Fri·Nov 13, 2020Friday·November 13, 2020

1. 01*

   Effective field theory analysis of composite higgsino-like and wino-like thermal relic dark matter

   Ben Geytenbeek🇬🇧 · Ben Gripaios🇬🇧

   We study the effective field theory (including operators up to dimension five) of models in which dark matter is composite, consisting of either an electroweak doublet Dirac fermion (`higgsino-like dark matter') or an electroweak triplet Majorana fermion (`wino-like dark matter'). Some of the dimension-five operators in the former case cause mass splittings between the neutralino and chargino states, leading to a depleted rate of coannihilations and viable thermal relic dark matter with masses of the order of tens to hundreds of GeV rather than the usual pure higgsino thermal relic mass of 1 TeV. No such effects are found in the latter case (where the usual thermal relic mass is 3 TeV). Other operators, present for both wino- and higgsino-like dark matter, correspond to inelastic electromagnetic dipole moment interactions and annihilation through these can lead to viable models with dark matter masses up by an order of magnitude compared to the usual values.

   hep-phastro-ph.COJCAP(2021)·3 citations
2. 02*

   Three-Body Baryonic ${\bar{B}}^0\to {\Lambda }_c^{+}\bar{p}{\pi }^0$ Decay

   Shima Rafibakhsh🇮🇷 · Hossein Mehraban🇮🇷

   We study the three-body baryonic decay ${\bar{B}}^0\to {\Lambda }_c^{+}\bar{p}{\pi }^0$ based on the factorization approach. The most important Feynman diagrams for this decay mode are factorizable and non-factorizable contributions, so that the former plays the key role in the decay amplitude and the latter affects the amplitude coefficient $a_2$. We calculate the decay branching ratio for some values of $a_2$ in the range of $0.16-0.40$ and we find that the value of $a_2=0.17$ leads us to the result of $(1.50\pm 0.21)\times 10^{-4}$ which evidently agrees with the experimental result $(1.55\pm 0.17\pm 0.08)\times 10^{-4}$ reported by BABAR

   hep-ph0 citations
3. 03*

   Making the Universe at 20 MeV

   Gilly Elor🇺🇸 · Robert McGehee🇺🇸

   We present a testable mechanism of low-scale baryogenesis and dark matter production in which neither baryon nor lepton number are violated. Charged $D$ mesons are produced out-of-equilibrium at tens of MeV temperatures. The $D$ mesons quickly undergo CP-violating decays to charged pions, which then decay into dark-sector leptons without violating lepton number. To transfer this lepton asymmetry to the baryon asymmetry, the dark leptons scatter on additional dark-sector states charged under lepton and baryon number. Amusingly, this transfer proceeds without electroweak sphalerons, which are no longer active at such low scales. We present two example models which can achieve this transfer while remaining consistent with current limits. The required amount of CP violation in charged $D$ meson decays, while currently allowed, will be probed by colliders. Additionally, the relevant decays of charged pions to dark-sector leptons have been constrained by the PIENU and PSI experiments and will be further explored in upcoming experiments.

   hep-phastro-ph.COhep-exPRD(2021)·48 citations
4. 04*

   Structure of the nucleon at leading and subleading twist in the covariant parton model

   S.Bastami🇺🇸 · A.V.Efremov🇷🇺 · P.Schweitzer🇺🇸 · O.V.Teryaev🇷🇺 · P.Zavada🇨🇿

   The covariant parton model is generalized to describe quark correlators in a systematic way. Previous results are reproduced for the T-even leading-twist transverse momentum dependent parton distribution functions (TMDs), and for the first time all T-even twist-3 TMDs are evaluated in this model. We apply the approach to evaluate the fully unintegrated quark correlator which allows us to understand the model-specific relations between different TMDs. We verify the consistency of the approach, present numerical results and compare to available TMD parametrizations.

