Tue·Sep 29, 2020Tuesday·September 29, 2020

1. 01*

   Charting the Fifth Force Landscape

   Hannah Banks🇬🇧 · Matthew McCullough🇨🇭

   Fifth forces arising from hidden sector scalar operator exchange, as probed in a variety of present and planned experiments, can be captured by a general dispersion relation involving one real, positive, spectral density function. Previously considered scalar fifth forces, from tree-level to more exotic loop-level possibilities, are derived in this formalism, without explicitly performing conventional loop calculations. A variety of experimental observables commonly used in fifth force searches are also presented in the same formalism, allowing the straightforward extraction of limits on any specific model. The speculative possibility of probing hidden sector violations of unitarity, causality, or locality, manifested as a breakdown of the positivity of the spectral density, is also discussed.

   hep-phPRD(2021)·40 citations
2. 02*

   Revisiting Weak Radiative Decays of Hyperons

   Piotr Zenczykowski🇵🇱

   Triggered by experimentally driven renewed interest in hyperon properties we address the subject of weak radiative hyperon decays (WRHD). We start with the issue of Hara's theorem and briefly discuss the question of its possible evasion. Then, we give a short review of the story of vector-meson-dominance (VMD) approach to WRHD. We stress the shift from the Hara's-theorem-violating to Hara's-theorem-satisfying version of the VMD approach that did occur over time. Finally, spurred by a recent theoretical paper, we discuss the pole model description of WRHD, putting special attention to the issue of the contributions from the intermediate $\Lambda (1405)$ state. We point out that the measurement of the $\Lambda \to n\gamma$ decay asymmetry could resolve the encountered ambiguities and definitely answer the question of whether Hara's theorem is violated or not.

   hep-phActa Phys.Polon.B(2020)·9 citations
3. 03*

   Associated production in pp and heavy ion collisions

   Hua-Sheng Shao🇫🇷

   Associated particle production processes in pp and heavy ion collisions at the LHC are in particular interesting in the sense that they provide unique tools to study double parton scattering (DPS) mechanism. In this talk, I will first review the recent theoretical, phenomenological and experimental developments of DPS in pp collisions. Then, I will focus on the DPS studies in heavy ion collisions, and stress their roles in understanding the cold nuclear matter effects, such as the (poorly known) impact-parameter dependent nuclear parton densities.

   hep-phhep-exnucl-exnucl-thPoS(2021)·1 citation
4. 04*

   Charmed ${\Omega }_c$ weak decays into $\Omega$ in the light-front quark model

   Yu-Kuo Hsiao🇨🇳 · Ling Yang🇨🇳 · Chong-Chung Lih🇨🇳 · Shang-Yuu Tsai🇨🇳

   More than ten ${\Omega }_c^0$ weak decay modes have been measured with the branching fractions relative to that of ${\Omega }_c^0\to {\Omega }^{-}{\pi }^{+}$. In order to extract the absolute branching fractions, the study of ${\Omega }_c^0\to {\Omega }^{-}{\pi }^{+}$ is needed. In this work, we predict ${\mathcal{B}}_{\pi }\equiv \mathcal{B}({\Omega }_c^0\to {\Omega }^{-}{\pi }^{+})=(5.1\pm 0.7)\times 10^{-3}$ with the ${\Omega }_c^0\to {\Omega }^{-}$ transition form factors calculated in the light-front quark model. We also predict ${\mathcal{B}}_{\rho }\equiv \mathcal{B}({\Omega }_c^0\to {\Omega }^{-}{\rho }^{+})=(14.4\pm 0.4)\times 10^{-3}$ and ${\mathcal{B}}_e\equiv \mathcal{B}({\Omega }_c^0\to {\Omega }^{-}{e}^{+}{\nu }_e)=(5.4\pm 0.2)\times 10^{-3}$. The previous values for ${\mathcal{B}}_{\rho }/{\mathcal{B}}_{\pi }$ have been found to deviate from the most recent observation. Nonetheless, our ${\mathcal{B}}_{\rho }/{\mathcal{B}}_{\pi }=2.8\pm 0.4$ is able to alleviate the deviation. Moreover, we obtain ${\mathcal{B}}_e/{\mathcal{B}}_{\pi }=1.1\pm 0.2$, which is consistent with the current data.

   hep-phhep-exEPJC(2020)·46 citations
5. 05*

   Parity of the neutron consistent with neutron-antineutron oscillations

   Kazuo Fujikawa🇯🇵 · Anca Tureanu🇫🇮

   In the analysis of neutron-antineutron oscillations, it has been recently argued in the literature that the use of the $i{\gamma }^0$ parity $n^p(t,-\vec{x})=i{\gamma }^{0}n(t,-\vec{x})$ which is consistent with the Majorana condition is mandatory and that the ordinary parity transformation of the neutron field $n^p(t,-\vec{x})={\gamma }^{0}n(t,-\vec{x})$ has a difficulty. We show that a careful treatment of the ordinary parity transformation of the neutron works in the analysis of neutron-antineutron oscillations. Technically, the CP symmetry in the mass diagonalization procedure is important and the two parity transformations, $i{\gamma }^0$ parity and ${\gamma }^0$ parity, are compensated for by the Pauli-Gürsey transformation. Our analysis shows that either choice of the parity gives the correct results of neutron-antineutron oscillations if carefully treated.

