Mon·Jul 12, 2021Monday·July 12, 2021

1. 01*

   Initial State Radiation in the Herwig 7 Angular-Ordered Parton Shower

   Gavin Bewick🇬🇧 · Silvia Ferrario Ravasio🇬🇧 · Peter Richardson🇬🇧 · Michael H. Seymour🇬🇧

   We study the simulation of initial-state radiation in angular-ordered parton showers in order to investigate how different interpretations of the ordering variable affect the logarithmic accuracy of such showers. This also enables us to implement a recoil scheme which is consistent between final-state and initial-state radiation. We present optimal values of the strong coupling and intrinsic transverse momentum to be used in each version of the parton shower, tuned using $Z^0$-boson production at the LHC at 7 TeV. With these tuned showers, we perform a phenomenological study of the Drell-Yan process at several centre-of-mass energies.

   hep-phJHEP(2022)·29 citations
2. 02*

   Indirect Searches for Secluded Dark Matter

   C. Siqueira🇧🇷 · Guilherme N. Fortes🇧🇷 · Aion Viana🇧🇷 · Farinaldo Queiroz🇧🇷

   Dark matter is one of the most important open problems in particle physics and cosmology. Weakly interacting massive particles (WIMPs) appear as an appealing solution, providing the right relic density with a cross-section at the electroweak scale, however, no WIMP signals were observed until now. Secluded models are good alternatives to the standard ones. In this case, instead of a direct annihilation to the standard model (SM) particles, the dark matter annihilates into mediators which subsequently decay into SM particles. In this way, secluded models may avoid the stringent limits from direct searches, and, at the same time, be probed by indirect detection experiments. Motivated by the appearance of secluded dark matter in several model building endeavors, in this talk, we will present the sensitivity of several gamma-ray instruments (current and prospects), including Fermi-LAT, H.E.S.S., CTA, and SWGO, to secluded dark matter annihilations in the inner galactic halo, and in the dwarf spheroidal galaxies, covering a wide range dark matter masses, from tens of GeV to hundreds of TeV.

   hep-phPoS(2021)·7 citations
3. 03*

   Electron and muon magnetic moments and implications for dark matter and model characterisation in non-universal $U(1{)}^{\prime }$ supersymmetric models

   Mariana Frank🇨🇦 · Yaşar Hiçyılmaz🇬🇧 · Subhadeep Mondal🇮🇳 · Özer Özdal🇨🇦 · Cem Salih Ün🇹🇷

   We attribute deviations of the muon and electron magnetic moments from the theoretical predictions to the presence of an additional $U(1{)}^{\prime }$ supersymmetric model. We interpret the discrepancies between the muon and electron anomalous magnetic moments to be due to the presence of non-universal $U(1{)}^{\prime }$ charges. In a minimally extended model, we show that requiring both deviations to be satisfied imposes constraints on the spectrum of the model, in particular on dark matter candidates and slepton masses and ordering. Choosing three benchmarks with distinct dark matter features, we study implications of the model at colliders, concentrating on variables that can distinguish our non-universal scenario from other $U(1{)}^{\prime }$ implementations.

   hep-phJHEP(2021)·32 citations
4. 04*

   Nonperturbative ${\varphi }^4$ potentials: Phase transitions and light horizons

   Yuan Shi🇺🇸

   It is commonly believed that a massive real scalar field $\varphi$ only mediates short-range interactions on the scale of its Compton wavelength via the Yukawa potential. However, in the nonperturbative regime of nonlinear self coupling, $\varphi$ can also mediate larger scale interactions. Moreover, the classical potential, namely, the static configuration of $\varphi$ in the presence of an external source, is not always unique for given boundary conditions. In this paper, a complete set of finite-energy potentials (FEPs) induced by a Gaussian source is identified in one, two, and three spatial dimensions when the nonlinearity is of the Mexican-hat type, which is often prescribed to induce spontaneous symmetry breaking. In the size-strength parameter space of the source, phase boundaries are mapped out, across which the number of FEPs differ. Additionally, softer phase transitions are delineated according to whether the potential exhibits a light horizon at which $\varphi$ vanishes. The light horizon is of physical significance when $\varphi$ couples with other particles. For example, when $\varphi$ is the Higgs field, all elementary particles become massless at the light horizon. It is remarkable that white dwarfs and neutron stars are potentially in a phase where light horizons exist, whose outer radii are a few times the star sizes. Moreover, suppose elementary fermions of mass greater than $\sim 10^3$ GeV exist, then they may also be surrounded by light horizons with radii comparable to the Higgs Compton wavelength. Finally, nonperturbative states may also be realized in condensed matter systems, wherein phase transitions are controllable using localized sources.