   hep-phPRD(2021)·27 citations
5. 05*

   Statistical approach to study neutrino interactions

   Q. Gani🇮🇳 · M. Hameeda🇮🇳

   Neutrino oscillation parameters can be understood in a better way by building a more complete picture of neutrino interactions. This poses a series of important theoretical and experimental challenges because of the elusive nature of neutrino and an inherent difficulty in its detection. This work is an attempt to study neutrino interactions through a purely theoretical approach using fluctuation theory. Though experiments are trying hard to shed more light on neutrino interactions, our knowledge of neutrino oscillation parameters is not precise at different energy levels. In this context, one cannot help but give a bold try to marvel at how far our theoretical frameworks can extend.

   hep-ph0 citations
6. 06*

   Softly shifting away from dark matter direct detection

   Chuan-Yang Xing🇨🇳 · Ling-Xiao Xu🇨🇳 · Shou-hua Zhu🇨🇳

   We propose soft breaking mechanism for dark matter (DM) shift symmetry in a class of composite dark matter models, where both DM and the Higgs boson arise as pseudo Nambu-Goldstone bosons from novel strong dynamics. Our mechanism is utilized to suppress the non-derivative portal coupling between the Higgs boson and DM particle, which can evade the stringent bound of current DM direct detection experiments. Otherwise this non-derivative portal coupling would naturally be at the same order of the Higgs quartic, rendering this class of models under severe crisis. For realizing soft breaking mechanism, we introduce vector-like top partners, dubbed as "softons", to restore the shift symmetry of DM in top Yukawa sector, which however is only broken by the softon masses. The portal coupling would automatically vanish as the shift-symmetry-breaking softon masses approach zero. Specifically we present a proof-of-concept model of soft breaking, based on the coset $O(6)/O(5)$ and the simplest fermion embedding, and study its DM phenomenology, where we show a large amount of novel parameter space is opened up by using the soft breaking mechanism.

   hep-phPRD(2021)·6 citations
7. 07*

   Low Energy Constraints From Absolute Neutrino Mass Observables and Lepton Flavor Violation in Left-Right Symmetric Model

   Srubabati Goswami🇮🇳 · Vishnudath K N

   We have studied the correlations among the three absolute neutrino mass observables - the effective Majorana mass ($m_{ee}$) which can be obtained from neutrinoless double beta decay, the electron neutrino mass ($m_{\beta }$) which is measured in single beta decay experiments and the sum of the light neutrino masses ($\Sigma$) which is constrained from cosmological observations, in the context of minimal left-right symmetric model. Two phenomenologically interesting cases of type-I seesaw dominance as well as type-II seesaw dominance have been considered. We have taken into account the independent constraints coming from lepton flavor violation, single $\beta$ decay, cosmology and neutrinoless double beta decay and have determined the combined allowed parameter space that can be probed in the future experiments. We have also analyzed the correlations and tensions between the different mass variables. In addition, the constraints on the masses of the heavy particles coming from lepton flavor violation and the bounds on three absolute neutrino mass observables are also determined. We show that these constraints can rule out some of the parameter space which are not probed by the collider experiments.

   hep-phPRD(2021)·5 citations
8. 08*

   Dark photon dark matter from charged inflaton

   Hassan Firouzjahi🇮🇷 · Mohammad Ali Gorji🇯🇵 · Shinji Mukohyama🇯🇵 · Borna Salehian🇮🇷

   We present a scenario of vector dark matter production during inflation containing a complex inflaton field which is charged under a dark gauge field and which has a symmetry breaking potential. As the inflaton field rolls towards the global minimum of the potential the dark photons become massive with a mass which can be larger than the Hubble scale during inflation. The accumulated energy of the quantum fluctuations of the produced dark photons gives the observed relic density of the dark matter for a wide range of parameters. Depending on the parameters, either the transverse modes or the longitudinal mode or their combination can generate the observed dark matter relic energy density.

   hep-phastro-ph.COhep-thJHEP(2021)·29 citations
9. 09*

   Higher order conserved charge fluctuations inside the mixed phase

   Roman V. Poberezhnyuk🇺🇦 · Oleh Savchuk🇩🇪 · Mark I. Gorenstein🇺🇦 · Volodymyr Vovchenko🇺🇸 · Horst Stoecker🇩🇪