   hep-phhep-thPRD(2021)·5 citations
6. 06*

   munuSSM: A python package for the $\mu$-from-$\nu$ Supersymmetric Standard Model

   Thomas Biekötter🇩🇪

   We present the public python package munuSSM that can be used for phenomenological studies in the context of the $\mu$-from-$\nu$ Supersymmetric Standard Model ($\mu \nu$SSM). The code incorporates the radiative corrections to the neutral scalar potential at the full one-loop level. Sizable higher-order corrections, required for an accurate prediction of the SM-like Higgs-boson mass, can be consistently included via an automated link to the public code FeynHiggs. In addition, a calculation of effective couplings and branching ratios of the neutral and charged Higgs bosons is implemented. This provides the required ingredients to check a benchmark point against collider constraints from searches for additional Higgs bosons via an interface to the public code HiggsBounds. At the same time, the signal rates of the SM-like Higgs boson can be tested applying the experimental results implemented in the public code HiggsSignals. The python package is constructed in a flexible and modular way, such that it provides a simple framework that can be extended by the user with further calculations of observables and constraints on the model parameters.

   hep-phComput.Phys.Commun.(2021)·10 citations
7. 07*

   Impact of LHC Higgs couplings measurements on bosonic decays of the neutral Higgs sector in the scNMSSM

   Marwa Telba🇸🇦 · Maien Binjonaid🇸🇦

   We analyze the Next-to-minimal supersymmetric standard model with Grand unification boundary conditions under current theoretical and experimental constraints. We compute the mass spectrum of the model and focus on the three lightest particles in the Higgs sector (two CP-even scalars, $h_1,h_2$, and one CP-odd, $a_1$). The reduced couplings of such particles, singlet-doublet components, their branching ratios to bosons, and reduced cross-section to photons and massive gauge bosons via gluon fusion are thoroughly and systematically scrutinized. Our analysis is focused on the parameter space where the singlet-doublet coupling $\lambda$ is as large as possible (keeping the perturbativity bound intact) and the ratio between the vacuum expectation values of the up-type and down-type Higgses ($\tan \beta$) is as small as possible, which is the region representing the most natural case of the NMSSM. We show the impact of recent constraints from the LHC on the SM-Higgs couplings to bosons and fermions on the parameter space of the model and the consequent implications on the Higgs sector. The results show that while the model is still able to account for current data and provide an opportunity for discovery of extended Higgs sectors, recent LHC Higgs couplings constraints rule-out parts of the parameter space where $h_2$ (non-SM-like) and $a_1$ are non-singlet with masses below ~400 GeV.

   hep-phMod.Phys.Lett.A(2021)·2 citations
8. 08*

   Inflation and DM phenomenology in a scotogenic model extended with a real singlet scalar

   Tsuyoshi Hashimoto🇯🇵 · Daijiro Suematsu🇯🇵

   We study an extension of the scotogenic model with a real singlet scalar. It gives an origin of the mass of right-handed neutrinos and plays a role of inflaton through a non-minimal coupling with Ricci scalar. While an inert doublet scalar is an indispensable ingredient for neutrino mass generation in the model, it is also a promising dark matter (DM) candidate. Introduction of the singlet scalar could affect its nature of DM if mass of the singlet scalar is in a resonance region. We focus our study on such a case where inflaton mass is expected to be in a TeV range and reheating temperature is less than $10^9$ GeV. Thus the model requires low scale leptogenesis. After examining several effects brought about by the singlet scalar for the DM sector, we discuss DM phenomenology such as high energy neutrinos and monochromatic gammas caused by its annihilation.

   hep-phPRD(2020)·10 citations
9. 09*

   High-Energy Factorization for Drell-Yan process in $pp$ and $p\bar{p}$ collisions with new Unintegrated PDFs

   Maxim A. Nefedov🇷🇺 · Vladimir A. Saleev🇷🇺

   The formalism for uniform description of Drell-Yan transverse-momentum spectrum is presented in a framework of High-Energy Factorization, which smoothly interpolates between Collins-Soper-Sterman formalism at $|{\mathbf{q}}_T|\ll Q$ and usual Collinear Parton Model at $|{\mathbf{q}}_T|\sim Q\ll \sqrt{S}$. The new formula for deriving Unintegrated Parton Distribution Functions(UPDFs) from collinear ones is introduced, which leads to excellent description of the shape of $Z$-boson $|{\mathbf{q}}_T|$-spectrum at high energies up to $|{\mathbf{q}}_T|/\sqrt{S}\simeq 0.02$. Description of normalized $|{\mathbf{q}}_T|$-distributions at low energies is achieved via the fit of non-perturbative parameters of quark UPDFs. Reasonable description of angular distributions of leptons in the dilepton center-of-mass frame is also obtained with new UPDFs.