   hep-ph1 citation
5. 05*

   Searching for Dark Matter in the Sun using Hyper-Kamiokande

   Nicole F. Bell🇦🇺 · Matthew J. Dolan🇦🇺 · Sandra Robles🇦🇺

   We study the ability of the Hyper-Kamiokande (HyperK) experiment, currently under construction, to constrain a neutrino signal produced via the annihilation of dark matter captured in the Sun. We simulate upward stopping and upward through-going muon events at HyperK, using Super-Kamiokande (SuperK) atmospheric neutrino results for validation, together with fully and partially contained events. Considering the annihilation of dark matter to various standard model final states, we determined the HyperK sensitivity to the dark matter spin-dependent scattering cross-section. We find that HyperK will improve upon current SuperK limits by a factor of 2-3, with a further improvement in sensitivity possible if systematic errors can be decreased relative to SuperK.

   hep-phastro-ph.COastro-ph.SRhep-exJCAP(2021)·33 citations
6. 06*

   Gravitational Wave From Axion-like Particle Inflation

   Wei Cheng🇨🇳 · Tao Qian🇨🇳 · Qing Yu🇨🇳 · Hua Zhou🇨🇳 · Rui-Yu Zhou🇨🇳

   In this paper, we investigate the Axion-like Particle inflation by applying the multi-nature inflation model, where the end of inflation is achieved through the phase transition (PT). The events of PT should not be less than $200$, which results in the free parameter $n\ge 404$. Under the latest CMB restrictions, we found that the inflation energy is fixed at $10^{15}\mathrm{GeV}$. Then, we deeply discussed the corresponding stochastic background of the primordial gravitational wave (GW) during inflation. We study the two kinds of $n$ cases, i.e., $n=404,2000$. We observe that the magnitude of $n$ is negligible for the physical observations, such as $n_s$, $r$, $\Lambda$, and ${\Omega }_{\mathrm{GW}}{h}^2$. In the low-frequency regions, the GW is dominated by the quantum fluctuations, and this GW can be detected by Decigo at $10^{-1}\mathrm{Hz}$. However, GW generated by PT dominates the high-frequency regions, which is expected to be detected by future 3DSR detector.

   hep-phastro-ph.COastro-ph.HEPRD(2021)·12 citations
7. 07*

   Hadronic Currents and Form Factors in three-body Semileptonic $\tau$ Decays

   Fabian Krinner🇩🇪 · Stephan Paul🇩🇪

   Three-body semileptonic $\tau$-decays offer a path to understand the properties of light hadronic systems and CP symmetry violations through searches for electric dipole moments. In studies of electro-weak physics, the hadronic part of the final states has traditionally been described using the language of form factors. Spectroscopic information, resolved in terms of orbital angular momentum quantum-numbers, is best being derived from an explicit decomposition of the hadronic current in the orbital angular momentum basis. Motivated by the upcoming large data samples from B factories, we present the full description of the hadronic currents decomposed into quantum numbers of the hadronic final state using the isobar picture. We present formulas for orbital angular momenta up to three and apply the rules derived from hadron spectroscopy to formulate the decay chain of hadronic three-body systems of arbitrary mass. We also translate this formalism to the language of form factors and thereby correct insufficiencies found in previous analyses of three-body hadronic final states.