   General formulas are presented for higher order cumulants of the conserved charge statistical fluctuations inside the mixed phase. As a particular example the van der Waals model in the grand canonical ensemble is used. The higher order measures of the conserved charge fluctuations up to the hyperkurtosis are calculated in a vicinity of the critical point (CP). The analysis includes both the mixed phase region and the pure phases on the phase diagram. It is shown that even-order fluctuation measures, e.g. scaled variance, kurtosis, and hyperkurtosis, have only positive values in the mixed phase, and go to infinity at the CP. For odd-order measures, such as skewness and hyperskewness, the regions of positive and negative values are found near the left and right binodals, respectively. The obtained results are discussed in a context of the event-by-event fluctuation measurements in heavy-ion collisions.

   hep-phnucl-exnucl-thPRC(2021)·10 citations
10. 10*

    Static Potential of the Standard Model and Spontaneously Broken Theories

    B. Assi🇩🇪 · B.A. Kniehl🇩🇪

    We consider the static potential in theories exhibiting spontaneous symmetry breaking. We use our findings to calculate the static potential of the Standard Model at one-loop order. We do so in both the Wilson loop and scattering amplitude approaches and discuss the limitations of the Wilson loop approach. As the field content of the SM is extensive, analogous results to ours in a large set of models is now achievable by varying the appropriate couplings and group theory factors.

    hep-ph3 citations
11. 11*

    Matching the Standard Model to Heavy-Quark Effective Theory and Nonrelativistic QCD

    B. Assi🇩🇪 · B.A. Kniehl🇩🇪 · J. Soto🇪🇸

    We find the leading electroweak corrections to the Lagrangians of heavy-quark effective theory and nonrelativistic QCD. These corrections appear in the Wilson coefficients of the two- and four-quark operators and are considered here at one-loop order through $\mathcal{O}(1/m^3)$ and $\mathcal{O}(1/m^2)$, respectively. The two-quark operators through this order include new parity violating terms, which we derive analogously to the parity preserving QCD result at one-loop order.

    hep-phNPB(2023)·6 citations
12. 12*

    Non-inertial effects on CP-violating systems

    V. M. G. Silveira🇧🇷 · C. A. Z. Vasconcellos🇧🇷 · E. G. S. Luna🇧🇷 · D. Hadjimichef🇧🇷

    An analysis of accelerated kaon decays based on the Unruh effect shows a slight decrease in a CP-violation parameter for very high accelerations, as a consequence of the previously know increase in decay rates for non-inertial systems. Its consequences on the understanding of the relation between thermal and non-inertial phenomena are briefly discussed.

    hep-phhep-thAstron.Nachr.(2021)·0 citations
13. 13*

    Ground Level Muon Flux Variation in a Cosmic Rays Simulation

    E. G. Pereira🇧🇷 · C. A. Z. Vasconcellos🇧🇷 · D. Hadjimichef🇧🇷

    The oscillatory movements of atmospheric air masses has been claimed to be the origin of the muon flux variation measured at the ground level. Using a cosmic ray toolkit (CORSIKA), we simulate cascade scenarios in a time scale of a year and show the dependence of the muon flux pattern with a proposed oscillatory model atmosphere.

    hep-phhep-exAstron.Nachr.(2021)·0 citations
14. 14*

    Charmonium decay in the C3P0 Model

    A. A. El-Hameed🇪🇬 · G. S. Hassan🇪🇬 · D. T. da Silva🇧🇷 · J. N. de Quadros🇧🇷 · D. Hadjimichef🇧🇷

    In this work, we use the $C^3{P}_0$ model to calculate the decay widths of the low lying charmonium $J^{PC}=1^{--}$ states, nominally $J/\psi (1S)$ and $\psi (2S)$, in the following common channels: $\rho \pi$, $\omega \eta$, $\omega {\eta }^{\prime }$, $K^{\ast +}{K}^{-}$, $K^{\ast 0}{\bar{K}}^0$, $\varphi \eta$, $\varphi {\eta }^{\prime }$.

    hep-phnucl-thAstron.Nachr.(2021)·0 citations
15. 15*

    Topping-up multilepton plus b-jets anomalies at the LHC with a $Z^{\prime }$ boson