   hep-phPRD(2020)·35 citations
10. 10*

    Off-shell effects in $t\bar{t}+\gamma /Z$ production at the LHC

    Giuseppe Bevilacqua🇭🇺

    We present state-of-the-art predictions for $t\bar{t}\gamma$ and $t\bar{t}Z(Z\to {\nu }_{\ell }{\bar{\nu }}_{\ell })$ production in the fully leptonic channel at the LHC. The first process can provide key information on the strength and structure of the top-quark coupling to the photon. The invisible-decay channel $t\bar{t}Z(Z\to {\nu }_{\ell }{\bar{\nu }}_{\ell })$ is an important SM background for Dark Matter searches in $t\bar{t}+E_T^{miss}$ final states. Our results are accurate to NLO in QCD and include all resonant and non-resonant diagrams, interferences and off-shell effects for top quarks and $W/Z$ bosons. As such, they represent the most complete description of these processes from the viewpoint of a fixed-order calculation. We show selected results for the LHC Run II energy of 13 TeV, focusing on the impact of choosing well motivated scales and on the effect of using different approaches for the modeling of top quark decays.

    hep-phPoS(2021)·0 citations
11. 11*

    Masses of the $QQ\bar{Q}\bar{Q}$ tetraquarks in the relativistic diquark--antidiquark picture

    R.N. Faustov🇷🇺 · V.O. Galkin🇷🇺 · E.M. Savchenko🇷🇺

    Masses of the ground-state teraquarks composed from heavy $c$ and $b$ quarks and antiquarks are calculated in the diquark-antidiquark picture in the framework of the relativistic quark model based on the quasipotential approach. The quasipotentials of the quark-quark and diquark-antidiquark interactions are constructed similarly to the previous consideration of mesons and baryons. It is assumed that the diquark and antidiquark interact in the tetraquark as a whole and the internal structure of the diquarks is taken into account. All such tetraquarks are found above the thresholds of decays to two heavy quarkonia. This is a result of the consideration of the diquark not to be a point-like object. Therefore such tetraquarks can be observed as broad structures decaying dominantly to quarkonia. The broad structure next to the di-$J/\psi$ mass threshold, recently observed by the LHCb Collaboration, can correspond to the ground $2^{++}$-state tetraquark consisting of four charm quarks.

    hep-phhep-exPRD(2020)·100 citations
12. 12*

    An Analytical Solution of the Balitsky-Kovchegov Equation with the Homogeneous Balance Method

    Xiaopeng Wang🇨🇳 · Yirui Yang🇨🇳 · Wei Kou🇨🇳 · Rong Wang🇨🇳 · Xurong Chen🇨🇳

    Nonlinear QCD evolution equations are essential tools in understanding the saturation of partons at small Bjorken $x_{\mathrm{B}}$, as they are supposed to restore an upper bound of unitarity for the cross section of high energy scattering. In this paper, we present an analytical solution of Balitsky-Kovchegov (BK) equation using the homogeneous balance method. The obtained analytical solution is similar to the solution of a traveling wave. By matching the gluon distribution in the dilute region which is determined from the global analysis of experimental data (CT14 analysis), we get a definitive solution of the dipole-proton forward scattering amplitude in the momentum space. Based on the acquired scattering amplitude and the behavior of geometric scaling, we present also a new estimated saturation scale $Q_s^2(x)$.

    hep-phPRD(2021)·12 citations
13. 13*

    Gauge invariance of quantum electrodynamics of multi-electron atoms

    M. I. Krivoruchenko🇷🇺

    The proof of gauge invariance of the quantum electrodynamics of photons and electrons does not apply directly to the quantum electrodynamics of photons, electrons, and nuclei because multi-electron atoms belong to the space of asymptotic states of the extended theory. We offer two possible ways to circumvent this problem and prove, using a fairly general model for the description of nucleon-nucleon interaction in nuclei, the gauge invariance of the masses and electromagnetic form factors of multi-electron atoms in all orders of perturbation theory.

    hep-phphysics.atom-phPhys.Atom.Nucl.(2023)·1 citation
14. 14*

    ATLAS Violating CP Effectively

    Supratim Das Bakshi🇮🇳 · Joydeep Chakrabortty🇮🇳 · Christoph Englert🇬🇧 · Michael Spannowsky🇬🇧 · Panagiotis Stylianou🇬🇧

    CP violation beyond the Standard Model (SM) is a crucial missing piece for explaining the observed matter-antimatter symmetry in the Universe. Recently, the ATLAS experiment at the Large Hadron Collider has performed an analysis of electroweak $Zjj$ production, thereby excluding the SM locally at 95\% confidence level in the measurement of CP-sensitive observables. We take the excess' interpretation in terms of anomalous gauge-Higgs interactions at face value and discuss further steps that are required to scrutinize its origin. In particular, we discuss the relevance of multi-boson production using adapted angular observables to show how they can be used to directly tension the reported $Zjj$ excess in a more comprehensive analysis. To connect the excess to a concrete UV scenario for which the underlying assumptions of the $Zjj$ analysis are valid, we identify vector-like leptons as a candidate theory consistent with the observed CP-odd Wilson coefficient hierarchy observed by ATLAS. We perform a complete one-loop matching calculation to motivate further model-specific and correlated new physics searches. In parallel, we provide estimates of the sensitivity reach of the LHC's high luminosity phase for this particular scenario of CP-violation in light of electroweak precision and Run-2 Higgs data. These provide strong constraints on the model's CP-even low-energy phenomenology, but also inform the size of the CP-odd SM deformation indirectly via our model hypothesis.