   hep-phEPJC(2021)·6 citations
8. 08*

   Holographic Colour Superconductors at Finite Coupling with NJL Interactions

   Kazem Bitaghsir Fadafan🇮🇷 · Jesús Cruz Rojas🇬🇧

   We study a bottom-up holographic description of the QCD colour superconducting phase in the presence of higher derivative corrections. We expand this holographic model in the context of Gauss-Bonnet (GB) gravity. The Cooper pair condensate has been investigated in the deconfinement phase for different values of the GB coupling parameter ${\lambda }_{GB}$, we observe a change in the value of the critical chemical potential ${\mu }_c$ in comparison to Einstein gravity. We find that ${\mu }_c$ grows as ${\lambda }_{GB}$ increases. We add four fermion interactions and show that in the presence of these corrections the main interesting features of the model are still present and that the intrinsic attractive interaction can not be switched off. This study suggests to find GB corrections to equation of state of holographic QCD matter.

   hep-phhep-thEPJC(2021)·6 citations
9. 09*

   Duality-symmetric axion electrodynamics and haloscopes of various geometries

   Dai-Nam Le🇻🇳 · Le Phuong Hoang🇻🇳 · Binh Xuan Cao🇻🇳

   Within the dual symmetric point of view, the theory for seeking axion dark matter via haloscope experiments is derived by exactly solving the dual symmetric axion electrodynamics equation. Notwithstanding that the conventional theory of axion electrodynamics presented in [Phys. Rev. Lett. 51, 1415 (1983) and J. Phys. A: Math. Gen. 19, L33 (1986)] is more commonly used in haloscope theory, we show that the dual symmetric axion electrodynamics has more advantages to apply to haloscope theory. First, the dual symmetric and conventional perspectives of axion electrodynamics coincide under long-wavelength approximation. Moreover, dual symmetric theory can obtain an exact analytical expression of the axion-induced electromagnetic field for any state of axion. This solution has been used in conventional theory for long-wavelength approximation. The difference between two theories can occur in directional axion detection or electric sensing haloscopes. For illustrative purposes, we consider the various type of resonant cavities: cylindrical solenoid, spherical solenoid, two-parallel-sheet cavity, toroidal solenoid with a rectangular cross-section, and with a circular cross-section. The resonance of the axion-induced signal, as well as the ratio of the energy difference over the stored energy inside the cavity, are investigated in these types of cavity.

   hep-phhep-thJCAP(2022)·2 citations
10. 10*

    Magnetic moments of spin--1/2 triply-heavy baryons: A study of Light-cone QCD and Quark-diquark model

    Halil Mutuk🇹🇷 · Ulaş Özdem🇹🇷

    In this study, the magnetic moments of the spin-1/2 triply-heavy baryons have been calculated using both light-cone QCD sum rules and Quark-diquark model. Theoretical investigations on magnetic moments of the triply-heavy baryons, are crucial as their results can help us better understand their internal structure and the dynamics of the QCD as the theory of the strong interaction. We compare the results extracted for the magnetic moment with the existing theoretical predictions. It is seen that the obtained magnetic moment values are quite compatible with the results in the literature.

    hep-phhep-exEur.Phys.J.Plus(2022)·5 citations
11. 11*

    Reshuffled Strongly Interacting Massive Particle Dark Matter

    Shu-Yu Ho🇰🇷 · Pyungwon Ko🇰🇷 · Chih-Ting Lu🇰🇷

    In this work, we reanalyze the multi-component strongly interacting massive particle (mSIMP) scenario using an effective operator approach. As in the single-component SIMP case, the total relic abundance of mSIMP dark matter (DM) is determined by the coupling strengths of $3\to 2$ processes achieved by a five-point effective operator. Intriguingly, we notice that there is an irreducible $2\to 2$ process induced by the corresponding five-point interaction in the dark sector, which would reshuffle the mass densities of SIMP DM after the chemical freeze-out. We dub this DM scenario as reshuffled SIMP ($r$SIMP). Given this observation, we then numerically solve the coupled Boltzmann equations including the $3\to 2$ and $2\to 2$ processes to get the correct yields of $r$SIMP DM. It turns out that the masses of $r$SIMP DM must be nearly degenerate for them to contribute sizable abundances. On the other hand, we also introduce effective operators to bridge the dark sector and visible sector via a vector portal coupling. Notably, we find that the reshuffled mechanism in the $r$SIMP scenario is sensitive to the size of the DM self-interacting cross section.