    Ezequiel Alvarez🇦🇷 · Aurelio Juste🇪🇸 · Manuel Szewc🇦🇷 · Tamara Vazquez Schroeder🇨🇭

    During the last years ATLAS and CMS have reported a number of slight to mild discrepancies in signatures of multileptons plus $b$-jets in analyses such as $t\bar{t}H$, $t\bar{t}{W}^{\pm }$, $t\bar{t}Z$ and $t\bar{t}t\bar{t}$. Among them, a recent ATLAS result on $t\bar{t}H$ production has also reported an excess in the charge asymmetry in the same-sign dilepton channel with two or more $b$-tagged jets. Motivated by these tantalizing discrepancies, we study a phenomenological New Physics model consisting of a $Z^{\prime }$ boson that couples to up-type quarks via right-handed currents: $t_R{\gamma }^{\mu }{\bar{t}}_R$, $t_R{\gamma }^{\mu }{\bar{c}}_R$, and $t_R{\gamma }^{\mu }{\bar{u}}_R$. The latter vertex allows to translate the charge asymmetry at the LHC initial state protons to a final state with top quarks which, decaying to a positive lepton and a $b$-jet, provides a crucial contribution to some of the observed discrepancies. Through an analysis at a detector level, we select the region in parameter space of our model that best reproduces the data in the aforementioned $t\bar{t}H$ study, and in a recent ATLAS $t\bar{t}t\bar{t}$ search. We find that our model provides a better fit to the experimental data than the Standard Model for a New Physics scale of approximately $\sim$500 GeV, and with a hierarchical coupling of the $Z^{\prime }$ boson that favours the top quark and the presence of FCNC currents. In order to estimate the LHC sensitivity to this signal, we design a broadband search featuring many kinematic regions with different signal-to-background ratio, and perform a global analysis. We also define signal-enhanced regions and study observables that could further distinguish signal from background. We find that the region in parameter space of our model that best fits the analysed data could be probed with a significance exceeding 3 standard deviations with just the full Run-2 dataset.

    hep-phhep-exJHEP(2021)·12 citations
16. 16*

    ACROPOLIS: A generiC fRamework fOr Photodisintegration Of LIght elementS

    Paul Frederik Depta🇩🇪 · Marco Hufnagel🇩🇪 · Kai Schmidt-Hoberg🇩🇪

    The remarkable agreement between observations of the primordial light element abundances and the corresponding theoretical predictions within the standard cosmological history provides a powerful method to constrain physics beyond the standard model of particle physics (BSM). For a given BSM model these primordial element abundances are generally determined by (i) Big Bang Nucleosynthesis and (ii) possible subsequent disintegration processes. The latter potentially change the abundances due to late-time high-energy injections which may be present in these scenarios. While there are a number of public codes for the first part, no such code is currently available for the second. Here we close this gap and present ACROPOLIS, A generiC fRamework fOr Photodisintegration Of LIght elementS. The widely discussed cases of decays as well as annihilations can be run without prior coding knowledge within example programs. Furthermore, due to its modular structure, ACROPOLIS can easily be extended also to other scenarios.

    hep-phastro-ph.COJCAP(2021)·23 citations
17. 17*

    Updated BBN constraints on electromagnetic decays of MeV-scale particles

    Paul Frederik Depta🇩🇪 · Marco Hufnagel🇩🇪 · Kai Schmidt-Hoberg🇩🇪

    In this work, we revise and update model-independent constraints from Big Bang Nucleosynthesis on MeV-scale particles $\varphi$ which decay into photons and/or electron-positron pairs. We use the latest determinations of primordial abundances and extend the analysis in arXiv:1808.09324 by including all spin-statistical factors as well as inverse decays, significantly strengthening the resulting bounds in particular for small masses. For a very suppressed initial abundance of $\varphi$, these effects become ever more important and we find that even a pure 'freeze-in' abundance can be significantly constrained. In parallel to this article, we release the public code ACROPOLIS which numerically solves the reaction network necessary to evaluate the effect of photodisintegration on the final light element abundances. As an interesting application, we re-evaluate a possible solution of the lithium problem due to the photodisintegration of beryllium and find that e.g. an ALP produced via freeze-in can lead to a viable solution.