    hep-phhep-exPRD(2021)·36 citations
15. 15*

    Chemical freeze-out systematics of thermal model analysis using hadron yield ratios

    Sumana Bhattacharyya🇮🇳 · Amaresh Jaiswal🇮🇳 · Sutanu Roy🇮🇳

    We provide a framework to estimate the systematic uncertainties in chemical freeze-out parameters extracted from ${\chi }^2$ analysis of thermal model, using hadron multiplicity ratios in relativistic heavy-ion collision experiments. Using a well known technique of graph theory, we construct all possible sets of independent ratios from available hadron yields and perform ${\chi }^2$ minimization on each set. We show that even for ten hadron yields, one obtains a large number ($10^8$) of independent sets which results in a distribution of extracted freeze-out parameters. We analyze these distributions and compare our results for chemical freeze-out parameters and associated systematic uncertainties with previous results available in the literature.

    hep-phhep-exnucl-thPRC(2021)·6 citations
16. 16*

    Sommerfeld Enhancements for Asymmetric Dark Matter

    Aerman Sulitan🇨🇳 · Hoernisa Iminniyaz🇨🇳 · Mu Baoxia🇨🇳

    We extend the analysis of asymmetric Dark Matter relic density with Sommerfeld enhancement to the case where the mediator is massive. In asymmetric Dark Matter models, the asymmetric Dark Matter is assumed to couple to light scalar or vector boson. Asymmetric Dark Matter annihilation cross section is enhanced by the Sommerfeld effect which exists due to the distortion of wavefunction of asymmetric Dark Matter particle and anti--particle by long--range interactions. The impacts of Sommerfeld enhancement on the relic densities of asymmetric Dark Matter particle and anti--particle are discussed. The effect of kinetic decoupling on the relic density is also probed when the annihilation cross section is enhanced by Sommerfeld enhancement. Finally, the constraints on the parameter space is given by using the observational data of Dark Matter.

    hep-phChin.J.Phys.(2021)·1 citation
17. 17*

    Polarization as a signature of local parity violation in hot QCD matter

    F. Becattini (Univeristy of Florence)🇮🇹 · M. Buzzegoli (Iowa State U.)🇮🇹 · A. Palermo (University of Florence)🇮🇹 · G. Prokhorov (JINR, Dubna)🇷🇺

    We show that local parity violation due to chirality imbalance in relativistic nuclear collisions can be revealed by measuring the projection of the polarization vector onto the momentum, i.e. the helicity, of final state baryons. The proposed method does not require a coupling to the electromagnetic field, like in the Chiral Magnetic Effect. By using linear response theory, we show that, in the presence of a chiral imbalance, the spin 1/2 baryons and anti-baryons receive an additional contribution to the polarization along their momentum and proportional to the axial chemical potential. The additional, parity-breaking, contribution to helicity can be detected by studying helicity-helicity azimuthal angular correlation.

    hep-phnucl-thPLB(2021)·22 citations
18. 18*

    Gravitational wave complementarity and impact of NANOGrav data on gravitational leptogenesis: cosmic strings

    Rome Samanta🇬🇧 · Satyabrata Datta🇮🇳

    In seesaw mechanism, if right handed (RH) neutrino masses are generated dynamically by a gauged $U(1)$ symmetry breaking, a stochastic gravitational wave background (SGWB) sourced by a cosmic string network could be a potential probe of leptogenesis. We show that the leptogenesis mechanism that facilitates the dominant production of lepton asymmetry via the quantum effects of right-handed neutrinos in gravitational background, can be probed by GW detectors as well as next-generation neutrinoless double beta decay ($0\nu \beta \beta$) experiments in a complementary way. We infer that for a successful leptogenesis, an exclusion limit on $f-{\Omega }_{\mathrm{GW}}{h}^2$ plane would correspond to an exclusion on the $|m_{\beta \beta }|-m_1$ plane as well. We consider a normal light neutrino mass ordering and discuss how recent NANOGrav pulsar timing data (if interpreted as GW signal) e.g., at 95$\%$ CL, would correlate with the potential discovery or null signal in $0\nu \beta \beta$ decay experiments.

    hep-phastro-ph.COastro-ph.GAgr-qcJHEP(2021)·126 citations
19. 19*

    Neutrino Decoherence in Simple Open Quantum Systems

    Bin Xu🇺🇸

    Neutrinos lose coherence as they propagate, which leads to the fading away of oscillations. In this work, we model neutrino decoherence induced in open quantum systems from their interaction with the environment. We first present two different models in the quantum mechanical framework, in which the environment is modeled as forced harmonic oscillators with white noise interactions, or two-level systems with stochastic phase kicks. We then look at the decoherence process in the quantum field theoretic framework induced by elastic scatterings with environmental particles. The exponential decay is obtained as a common feature for all models, which shows the universality of the decoherence processes. We discuss connections to the GKSL master equation approach and give a clear physical meaning of the Lindblad operators. We demonstrate that the universality of exponential decay of coherence is based on the Born-Markov approximation. The models in this work are suitable to be extended to describe real physical processes that could be non-Markovian.