    hep-phastro-ph.COhep-thPhys.Dark Univ.(2022)·6 citations
12. 12*

    Top-quark decay into Upsilon-meson

    Sergei Slabospitskii🇷🇺

    The calculation of the partial width of the rare t-quark decay into Upsilon-meson, W-boson and b-quark (t -> \Upsilon W b) is presented. The branching ratio equals Br(t -> Upsilon W b) = 1.3 * 10^{-5} that make possible searches for this rare $t$-quark decay at LHC.

    hep-phPLB(2021)·1 citation
13. 13*

    Accelerating LHC phenomenology with analytic one-loop amplitudes: A C++ interface to MCFM

    John M Campbell🇺🇸 · Stefan Höche🇺🇸 · Christian T Preuss🇦🇺

    The evaluation of one-loop matrix elements is one of the main bottlenecks in precision calculations for the high-luminosity phase of the Large Hadron Collider. To alleviate this problem, a new C++ interface to the MCFM parton-level Monte Carlo is introduced, giving access to an extensive library of analytic results for one-loop amplitudes. Timing comparisons are presented for a large set of Standard Model processes. These are relevant for high-statistics event simulation in the context of experimental analyses and precision fixed-order computations.

    hep-phhep-exEPJC(2021)·22 citations
14. 14*

    Wide-angle photo- and electroproduction of pions to twist-3 accuracy

    Peter Kroll🇩🇪 · Kornelija Passek-Kumerički🇭🇷

    We investigate wide-angle photo- and electroproduction of pions within the handbag mechanism in which the ${\gamma }^{(\ast )}N\to \pi N^{\prime }$ amplitudes factorize into hard partonic subprocess amplitudes, ${\gamma }^{(\ast )}q\to \pi q^{\prime }$, and form factors representing $1/x$-moments of generalized parton distributions (GPDs). The subprocess is calculated to twist-3 accuracy taking into account the 2- and 3-body Fock components of the pion. Both components are required for achieving gauge invariance in QED and QCD. The twist-2 and twist-3 distribution amplitudes (DAs) of the pion as well as the form factors are taken from our study of ${\pi }^0$ photoproduction. Extensive results on photoproduction of charged pions are presented and compared to experiment. Predictions on electroproduction of pions as well as on spin effects are also given. As a byproduct of our analysis we also obtain the complete twist-3 subprocess amplitudes contributing to deeply-virtual electroproduction of pions.

    hep-phhep-exPRD(2021)·12 citations
15. 15*

    Sparticle Spectroscopy at LHC-Run3 and LSP Dark Matter in light of Muon g-2

    Qaisar Shafi🇺🇸 · Cem Salih Un🇹🇷

    Inspired by the latest measurement of muon g-2 by the Fermilab Experiment, we revisit a class of supersymmetric models in which non-universality at M_GUT allows us to realize relatively light sleptons in the few hundred GeV range. These sleptons provide additional contributions to muon g-2 that can be arranged to reconcile theory and experiment. The solutions compatible with the muon g-2 resolution typically predict light sleptons, charginos and neutralinos. We show how these solutions can be probed during LHC-Run3. A direct impact on the chargino mass is observed such that the chargino can be probed up to about 800 GeV during the Run3 experiments. Despite such a direct impact, it is still possible to realize lighter chargino masses which can escape detection due to the chirality mixture of the lighter slepton states. The colored squarks as well as the gluino turn out to be heavier than about 3-4 TeV if the LSP neutralino satisfies the Planck bound on the dark matter relic abundance. We highlight a variety of benchmark points and, in particular, coannihilation scenarios with dark matter candidates that will be tested in the ongoing and planned direct and indirect detection experiments. By relaxing the requirement that the LSP neutralino saturates the relic dark matter abundance, we are able to find solutions with gluino and squark masses in a range that may be accessible at LHC-Run3.