    hep-phastro-ph.COJCAP(2021)·98 citations
18. 18*

    From soft to hard radiation: the role of multiple scatterings in medium-induced gluon emissions

    Carlota Andres🇵🇹 · Fabio Dominguez🇪🇸 · Marcos Gonzalez Martinez🇪🇸

    A proper understanding of the physics of medium-induced gluon emissions is known to be of critical importance to describe the properties of strongly interacting matter under extreme conditions. In this regard, many theoretical efforts have been directed towards obtaining analytical calculations which might help us discerning the underlying physical picture and the dominant dynamics for different regimes. These analytical approaches rely on approximations whose validity is analyzed here by comparing their results with a recently developed numerical evaluation which includes all-order resummation of multiple scatterings. More specifically, by quantitatively comparing the energy spectrum and rates, we observe that three different regimes -- each with its corresponding physical picture -- emerge naturally from the equations: the high-energy regime where the emission process is dominated by a single hard scattering, the intermediate-energy regime where coherence effects among multiple scatterings become fundamental, and the low-energy regime where the dynamics is again dominated by a single scattering but where one must include the suppression factor due to the probability of not having any further scatterings (which is obtained through the resummation of virtual terms).

    hep-phnucl-thJHEP(2021)·33 citations
19. 19*

    Electroweak Vacuum Stability and the Higgs Field Relaxation via Gravitational Effects

    Mahdi Torabian🇮🇷

    The measured values of the Standard Model (SM) parameters favors a shallow metastable electroweak (EW) vacuum surrounded by a deep global AdS or a runaway Minkowski minimum. Furthermore, fine-tuning is the only explanation for the Higgs relaxing in its present local minimum. In this paper, assuming no new physics beyond the SM, we study the universal effect of gravity on the Higgs dynamics in the early universe. A generic two-parameter model is considered in which the Higgs is non-minimally coupled to a higher-curvature theory of gravity. The coupling between the Higgs field and the Weyl field in the Einstein frame has genuine predictions. In a broad region in the parameter space, the effective Higgs mass is large and it initially takes over through fast oscillations. This epoch is followed by the Weyl field slowly rolling a plateau-like potential. This framework generically predicts that the Higgs self-coupling in the EW vacuum is enhanced, compared to the SM predictions, through couplings to the gravity sector. Moreover, when the Higgs is settled in the EW vacuum, all other scalar flat directions would be lifted via gravitational effects mediated by the Weyl field.

    hep-phgr-qchep-thClass.Quant.Grav.(2020)·1 citation
20. 20*

    MARTY, a new C++ framework for automated symbolic calculations in Beyond the Standard Model physics

    G. Uhlrich🇫🇷 · F. Mahmoudi🇫🇷 · A. Arbey🇫🇷

    Theoretical calculations Beyond the Standard Model (BSM) constitute a challenge for high energy physicists, but are necessary when searching for New Physics. The predictions of a BSM scenario need to be compared with experimental data and the Standard Model values in order to identify the model that fits better what we observe in particle colliders. BSM predictions require very involved and error prone calculations of amplitudes, cross-sections and Wilson coefficients. Calculations at the one-loop level are often necessary for these quantities since some phenomenologically important processes may not occur at tree-level, such as Flavor Changing Neutral Currents (FCNC) in flavor physics that vanish at the tree-level. One-loop calculations have to be done analytically which is very time consuming and in practice rarely done for general BSM models. Here we present MARTY, a public and open-source C++ code. MARTY is the very first independent program able to calculate automatically amplitudes, squared amplitudes and Wilson coefficients at the one-loop level for general BSM models. This type of calculations requires a computer algebra system and could only be done, up to now, using Mathematica, a commercial and closed software for symbolic manipulations. MARTY does not rely on Mathematica since it re-implements its own computer algebra system also in C++, called CSL. MARTY will considerably ease BSM studies as by automating the analytical calculations the main task of the user would be the model building part. Once interfaced with other phenomenological codes in particle physics, MARTY will be incredibly efficient to make detailed predictions for general BSM models automatically.