    hep-phhep-thquant-ph6 citations
20. 20*

    Radiative seesaw corrections and charged-lepton decays in a model with soft flavour violation

    E.H. Aeikens🇦🇹 · P.M. Ferreira🇵🇹 · W. Grimus🇦🇹 · D. Jurčiukonis🇱🇹 · L. Lavoura🇵🇹

    We consider the one-loop radiative corrections to the light-neutrino mass matrix and their consequences for the predicted branching ratios of the five lepton-flavour-violating decays ${\ell }_1^{-}\to {\ell }_2^{-}{\ell }_3^{+}{\ell }_3^{-}$ in a two-Higgs-doublet model furnished with the type-I seesaw mechanism and soft lepton-flavour violation. We find that the radiative corrections are very significant; they may alter the predicted branching ratios by several orders of magnitude and, in particular, they may help explain why $\text{mbox}BR({\mu }^{-}\to e^{-}{e}^{+}{e}^{-})$ is strongly suppressed relative to the branching ratios of the decays of the ${\tau }^{-}$. We conclude that, in any serious numerical assessment of the predictions of this model, it is absolutely necessary to take into account the one-loop radiative corrections to the light-neutrino mass matrix.

    hep-phJHEP(2020)·2 citations
21. 21*

    A Review on Partial-wave Dynamics with Chiral Effective Field Theory and Dispersion Relation

    De-Liang Yao🇨🇳 · Ling-Yun Dai🇨🇳 · Han-Qing Zheng🇨🇳 · Zhi-Yong Zhou🇨🇳

    The description of strong interaction physics of low-lying resonances is out of the valid range of perturbative QCD. Chiral effective field theories have been developed to tackle the issue. Partial wave dynamics is the systematic tool to decode the underlying physics and reveal the properties of those resonances. It is extremely powerful and helpful for our understanding of the non-perturbative regime, especially when dispersion techniques are utilized simultaneously. Recently, plenty of exotic/ordinary hadrons have been reported by experiment collaborations, e.g. LHCb, Belle, and BESIII, etc.. In this review, we summarize the recent progress on the applications of partial wave dynamics combined with chiral effective field theories and dispersion relations, on related topics, with emphasis on $\pi \pi$, $\pi K$, $\pi N$ and $\bar{K}N$ scatterings.

    hep-phnucl-thRept.Prog.Phys.(2021)·91 citations
22. 22*

    Resummed predictions for hadronic Higgs boson decays

    Simone Alioli🇮🇹 · Alessandro Broggio🇮🇹 · Alessandro Gavardi🇮🇹 · Stefan Kallweit🇮🇹 · Matthew A. Lim🇮🇹 · Riccardo Nagar🇮🇹 · Davide Napoletano🇮🇹 · Luca Rottoli🇮🇹

    We present the NNLL${}^{\prime }$ resummed $2$-jettiness distribution for decays of the Standard Model Higgs boson to a $b\bar{b}$-quark pair and to gluons. The calculation exploits a factorisation formula derived using Soft-Collinear Effective Theory, in which large logarithms of the $2$-jettiness are resummed by renormalisation group evolution of the hard, soft and jet contributions to the differential decay rate. We match the resummed predictions to the fixed-order NNLO result using the GENEVA framework, extending the validity of the results to all values of the resolution variable and providing a fully exclusive NNLO event generator matched to the PYTHIA8 parton shower.

    hep-phhep-exJHEP(2021)·44 citations
23. 23*

    Effective Field Theory of Dark Matter Direct Detection With Collective Excitations

    Tanner Trickle🇺🇸 · Zhengkang Zhang🇺🇸 · Kathryn M. Zurek🇺🇸

    We develop a framework for computing light dark matter direct detection rates through single phonon and magnon excitations via general effective operators. Our work generalizes previous calculations focused on spin-independent interactions involving the total nucleon and electron numbers $N$ (the usual route to excite phonons) and spin-dependent interactions involving the total electron spin $S$ (the usual route to excite magnons), leading us to identify new responses involving the orbital angular momenta $L$, as well as spin-orbit couplings $L\otimes S$ in the target. All four types of responses can excite phonons, while couplings to electron's $S$ and $L$ can also excite magnons. We apply the effective field theory approach to a set of well-motivated relativistic benchmark models, including (pseudo-)scalar mediated interactions, and models where dark matter interacts via a multipole moment, such as a dark electric dipole, magnetic dipole or anapole moment. We find that couplings to point-like degrees of freedom $N$ and $S$ often dominate dark matter detection rates, implying that exotic materials with orbital $L$ order or large spin-orbit couplings $L\otimes S$ are not necessary to have strong reach to a broad class of DM models. We highlight that phonon based crystal experiments in active R&D (such as SPICE) will probe light dark matter models well beyond those having a simple spin-independent interaction, including e.g. models with dipole and anapole interactions. Lastly, we make publicly available a code, PhonoDark, which computes single phonon production rates in a wide variety of materials with the effective field theory framework.