    hep-ph13 citations
16. 16*

    Stochastic gravitational-wave background from metastable cosmic strings

    Wilfried Buchmuller🇩🇪 · Valerie Domcke🇨🇭 · Kai Schmitz🇨🇭

    A metastable cosmic-string network is a generic consequence of many grand unified theories (GUTs) when combined with cosmic inflation. Metastable cosmic strings are not topologically stable, but decay on cosmic time scales due to pair production of GUT monopoles. This leads to a network consisting of metastable long strings on superhorizon scales as well as of string loops and segments on subhorizon scales. We compute for the first time the complete stochastic gravitational-wave background (SGWB) arising from all these network constituents, including several technical improvements to both the derivation of the loop and segment contributions. We find that the gravitational waves emitted by string loops provide the main contribution to the gravitational-wave spectrum in the relevant parameter space. The resulting spectrum is consistent with the tentative signal observed by the NANOGrav and Parkes pulsar timing collaborations for a string tension of G\mu ~ 10^-11...-7 and has ample discovery space for ground- and space-based detectors. For GUT-scale string tensions, G\mu ~ 10^-8...-7, metastable strings predict a SGWB in the LIGO-Virgo-KAGRA band that could be discovered in the near future.

    hep-phastro-ph.COgr-qcJCAP(2021)·132 citations
17. 17*

    Indirect dark-matter detection with MadDM v3.2 -- Lines and Loops

    Chiara Arina🇧🇪 · Jan Heisig🇧🇪 · Fabio Maltoni🇧🇪 · Daniele Massaro🇧🇪 · Olivier Mattelaer🇧🇪

    Automated tools for the computation of particle physics' processes have become the backbone of phenomenological studies beyond the standard model. Here, we present MadDM v3.2. This release enables the fully automated computation of loop-induced dark-matter annihilation processes, relevant for indirect detection observables. Special emphasis lies on the annihilation into $\gamma X$, where $X=\gamma ,Z,h$ or any new particle even under the dark symmetry. These processes lead to the sharp spectral feature of monochromatic gamma lines -- a smoking-gun signature of dark matter in our Galaxy. MadDM provides the predictions for the respective fluxes near-Earth and derives constraints from the gamma-ray line searches by Fermi-LAT and HESS. As an application, we discuss the implications for the viable parameter space of a top-philic $t$-channel mediator model and the inert doublet model.

    hep-phastro-ph.HEEPJC(2023)·28 citations
18. 18*

    Radiative corrections to $\tau \to \pi (K){\nu }_{\tau }[\gamma ]$: a reliable new physics test

    M. A. Arroyo-Ureña🇲🇽 · G. Hernández-Tomé🇲🇽 · G. López-Castro🇲🇽 · P. Roig🇲🇽 · I. Rosell🇪🇸

    The ratios $R_{\tau /P}\equiv \Gamma (\tau \to P{\nu }_{\tau }[\gamma ])/\Gamma (P\to \mu {\nu }_{\mu }[\gamma ])$ ($P=\pi ,K$) provide sensitive tests of lepton universality $\left|g_{\tau }/g_{\mu }\right|=1$ and are a useful tool for new physics searches. The radiative corrections to $R_{\tau /P}$ are computed following a large-$N_C$ expansion to deal with hadronic effects: Chiral Perturbation Theory is enlarged by including the lightest multiplets of spin-one heavy states such that the relevant Green functions are well-behaved at high energies. We find $\delta R_{\tau /\pi }=(0.18\pm 0.57)\%$ and $\delta R_{\tau /K}=(0.97\pm 0.58)\%$, which imply ${\left|g_{\tau }/g_{\mu }\right|}_{\pi }=0.9964\pm 0.0038$ and ${\left|g_{\tau }/g_{\mu }\right|}_K=0.9857\pm 0.0078$, compatible with and at $1.8\sigma$ of lepton universality, respectively. We test unitarity and bind non-standard effective interactions with the $\tau \to P{\nu }_{\tau }[\gamma ]$ decays.