    hep-phPoS(2021)·7 citations
21. 21*

    The Efficacy of Event Isotropy as an Event Shape Observable

    Cari Cesarotti🇺🇸 · Matthew Reece🇺🇸 · Matthew J. Strassler🇺🇸

    Event isotropy ${\mathcal{I}}^{\text{sph}}$, an event shape observable that measures the distance of a final state from a spherically symmetric state, is designed for new physics signals that are far from QCD-like. Using a new technique for producing a wide variety of signals that can range from near-spherical to jetty, we compare event isotropy to other observables. We show that thrust $T$ and the $C$ parameter (and ${\lambda }_{\text{max}}$, the largest eigenvalue of the sphericity matrix) are strongly correlated and thus redundant, to a good approximation. By contrast, event isotropy adds considerable information, often serving to break degeneracies between signals that would have almost identical $T$ and $C$ distributions. Signals with broad distributions in $T$ (or ${\lambda }_{\text{max}}$) and in ${\mathcal{I}}^{\text{sph}}$ separately often have much narrower distributions, and are more easily distinguished, in the $({\mathcal{I}}^{\text{sph}},{\lambda }_{\text{max}})$ plane. An intuitive, semi-analytic estimation technique clarifies why this is the case and assists with the interpretation of the distributions.

    hep-phJHEP(2021)·40 citations
22. 22*

    On the challenges of searching for GeV-scale long-lived particles at the LHC

    Elias Bernreuther🇩🇪 · Juliana Carrasco Mejia🇩🇪 · Felix Kahlhoefer🇩🇪 · Michael Krämer🇩🇪 · Patrick Tunney🇩🇪

    Many models of dark matter predict long-lived particles (LLPs) that can give rise to striking signatures at the LHC. Existing searches for displaced vertices are however tailored towards heavy LLPs. In this work we show that this bias severely affects their sensitivity to LLPs with masses at the GeV scale. To illustrate this point we consider two dark sector models with light LLPs that decay hadronically: a strongly-interacting dark sector with long-lived exotic mesons, and a Higgsed dark sector with a long-lived dark Higgs boson. We study the sensitivity of an existing ATLAS search for displaced vertices and missing energy in these two models and find that current track and vertex cuts result in very low efficiency for light LLPs. To close this gap in the current search programme we suggest two possible modifications of the vertex reconstruction and the analysis cuts. We calculate projected exclusion limits for these modifications and show that they greatly enhance the sensitivity to LLPs with low mass or short decay lengths.

    hep-phhep-exJHEP(2021)·16 citations
23. 23*

    The Inverse Seesaw Family: Dirac And Majorana

    Salvador Centelles Chuliá🇪🇸 · Rahul Srivastava🇮🇳 · Avelino Vicente🇪🇸

    After developing a general criterion for deciding which neutrino mass models belong to the category of inverse seesaw models, we apply it to obtain the Dirac analogue of the canonical Majorana inverse seesaw model. We then generalize the inverse seesaw model and obtain a class of inverse seesaw mechanisms both for Majorana and Dirac neutrinos. We further show that many of the models have double or multiple suppressions coming from tiny symmetry breaking "$\mu$-terms". These models can be tested both in colliders and with the observation of lepton flavour violating processes.

    hep-phJHEP(2021)·41 citations
24. 24*

    Evolution of dissipative and non-dissipative universes in holographic cosmological models with a power-law term

