermodynamically conjugate variables. These variables modify the thermodynamics of the Gibbs-Duhem relation in the de Sitter state. The free energy density is proportional to $-T^2$, which is similar to that in the non-relativistic Fermi liquids and in relativistic matter with equation of state $w=1$. The local entropy is proportional to the local temperature, while the total entropy inside the cosmological horizon is $A/4G$, where $A$ is the area of the horizon. This entropy is usually interpreted as the entropy of the cosmological horizon. We also consider the possible application of the de Sitter thermodynamics to the Schwarzschild-de Sitter black hole and to black and white holes with the de Sitter cores.

    ↳ gr-qccond-mat.otherhep-phJETP Lett.(2023)·9 citations
41. 41*

    Generation of narrow beams of ultrarelativistic positrons (electrons) in the resonant strong electromagnetic field-assisted Breit-Wheeler process

    S.P. Roshchupkin🇷🇺 · V.D. Serov🇷🇺 · V.V. Dubov🇷🇺

    The resonant external field-assisted Breit-Wheeler process (Oleinik resonances) for strong electromagnetic fields with intensities less than the critical Schwinger field has been theoretically studied. The resonant kinematics has been studied in detail. The case of high-energy initial gamma quanta and emerging ultrarelativistic electron-positron pairs is studied. The resonant differential cross section is obtained. The generation of narrow beams of ultrarelativistic positrons (for Channel A) and electrons (for Channel B) is predicted with a probability significantly exceeding corresponding to the non-resonant process.

    ↳ physics.plasm-phhep-phPhoton.(2023)·7 citations
42. 42*

    Dilaton chiral perturbation theory at next-to-leading order

    Andrew Freeman🇺🇸 · Maarten Golterman🇺🇸 · Yigal Shamir🇮🇱

    We apply dilaton chiral perturbation theory (dChPT) at next-to-leading order to lattice data from the LatKMI collaboration for the eight-flavor SU(3) gauge theory. In previous work, we found that leading-order dChPT does not account for these data, but that a model extension of leading-order dChPT with a varying mass anomalous dimension describes these data well. Here we calculate the next-to-leading order corrections for the pion mass and decay constant. We focus on these quantities, as data for the dilaton mass are of poorer quality. The application of next-to-leading order dChPT is difficult because of the large number of new low-energy constants, and the results of our fits turn out to be inconclusive. They suggest -- yet cannot firmly establish -- that the LatKMI mass range might be outside the scope of dChPT.

    ↳ hep-lathep-phPRD(2023)·11 citations
43. 43*

    Implications for the non-Gaussianity of curvature perturbation from pulsar timing arrays

    Lang Liu🇨🇳 · Zu-Cheng Chen🇨🇳 · Qing-Guo Huang🇨🇳

    The recently released data by pulsar timing array (PTA) collaborations present strong evidence for a stochastic signal consistent with a gravitational-wave background. Assuming this signal originates from scalar-induced gravitational waves, we jointly use the PTA data from the NANOGrav 15-yr data set, PPTA DR3, and EPTA DR2 to probe the small-scale non-Gaussianity. We put the first-ever constraint on the non-Gaussianity parameter, finding $|F_{\mathrm{NL}}|\lesssim 13.9$ for a lognormal power spectrum of the curvature perturbations. Furthermore, we obtain $-13.9\lesssim F_{\mathrm{NL}}\lesssim -0.1$ to prevent excessive production of primordial black holes. Moreover, the multi-band observations with the space-borne gravitational-wave detectors, such as LISA/Taiji/TianQin, will provide a complementary investigation of primordial non-Gaussianity. Our findings pave the way to constrain inflation models with PTA data.

    ↳ astro-ph.COgr-qchep-phPRD(2024)·182 citations
44. 44*

    Minimal Supergeometric Quantum Field Theories

    Viola Gattus🇬🇧 · Apostolos Pilaftsis🇬🇧

    We formulate minimal SuperGeometric Quantum Field Theories (SG-QFTs) that allow for scalar-fermion field transformations in a manifestly reparameterisation covariant manner. First, we discuss the issue of uniqueness in defining the field-space supermetric of the underlying supermanifold, and clarify the fact that different supermetric definitions can lead to distinct theories in the off-shell kinematic region. By adopting natural choices for the field-space supermetric, we~then show that scalar fields alone cannot induce a non-trivial field-space Riemannian curvature in the fermionic sector, beyond the one originating from the scalar part of the theory. We~present for the first time minimal SG-QFT models that feature non-zero fermionic curvature both in two and four spacetime dimensions. Physical applications of SG-QFTs are discussed.