    hep-phPRD(2021)·53 citations
19. 19*

    ${\delta }_{CP}$ for leptons and a new take on CP physics with the FSM

    José Bordes (1)🇪🇸 · Hong-Mo Chan (2)🇬🇧 · Sheung Tsun Tsou (3) ((1) Departament Fisica Teorica and IFIC, Centro Mixto CSIC, Universitat de Valencia, Spain, (2) Rutherford Appleton Laboratory, United Kingdom, (3) Mathematical Institute, University of Oxford, United Kingdom)🇬🇧

    A bonus of the framed standard model (FSM), constructed initially to explain the mass and mixing patterns of quarks and leptons, is asolution (without axions) of the strong CP problem by cancelling the theta-angle term ${\theta }_I$ $Tr(H^{\mu \nu }{H}_{\mu \nu }^{\ast })$ in colour by a chiral transformation on a quark zero mode which is inherent in FSM, and produces thereby a CP-violating phase in the CKM matrix similar in size to what is observed. Extending here to flavour, one finds that there are two terms proportional to $Tr(G^{\mu \nu }{G}_{\mu \nu }^{\ast })$: (a) in the action from flavour instantons with unknown coefficient, say ${\theta }_I^{\prime }$, (b) induced by the above FSM solution to the strong CP-problem with therefore known coefficient ${\theta }_C^{\prime }$. Both terms can be cancelled in the FSM by a chiral transformation on the lepton zero mode to give a Jarlskog invariant $J^{\prime }$ in the PMNS matrix for leptons of order $10^{-2}$, as is hinted by experiment. But if the term ${\theta }_I^{\prime }$ is to be cancelled by a chiral transformation in the predicted hidden sector to solve the strong CP problem therein, leaving only the term ${\theta }_C^{\prime }$ to be cancelled by the chiral transformation on leptons, then the following prediction results: $J^{\prime }\sim -0.012$ (${\delta }_{CP}^{\prime }\sim (1.11)\pi$) which is (i) of the right order, (ii) of the right sign, (iii) in the range favoured by present experiment. Together with the earlier result for quarks, this offers an attractive unified treatment of all known CP physics.

    hep-phInt.J.Mod.Phys.A(2021)·6 citations
20. 20*

    Detecting stochastic gravitational waves with binary resonance

    Diego Blas🇬🇧 · Alexander C. Jenkins🇬🇧

    LIGO and Virgo have initiated the era of gravitational-wave (GW) astronomy; but in order to fully explore GW frequency spectrum, we must turn our attention to innovative techniques for GW detection. One such approach is to use binary systems as dynamical GW detectors by studying the subtle perturbations to their orbits caused by impinging GWs. We present a powerful new formalism for calculating the orbital evolution of a generic binary coupled to a stochastic background of GWs, deriving from first principles a secularly-averaged Fokker-Planck equation which fully characterises the statistical evolution of all six of the binary's orbital elements. We also develop practical tools for numerically integrating this equation, and derive the necessary statistical formalism to search for GWs in observational data from binary pulsars and laser-ranging experiments.

    ↳ gr-qcastro-ph.COastro-ph.IMhep-phPRD(2022)·60 citations
21. 21*

    String (In)Stability Issues with Broken Supersymmetry

    J. Mourad🇫🇷 · A. Sagnotti🇮🇹

    We review the main results of our investigations motivated by the tadpole potentials of ten-dimensional strings with broken supersymmetry. While these are at best partial indications, it is hard to resist the feeling that they do capture some lessons of String Theory. For example, these very tadpole potentials lead to weak-string-coupling cosmologies that appear to provide clues on the onset of the inflation from an initial fast roll. The transition, if accessible to us, would offer a natural explanation for the lack of power manifested by the CMB at large angular scales. In addition, the same tadpole potentials can drive spontaneous compactifications to lower-dimensional Minkowski spaces at corresponding length scales. Furthermore, the cosmological solutions exhibit an intriguing "instability of isotropy" that, if taken at face value, would point to an accidental origin of compactification. Finally, symmetric static AdS x S solutions driven by the tadpole potentials also exist, but they are unstable due to mixings induced by their internal fluxes. On the other hand, the original Dudas-Mourad solution is perturbatively stable, and we have gathered some detailed evidence that instabilities induced by internal fluxes can be held under control in a similar class of weak-coupling type-IIB compactifications to Minkowski space.