    hep-phastro-ph.COPRD(2022)·95 citations
24. 24*

    Exploding operators for Majorana neutrino masses and beyond

    John Gargalionis🇦🇺 · Raymond R. Volkas🇦🇺

    Building UV completions of lepton-number-violating effective operators has proved to be a useful way of studying and classifying models of Majorana neutrino mass. In this paper we describe and implement an algorithm that systematises this model-building procedure. We use the algorithm to generate computational representations of all of the tree-level completions of the operators up to and including mass-dimension 11. Almost all of these correspond to models of radiative neutrino mass. Our work includes operators involving derivatives, updated estimates for the bounds on the new-physics scale associated with each operator, an analysis of various features of the models, and a look at some examples. We find that a number of operators do not admit any completions not also generating lower-dimensional operators or larger contributions to the neutrino mass, ruling them out as playing a dominant role in the neutrino-mass generation. Additionally, we show that there are at most five models containing three or fewer exotic multiplets that predict new physics that must lie below 100 TeV. Accompanying this work we also make available a searchable database containing all of our results and the code used to find the completions. We emphasise that our methods extend beyond the study of neutrino-mass models, and may be useful for generating completions of high-dimensional operators in other effective field theories.

    hep-phJHEP(2021)·44 citations
25. 25*

    QFT treatment of a bound state in a thermal gas

    Subhasis Samanta🇵🇱 · Francesco Giacosa🇵🇱

    We investigate how to include bound states in a thermal gas in the context of quantum field theory (QFT). To this end, we use for definiteness a scalar QFT with a ${\phi }^4$ interaction, where the field $\phi$ represents a particle with mass $m$. A bound state of the $\phi$-$\phi$ type is created when the coupling constant is negative and its modulus is larger than a certain critical value. We investigate the contribution of this bound state to the pressure of the thermal gas of the system by using the $S$-matrix formalism involving the derivative of the phase-shift scattering. Our analysis, which is based on an unitarized one-loop resumed approach which renders the theory finite and well-defined for each value of the coupling constant, leads to following main results: (i) We generalize the phase-shift formula in order to take into account within a unique formal approach the two-particle interaction as well as the bound state (if existent). (ii) \textit{On the one hand}, the number density of the bound state in the system at a certain temperature $T$ is obtained by the standard thermal integral; this is the case for any binding energy, even if it is much smaller than the temperature of the thermal gas. (iii) \textit{On the other hand}, the contribution of the bound state to the total pressure is partly -- but not completely -- canceled by the two-particle interaction contribution to the pressure. (iv) The pressure as function of the coupling constant is \textit{continuous} also at the critical coupling for the bound state formation: the jump in pressure due to the sudden appearance of the bound state is exactly canceled by an analogous jump (but with opposite sign) of the interaction contribution to the pressure.

    hep-phhep-thPRD(2021)·10 citations
26. 26*

    Quantum Fluctuations and New Instantons II: Quartic Unbounded Potential

    Viatcheslav Mukhanov🇩🇪 · Eliezer Rabinovici🇮🇱 · Alexander Sorin🇷🇺

    We study the fate of a false vacuum in the case of a potential that contains a portion which is quartic and unbounded. We first prove that an $O(4)$ invariant instanton with the Coleman boundary conditions does not exist in this case. This, however, does not imply that the false vacuum does not decay. We show how the quantum fluctuations may regularize the singular classical solutions. This gives rise to a new class of $O(4)$ invariant regularized instantons which describe the vacuum instability in the absence of the Coleman instanton. We derive the corresponding solutions and calculate the decay rate they induce.

    ↳ hep-thgr-qchep-phquant-phFortsch.Phys.(2021)·11 citations
27. 27*

    Quantum Fluctuations and New Instantons I: Linear Unbounded Potential

    Viatcheslav Mukhanov🇰🇷 · Eliezer Rabinovici🇮🇱 · Alexander Sorin🇷🇺

    We consider the decay of a false vacuum in circumstances where the methods suggested by Coleman run into difficulties. We find that in these cases quantum fluctuations play a crucial role. Namely, they naturally induce both an ultraviolet and infrared cutoff scales, determined by the parameters of the classical solution, beyond which this solution cannot be trusted anymore. This leads to the appearance of a broad class of new $O(4)$ invariant instantons, which would have been singular in the absence of an ultraviolet cutoff. We apply our results to a case where the potential is unbounded from below in a linear way and in particular show how the problem of small instantons is resolved by taking into account the inevitable quantum fluctuations.

    ↳ hep-thgr-qchep-phquant-phFortsch.Phys.(2021)·10 citations
28. 28*

    A fake Interacting Dark Energy detection?

    Eleonora Di Valentino🇬🇧 · Olga Mena🇪🇸

    Models involving an interaction between the Dark Matter and the Dark Energy sectors have been proposed to alleviate the long standing Hubble constant tension. In this paper we analyze whether the constraints and potential hints obtained for these interacting models remain unchanged when using simulated Planck data. Interestingly, our simulations indicate that a dangerous fake detection for a non-zero interaction among the Dark Matter and the Dark Energy fluids could arise when dealing with current CMB Planck measurements alone. The very same hypothesis is tested against future CMB observations, finding that only cosmic variance limited polarization experiments, such as PICO or PRISM, could be able to break the existing parameter degeneracies and provide reliable cosmological constraints. This paper underlines the extreme importance of confronting the results arising from data analyses with those obtained with simulations when extracting cosmological limits within exotic cosmological scenarios.