    ↳ hep-thhep-phPLB(2023)·27 citations
45. 45*

    Bootstrapping Pions at Large $N$. Part II: Background Gauge Fields and the Chiral Anomaly

    Jan Albert🇺🇸 · Leonardo Rastelli🇺🇸

    We continue the program [1] of carving out the space of large $N$ confining gauge theories by modern S-matrix bootstrap methods, with the ultimate goal of cornering large $N$ QCD. In this paper, we focus on the effective field theory of massless pions coupled to background electromagnetic fields. We derive the full set of positivity constraints encoded in the system of 2 $\to$ 2 scattering amplitudes of pions and photons. This system probes a larger set of intermediate meson states, and is thus sensitive to intricate large $N$ selection rules, especially when supplemented with expectations from Regge theory. It also has access to the coefficient of the chiral anomaly. We find novel numerical bounds on several ratios of Wilson coefficients, in units of the rho mass. By matching the chiral anomaly with the microscopic theory, we also derive bounds that contain an explicit $N$ dependence.

    ↳ hep-thhep-phJHEP(2024)·64 citations
46. 46*

    Gravitational Waves from Stochastic Scalar Fluctuations

    Reza Ebadi🇺🇸 · Soubhik Kumar🇺🇸 · Amara McCune🇺🇸 · Hanwen Tai🇺🇸 · Lian-Tao Wang🇺🇸

    We present a novel mechanism for gravitational wave generation in the early Universe. Light spectator scalar fields during inflation can acquire a blue-tilted power spectrum due to stochastic effects. We show that this effect can lead to large curvature perturbations at small scales (induced by the spectator field fluctuations) while maintaining the observed, slightly red-tilted curvature perturbations at large cosmological scales (induced by the inflaton fluctuations). Along with other observational signatures, such as enhanced dark matter substructure, large curvature perturbations can induce a stochastic gravitational wave background (SGWB). The predicted strength of SGWB in our scenario, ${\Omega }_{\mathrm{GW}}{h}^2\simeq 10^{-20}-10^{-15}$, can be observed with future detectors, operating between $10^{-5}$ Hz and 10 Hz. We note that, in order to accommodate the newly reported NANOGrav observation, one could consider the same class of spectator models. At the same time, one would need to go beyond the simple benchmark considered here and consider a regime in which a misalignment contribution is also important.

    ↳ astro-ph.COgr-qchep-phPRD(2024)·49 citations
47. 47*

    Did we hear the sound of the Universe boiling? Analysis using the full fluid velocity profiles and NANOGrav 15-year data

    Tathagata Ghosh🇮🇳 · Anish Ghoshal🇵🇱 · Huai-Ke Guo🇨🇳 · Fazlollah Hajkarim🇺🇸 · Stephen F King🇬🇧 · Kuver Sinha🇺🇸 · Xin Wang🇬🇧 · Graham White🇬🇧

    In this paper, we analyse sound waves arising from a cosmic phase transition where the full velocity profile is taken into account as an explanation for the gravitational wave spectrum observed by multiple pulsar timing array groups. Unlike the broken power law used in the literature, in this scenario the power law after the peak depends on the macroscopic properties of the phase transition, allowing for a better fit with pulsar timing array (PTA) data. We compare the best fit with that obtained using the usual broken power law and, unsurprisingly, find a better fit with the gravitational wave (GW) spectrum that utilizes the full velocity profile. We then discuss models that can produce the best-fit point and complementary probes using CMB experiments and searches for light particles in DUNE, IceCUBE-Gen2, neutrinoless double beta decay, and forward physics facilities at the LHC like FASER nu, etc.

    ↳ astro-ph.HEhep-phJCAP(2024)·87 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.