    ↳ hep-thastro-ph.COgr-qchep-phLHEP(2021)·26 citations
22. 22*

    A cavity entanglement and state swapping method to accelerate the search for axion dark matter

    K. Wurtz🇨🇦 · B. M. Brubaker🇺🇸 · Y. Jiang🇺🇸 · E. P. Ruddy🇺🇸 · D. A. Palken🇺🇸 · K. W. Lehnert🇺🇸

    In cavity-based axion dark matter detectors, quantum noise remains a primary barrier to achieving the scan rate necessary for a comprehensive search of axion parameter space. Here we introduce a method of scan rate enhancement in which an axion-sensitive cavity is coupled to an auxiliary resonant circuit through simultaneous two-mode squeezing (entangling) and state swapping interactions. We show analytically that when combined, these interactions can amplify an axion signal before it becomes polluted by vacuum noise introduced by measurement. This internal amplification yields a wider bandwidth of axion sensitivity, increasing the rate at which the detector can search through frequency space. With interaction rates predicted by circuit simulations of this system, we show that this technique can increase the scan rate up to 15-fold relative to the scan rate of a detector limited by vacuum noise.

    ↳ quant-phhep-phPRX Quantum(2021)·41 citations
23. 23*

    Dynamical Chameleon Neutron Stars: stability, radial oscillations and scalar radiation in spherical symmetry

    Alexandru Dima🇮🇹 · Miguel Bezares🇮🇹 · Enrico Barausse🇮🇹

    Scalar-tensor theories whose phenomenology differs significantly from general relativity on large (e.g. cosmological) scales do not typically pass local experimental tests (e.g. in the solar system) unless they present a suitable "screening mechanism". An example is provided by chameleon screening, whereby the local general relativistic behavior is recovered in high density environments, at least in weak-field and quasi-static configurations. Here, we test the validity of chameleon screening in strong-field and highly relativistic/dynamical conditions, by performing fully non-linear simulations of neutron stars subjected to initial perturbations that cause them to oscillate or even collapse to a black hole. We confirm that screened chameleon stars are stable to sufficiently small radial oscillations, but that the frequency spectrum of the latter shows deviations from the general relativistic predictions. We also calculate the scalar fluxes produced during collapse to a black hole, and comment on their detectability with future gravitational-wave interferometers.

    ↳ gr-qcastro-ph.COastro-ph.HEhep-phPRD(2021)·27 citations
24. 24*

    The W mass and width measurement challenge at FCC-ee

    Paolo Azzurri🇮🇹

    The FCC-ee physics program will deliver two complementary top-notch precision determinations of the W boson mass, and width. The first and main measurement relies on the rapid rise of the W-pair production cross section near its kinematic threshold. This method is extremely simple and clean, involving only the selection and counting of events, in all different decay channels. An optimal threshold-scan strategy with a total integrated luminosity of $12{\mathrm{ab}}^{-1}$ shared on energy points between 157 and 163 GeV will provide a statistical uncertainty on the W mass of 0.5 MeV and on the W width of 1.2 MeV. For these measurements, the goal of keeping the impact of systematic uncertainties below the statistical precision will be demanding, but feasible. The second method exploits the W-pair final state reconstruction and kinematic fit, making use of events with either four jets or two jets, one lepton and missing energy. The projected statistical precision of the second method is similar to the first method's, with uncertainties of $\sim 0.5$ ($1$) MeV for the W mass (width), employing W-pair data collected at the production threshold and at 240-365 GeV. For the kinematic reconstruction method, the final impact of systematic uncertainties is currently less clear, in particular uncertainties connected to the modelling of the W hadronic decays. The use and interplay of Z$\gamma$ and ZZ events, reconstructed and fitted with the same techniques as the WW events, will be important for the extraction of W mass measurements with data at the higher 240 and 365 GeV energies.