    Nobuyoshi Komatsu🇯🇵

    Density perturbations related to structure formations are expected to be different in dissipative and non-dissipative universes, even if the background evolution of the two universes is the same. To clarify the difference between the two universes, first-order density perturbations are studied, using two types of holographic cosmological models. The first type is a "$\Lambda (t)$ model" similar to a time-varying $\Lambda (t)$ cosmology for the non-dissipative universe. The second type is a "BV model" similar to a bulk viscous cosmology for the dissipative universe. To systematically examine the two different universes, a power-law term proportional to $H^{\alpha }$ is applied to the $\Lambda (t)$ and BV (bulk-viscous-cosmology-like) models, assuming a flat Friedmann--Robertson--Walker model for the late universe. Here, $H$ is the Hubble parameter and $\alpha$ is a free parameter whose value is a real number. The $\Lambda (t)$-$H^{\alpha }$ and BV-$H^{\alpha }$ models are used to examine first-order density perturbations for matter, in which the background evolution of the two models is equivalent. In addition, thermodynamic constraints on the two models are discussed, with a focus on the maximization of entropy on the horizon of the universe, extending previous analyses [Phys. Rev. D 100, 123545 (2019) (arXiv:1911.08306); 102, 063512 (2020) (arXiv:2006.09650)]. Consequently, the $\Lambda (t)$-$H^{\alpha }$ model for small $|\alpha |$ values is found to be consistent with observations and satisfies the thermodynamic constraints, compared with the BV-$H^{\alpha }$ model. The results show that the non-dissipative universe described by the $\Lambda (t)$-$H^{\alpha }$ model similar to lambda cold dark matter models is likely favored.

    ↳ gr-qcastro-ph.COhep-phPRD(2021)·10 citations
25. 25*

    Dense matter equation of state of a massive neutron star with anti-kaon condensation

    Vivek Baruah Thapa🇮🇳 · Monika Sinha🇮🇳

    Recent measurements of neutron star mass from several candidates (PSR J$1614-2230$, PSR J$0348+0432$, MSP J$0740+6620$) set the lower bound on the maximum possible mass for this class of compact objects $\sim 2$ M${}_{\odot }$. Existence of stars with high mass brings the possibility of existence of exotic matter (hyperons, meson condensates) at the core region of the objects. In this work, we investigate the (anti)kaon ($K^{-},{\bar{K}}^0$) condensation in $\beta -$equilibrated nuclear matter within the framework of covariant density functional theory. The functionals in the kaonic sector are constrained by the experimental studies on $K^{-}$ atomic, kaon-nucleon scattering data fits. We find that the equation of state softens with the inclusion of (anti)kaon condensates, which lowers the maximum mass of neutron star. In one of the density-independent coupling cases, the $K^{-}$ condensation is through a first-order phase transition type, which produces a $2$ M${}_{\odot }$ neutron star. The first-order phase transition results in mixed phase region in the inner core of the stars. While ${\bar{K}}^0$ condensation appears via second-order phase transition for all the models we consider here.

    ↳ astro-ph.HEhep-phPRD(2020)·57 citations
26. 26*

    Combined Lorentz symmetry: lessons from superfluid 3He

    G.E. Volovik🇫🇮

    We consider the possibility of the scenario in which the $P$, $T$ and Lorentz symmetry of the relativistic quantum vacuum are all the combined symmetries. These symmetries emerge as a result of the symmetry breaking of the more fundamental $P$, $T$ and Lorentz symmetries of the original vacuum, which is invariant under separate groups of the coordinate transformations and spin rotations. The condensed matter vacua (ground states) suggest two possible scenarios of the origin of the combined Lorentz symmetry, both are realized in the superfluid phases of liquid ${}^3$He: the ${}^3$He-A scenario and the ${}^3$He-B scenario. In these scenarios the gravitational tetrads are considered as the order parameter of the symmetry breaking in the quantum vacuum. The ${}^3$He-B scenarios applied to the Minkowski vacuum leads to the continuous degeneracy of the Minkowski vacuum with respect to the $O(3,1)$ spin rotations. The symmetry breaking leads to the corresponding topological objects, which appear due to the nontrivial topology of the manifold of the degenerate Minkowski vacua, such as torsion strings. The 4-fold degeneracy of the Minkowski vacuum with respect to discrete $P$ and $T$ symmetries suggests that the Weyl fermions are described by four different tetrad fields: the tetrad for the left-handed fermions, the tetrad for the right-handed fermions, and the tetrads for their antiparticles. This may lead to the gravity with several metric fields, so that the parity violation may lead to the breaking of equivalence principle. Finally we considered the application of the gravitational tetrads for the solution of the cosmological constant problem.