    ↳ astro-ph.COgr-qchep-phMNRAS(2020)·57 citations
29. 29*

    Entanglement entropy of cosmological perturbations for S-brane Ekpyrosis

    Suddhasattwa Brahma🇨🇦 · Robert Brandenberger🇨🇦 · Ziwei Wang (McGill University)🇨🇦

    We calculate the entanglement entropy of scalar perturbations due to gravitational non-linearities present in any model of canonically-coupled, single-field ekpyrosis. Specifically, we focus on a recent model of improved ekpyrosis which is able to generate a scale-invariant power spectrum of curvature perturbations and gravitational waves as well as have a non-singular bounce due to an S-brane at the end of ekpyrotic contraction. By requiring that the entanglement entropy remians subdominant to the thermal entropy produced during reheating, we get an upper bound on the energy scale of the bounce.

    ↳ hep-thastro-ph.COgr-qchep-phJCAP(2021)·3 citations
30. 30*

    Cosmological signatures of a Rapid Diluted Energy Density

    Axel de la Macorra🇲🇽 · Dante V. Gomez-Navarro🇲🇽 · Alejandro Aviles🇲🇽 · Mariana Jaber🇵🇱 · Jorge Mastache🇲🇽 · Erick Almaraz🇿🇦

    We study the cosmological signatures of having extra energy density, ${\rho }_{ex}$, beyond the $\Lambda$CDM model that dilutes rapidly, faster than radiation, at a scale factor $a_c$ with a corresponding mode $k_c=a_{c}H(a_c)$ crossing the horizon at that time. These types of models are motivated by phase transitions of the underlying elementary particles, for example the creation of protons and neutrons from almost massless quarks or the recently proposed Bound Dark Energy model. The rapidly dilution of ${\rho }_{ex}$ leaves distinctive imprints in the Universe not only in the expansion history with a clear impact on the acoustic scale, $r_s(a_{c}c)$, and angular distances, $D_A(a)$, but also in the matter and CMB power spectra. The rapidly diluted energy density ${\rho }_{ex}$, (RDED) generates characteristic signatures that can be observed with current and future precision cosmological data. In particular, we find a bump in the matter power spectrum compared to the standard $\Lambda$CDM. We identify the amplitude, width, and time scale of the bump to the physical properties of the transition. We study these effects with linear theory, standard perturbation theory, and the correlated impact on cosmological distances, allowing for independent measurements of these extensions of the standard $\Lambda$CDM model.

    ↳ astro-ph.COastro-ph.GAhep-phPRD(2021)·5 citations
31. 31*

    Cosmological constraints from higher-redshift gamma-ray burst, HII starburst galaxy, and quasar (and other) data

    Shulei Cao🇺🇸 · Joseph Ryan🇺🇸 · Narayan Khadka🇺🇸 · Bharat Ratra🇺🇸

    We use higher-redshift gamma-ray burst (GRB), HII starburst galaxy (HIIG), and quasar angular size (QSO-AS) measurements to constrain six spatially flat and non-flat cosmological models. These three sets of cosmological constraints are mutually consistent. Cosmological constraints from a joint analysis of these data sets are largely consistent with currently-accelerating cosmological expansion as well as with cosmological constraints derived from a combined analysis of Hubble parameter ($H(z)$) and baryon acoustic oscillation (BAO, with Planck-determined baryonic matter density) measurements. A joint analysis of the $H(z)$ + BAO + QSO-AS + HIIG + GRB data provides fairly model-independent determinations of the non-relativistic matter density parameter ${\Omega }_{{\mathrm{m}}_0}=0.313\pm 0.013$ and the Hubble constant $H_0=69.3\pm 1.2\mathrm{km}{\mathrm{s}}^{-1}\mathrm{Mp}{\mathrm{c}}^{-1}$. These data are consistent with the dark energy being a cosmological constant and with spatial hypersurfaces being flat, but they do not rule out mild dark energy dynamics or a little spatial curvature. We also investigate the effect of including quasar flux measurements in the mix and find no novel conclusions.

    ↳ astro-ph.COgr-qchep-phhep-thMNRAS(2021)·59 citations
32. 32*

    Flavor decomposition for the proton helicity parton distribution functions

    C. Alexandrou (Univ. of Cyprus & The Cyprus Inst.)🇨🇾 · M. Constantinou (Temple Univ.)🇺🇸 · K. Hadjiyiannakou (Univ. of Cyprus)🇨🇾 · K. Jansen (DESY-Zeuthen)🇩🇪 · F. Manigrasso (Univ. of Cyprus, Humboldt Univ., Univ. of Rome Tor Vergata)🇨🇾

    We present, for the first time, an \textit{ab initio} calculation of the individual up, down and strange quark helicity parton distribution functions for the proton. The calculation is performed within the twisted mass clover-improved fermion formulation of lattice QCD using one ensemble of dynamical up, down, strange and charm quarks with a pion mass of 260 MeV. The lattice matrix elements are non-perturbatively renormalized and the final results are presented in the $\overline{\mathrm{MS}}$ scheme at a scale of 2 GeV. We give results on the $\Delta u^{+}(x)$ and $\Delta d^{+}(x)$, including disconnected quark loop contributions, as well as on the $\Delta s^{+}(x)$. For the latter we achieve unprecedented precision compared to the phenomenological estimates.