    ↳ hep-exhep-phEur.Phys.J.Plus(2021)·22 citations
25. 25*

    Exploring requirements and detector solutions for FCC-ee

    Patrizia Azzi🇮🇹 · Emmanuel Perez🇨🇭

    Circular colliders have the advantage of delivering collisions to multiple interaction points, which allow different detector designs to be studied and optimized - up to four for FCC-ee. On the one hand, the detectors must satisfy the constraints imposed by the invasive interaction region layout. On the other hand, the performance of heavy-flavour tagging, of particle identification, of tracking and particle-flow reconstruction, and of lepton, jet, missing energy and angular resolution, need to match the physics programme and the exquisite statistical precision offered by FCC-ee. During the FCC feasibility study (2021-2025), benchmark physics processes will be used to determine, via appropriate simulations, the requirements on the detector performance or design that must be satisfied to ensure that the systematic uncertainties of the measurements are commensurate with their statistical precision. The usage of the data themselves, in order to reach the challenging goals on the stability and on the alignment of the detector, in particular for the programme at and around the Z peak, will also be studied. In addition, the potential for discovering very weakly coupled new particles, in decays of Z or Higgs bosons, could motivate dedicated detector designs that would increase the efficiency for reconstructing the unusual signatures of such processes. These studies are a crucial input to the further optimization of the two concepts described in the Conceptual Design Report, CLD, and IDEA, and to the development of new concepts which might actually prove to be better adapted to the FCC-ee physics programme, or parts thereof.

    ↳ hep-exhep-phEur.Phys.J.Plus(2021)·16 citations
26. 26*

    Electric Field Decay Without Pair Production: Lattice, Bosonization and Novel Worldline Instantons

    Xu-Yao Hu🇺🇸 · Matthew Kleban🇺🇸 · Cedric Yu🇺🇸

    Electric fields can spontaneously decay via the Schwinger effect, the nucleation of a charged particle-anti particle pair separated by a critical distance $d$. What happens if the available distance is smaller than $d$? Previous work on this question has produced contradictory results. Here, we study the quantum evolution of electric fields when the field points in a compact direction with circumference $L<d$ using the massive Schwinger model, quantum electrodynamics in one space dimension with massive charged fermions. We uncover a new and previously unknown set of instantons that result in novel physics that disagrees with all previous estimates. In parameter regimes where the field value can be well-defined in the quantum theory, generic initial fields $E$ are in fact stable and do not decay, while initial values that are quantized in half-integer units of the charge $E=(k/2)g$ with $k\in \mathbb{Z}$ oscillate in time from $+(k/2)g$ to $-(k/2)g$, with exponentially small probability of ever taking any other value. We verify our results with four distinct techniques: numerically by measuring the decay directly in Lorentzian time on the lattice, numerically using the spectrum of the Hamiltonian, numerically and semi-analytically using the bosonized description of the Schwinger model, and analytically via our instanton estimate.

    ↳ hep-thcond-mat.str-elhep-lathep-ph+1JHEP(2022)·4 citations
27. 27*

    Bridging the $\mu$Hz gap in the gravitational-wave landscape with binary resonance

    Diego Blas🇬🇧 · Alexander C. Jenkins🇬🇧

    Gravitational-wave (GW) astronomy is transforming our understanding of the Universe by probing phenomena invisible to electromagnetic observatories. A comprehensive exploration of the GW frequency spectrum is essential to fully harness this potential. Remarkably, current methods have left the $\mu$Hz frequency band almost untouched. Here, we show that this $\mu$Hz gap can be filled by searching for deviations in the orbits of binary systems caused by their resonant interaction with GWs. In particular, we show that laser ranging of the Moon and artificial satellites around the Earth, as well as timing of binary pulsars, may discover the first GW signals in this band, or otherwise set stringent new constraints. To illustrate the discovery potential of these binary resonance searches, we consider the GW signal from a cosmological first-order phase transition, showing that our methods will probe models of the early Universe that are inaccessible to any other near-future GW mission. We also discuss how our methods can shed light on the possible GW signal detected by NANOGrav, either constraining its spectral properties or even giving an independent confirmation.

    ↳ astro-ph.COastro-ph.IMgr-qchep-phPRL(2022)·88 citations

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