    ↳ gr-qccond-mat.otherhep-phJ.Low Temp.Phys.(2022)·11 citations
27. 27*

    Non-planar form factors of generic local operators via on-shell unitarity and color-kinematics duality

    Guanda Lin🇨🇳 · Gang Yang🇨🇳

    Form factors, as quantities involving both local operators and asymptotic particle states, contain information of both the spectrum of operators and the on-shell amplitudes. So far the studies of form factors have been mostly focused on the large Nc planar limit, with a few exceptions of Sudakov form factors. In this paper, we discuss the systematical construction of full color dependent form factors with generic local operators. We study the color decomposition for form factors and discuss the general strategy of using on-shell unitarity cut method. As concrete applications, we compute the full two-loop non-planar minimal form factors for both half-BPS operators and non-BPS operators in SU(2) sector in N=4 SYM. Another important aspect is to investigate the color-kinematics (CK) duality for form factors with high-length operators. Explicit CK dual representation is found for the two-loop half-BPS minimal form factors with arbitrary number of external legs. The full-color two-loop form factor results provide an independent check of the infrared dipole formula for two-loop n-point amplitudes. By extracting the UV divergence, we also reproduce the known two-loop non-planar SU(2) dilatation operator. As for the finite remainder function, interestingly, the non-planar part is found to contain a new maximally transcendental part beyond the known planar result.

    ↳ hep-thhep-phJHEP(2021)·29 citations
28. 28*

    Strongly-Interacting Ultralight Millicharged Particles

    Stephon Alexander🇺🇸 · Evan McDonough🇺🇸 · David N. Spergel🇺🇸

    We consider the implications of an ultra-light fermionic dark matter candidate that carries baryon number. This naturally arises if dark matter has a small charge under standard model baryon number whilst having an asymmetry equal and opposite to that in the visible universe. A prototypical model is a theory of dark baryons of a non-Abelian gauge group, i.e., a dark Quantum Chromo-Dynamics (QCD). For sub-eV dark baryon masses, the inner region of dark matter halos is naturally at 'nuclear density', allowing for the formation of exotic states of matter, akin to neutron stars. The Tremaine-Gunn lower bound on the mass of fermionic dark matter, i.e., the dark baryons, is violated by the strong short-range self-interactions, cooling via emission of light dark pions, and the Cooper pairing of dark quarks that occurs at densities that are high relative to the (ultra-low) dark QCD scale. We develop the astrophysics of these STrongly-interacting Ultra-light Millicharged Particles (STUMPs) utilizing the equation of state of dense quark matter, and find halo cores consistent with observations of dwarf galaxies. These cores are prevented from core-collapse by pressure of the 'neutron star', which suggests ultra-light dark QCD as a resolution to core-cusp problem of collisionless cold dark matter. The model is distinguished from ultra-light bosonic dark matter through direct detection and collider signatures, as well as by phenomena associated with superconductivity, such as Andreev reflection and superconducting vortices.

    ↳ astro-ph.COhep-phhep-thPLB(2021)·31 citations
29. 29*

    Opacity from Loops in AdS

    Alexandria Costantino🇺🇸 · Sylvain Fichet🇧🇷

    We investigate how quantum dynamics affects the propagation of a scalar field in Lorentzian AdS. We work in momentum space, in which the propagator admits two spectral representations (denoted "conformal" and "momentum") in addition to a closed-form one, and all have a simple split structure. Focusing on scalar bubbles, we compute the imaginary part of the self-energy $\mathrm{Im}\Pi$ in the three representations, which involves the evaluation of seemingly very different objects. We explicitly prove their equivalence in any dimension, and derive some elementary and asymptotic properties of $\mathrm{Im}\Pi$. Using a WKB-like approach in the timelike region, we evaluate the propagator dressed with the imaginary part of the self-energy. We find that the dressing from loops exponentially dampens the propagator when one of the endpoints is in the IR region, rendering this region opaque to propagation. This suppression may have implications for field-theoretical model-building in AdS. We argue that in the effective theory (EFT) paradigm, opacity of the IR region induced by higher dimensional operators censors the region of EFT breakdown. This confirms earlier expectations from the literature. Specializing to AdS${}_5$, we determine a universal contribution to opacity from gravity.

    ↳ hep-thhep-phJHEP(2021)·31 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.