    ↳ hep-lathep-phnucl-thPRL(2021)·51 citations
33. 33*

    Implications of the NANOGrav results for inflation

    Sunny Vagnozzi🇬🇧

    The NANOGrav pulsar timing array experiment reported evidence for a stochastic common-spectrum process affecting pulsar timing residuals in its 12.5-year dataset, which might be interpreted as the first detection of a stochastic gravitational wave background (SGWB). I examine whether the NANOGrav signal might be explained by an inflationary SGWB, focusing on the implications for the tensor spectral index $n_T$ and the tensor-to-scalar ratio $r$. Explaining NANOGrav while complying with upper limits on $r$ from BICEP2/Keck Array and Planck requires $r\gtrsim \mathcal{O}(10^{-6})$ in conjunction with an extremely blue tensor spectrum, $0.7\lesssim n_T\lesssim 1.3$. After discussing models which can realize such a blue spectrum, I show that this region of parameter space can be brought in agreement with Big Bang Nucleosynthesis constraints for a sufficiently low reheating scale, $T_{\mathrm{rh}}\lesssim 100\mathrm{GeV}-1\mathrm{TeV}$. With the important caveat of having assumed a power-law parametrization for the primordial tensor spectrum, an inflationary interpretation of the NANOGrav signal is therefore not excluded.

    ↳ astro-ph.COgr-qchep-phhep-thMNRAS(2021)·246 citations
34. 34*

    Phase diagram of alpha matter with Skyrme-like scalar interaction

    Leonid M. Satarov🇩🇪 · Roman V. Poberezhnyuk🇺🇦 · Igor N. Mishustin🇩🇪 · Horst Stoecker🇩🇪

    The equation of state and phase diagram of strongly interacting matter composed of $\alpha$ particles are studied in the mean-field approximation. The particle interactions are included via a Skyrme-like mean field, containing both attractive and repulsive terms. The model parameters are found by fitting known values of binding energy and baryon density in the ground state of $\alpha$ matter, obtained from microscopic calculations by Clark and Wang. Thermodynamic quantities of $\alpha$ matter are calculated in the broad domains of temperature and baryon density, which can be reached in heavy-ion collisions at intermediate energies. The model predicts both first-order liquid-gas phase transition and Bose-Einstein condensation of $\alpha$ particles. We present the profiles of scaled variance, sound velocity and isochoric heat capacity along the isentropic trajectories of $\alpha$ matter. Strong density fluctuations are predicted in the vicinity of the critical point at temperature $T_c\approx 14\text{MeV}$ and density $n_c\approx 0.012{\text{fm}}^{-3}$.

    ↳ nucl-thhep-phPRC(2021)·14 citations
35. 35*

    Uncertainties in the Galactic dark matter distribution: an update

    Maria Benito🇪🇪 · Fabio Iocco🇮🇹 · Alessandro Cuoco🇮🇹

    We present here a quantitative, accurate estimate of the impact of uncertainties of astrophysical nature on the determination of the dark matter distribution within our Galaxy, the Milky Way. Based on an update of a previous analysis, this work is motivated by recent new determinations of astrophysical quantities of relevance -- such as the Galactic parameters (R0,V0) -- from the GRAVITY collaboration and the GAIA satellite, respectively. We find that even with these state-of-the-art determination and a range of uncertainties -- both statistical and systematic -- much narrowed with respect to previous work, the uncertainties on the dark matter distribution and their impact on searches of physics beyond the standard model stays sizable.

    ↳ astro-ph.GAhep-phPhys.Dark Univ.(2021)·83 citations
36. 36*

    Constraining power of asymptotic safety for scalar fields

    Astrid Eichhorn🇩🇰 · Martin Pauly🇩🇪

    We explore the phenomenology of scalar fields coupled to asymptotically safe quantum gravity, in light of their potential significance for dark matter, for the inflaton as well as dynamical dark energy, and in the Higgs sector in and beyond the Standard Model. This work is a step towards delineating the boundaries of the asymptotically safe swampland by exploiting the constraining power of the asymptotic-safety paradigm. Firstly, we strengthen indications that quantum gravitational fluctuations could drive scalar potentials towards flatness, with intriguing potential implications for inflation and dark energy. Secondly, we explore how asymptotic safety could rule out large parts of the parameter space in models for scalar dark matter. Thirdly, we discover hints that at an asymptotically safe fixed point with finite top quark mass, the non-minimal Higgs-curvature coupling could be constrained. Finally, by combining the constraining power of asymptotic safety in particle physics and cosmology, we find hints that Higgs inflation lies in the asymptotically safe swampland. In summary, we strengthen previous indications for the constraining power of asymptotic safety and the resulting large extent of the asymptotically safe swampland.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2021)·78 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.