Mon·Oct 19, 2020Monday·October 19, 2020

1. 01*

   Cosmological bubble friction in local equilibrium

   Shyam Balaji🇦🇺 · Michael Spannowsky🇬🇧 · Carlos Tamarit🇩🇪

   In first-order cosmological phase transitions, the asymptotic velocity of expanding bubbles is of crucial relevance for predicting observables like the spectrum of stochastic gravitational waves, or for establishing the viability of mechanisms explaining fundamental properties of the universe such as the observed baryon asymmetry. In these dynamic phase transitions, it is generally accepted that subluminal bubble expansion requires out-of-equilibrium interactions with the plasma which are captured by friction terms in the equations of motion for the scalar field. This has been disputed in works pointing out subluminal velocities in local equilibrium arising either from hydrodynamic effects in deflagrations or from the entropy change across the bubble wall in general situations. We argue that both effects are related and can be understood from the conservation of the entropy of the degrees of freedom in local equilibrium, leading to subluminal speeds for both deflagrations and detonations. The friction effect arises from the background field dependence of the entropy density in the plasma, and can be accounted for by simply imposing local conservation of stress-energy and including field dependent thermal contributions to the effective potential. We illustrate this with explicit calculations of dynamic and static bubbles for a first-order electroweak transition in a Standard Model extension with additional scalar fields.

   hep-phastro-ph.COhep-thJCAP(2021)·95 citations
2. 02*

   Extracting Signals of Higgs Boson From Background Noise Using Deep Neural Networks

   Muhammad Abbas🇵🇰 · Asifullah Khan🇵🇰 · Aqsa Saeed Qureshi🇵🇰 · Muhammad Waleed Khan🇵🇰

   Higgs boson is a fundamental particle, and the classification of Higgs signals is a well-known problem in high energy physics. The identification of the Higgs signal is a challenging task because its signal has a resemblance to the background signals. This study proposes a Higgs signal classification using a novel combination of random forest, auto encoder and deep auto encoder to build a robust and generalized Higgs boson prediction system to discriminate the Higgs signal from the background noise. The proposed ensemble technique is based on achieving diversity in the decision space, and the results show good discrimination power on the private leaderboard; achieving an area under the Receiver Operating Characteristic curve of 0.9 and an Approximate Median Significance score of 3.429.

   hep-phcs.CVcs.LG6 citations
3. 03*

   Exploring the Origin of CP Violation in the Standard Model

   Chilong Lin🇹🇼

   In this article, we present a very general but not ultimate solution of CPV problem in the standard model. Our study starts from a naturally Hermitian ${\mathbf{M}}^2\equiv M^q\cdot M^{q†}$ rather than the previously assumed Hermitian $M^q$. The only assumption employed here is that the real part and imaginary part of ${\mathbf{M}}^2$ can be, respectively, diagonalized by a common ${\mathbf{U}}^{\mathbf{q}}$ matrix. Such an assumption leads to a ${\mathbf{M}}^2$ pattern which depends on only five parameters and can be diagonalized analytically by a ${\mathbf{U}}^{\mathbf{q}}$ matrix which depends on only two of the parameters. Two of the derived mass eigenvalues are predicted degenerate if one of the parameters $\mathbf{C}({\mathbf{C}}^{\prime })$ in up- (down-) quark sector is zero. As the ${\mathbf{U}}^{\mathbf{q}}$ patterns are obtained, thirty-six $V_{CKM}$ candidates are yielded and only eight of them, classified into two groups, fit empirical data within the order of $O(\lambda )$. One of the groups is further excluded in a numerical test, and the surviving group predicts that the degenerate pair in a quark type are the lightest and the heaviest generations rather than the lighter two generations assumed in previous researches. However, there is still one unsatisfactory prediction in this research, a quadruple equality in which four CKM elements of very different values are predicted to be equal. It indicates the ${\mathbf{M}}^2$ pattern studied here is still oversimplified by that employed assumption and the ultimate solution can only be obtained by diagonalizing the unsimplified ${\mathbf{M}}^2$ matrix containing nine parameters directly. The $V_{CKM}$ presented here is already very close to such an ultimate CPV solution.

   hep-phLHEP(2021)·3 citations
4. 04*

   Constraining resonances by using the electroweak effective theory

   Ignasi Rosell🇪🇸 · Antonio Pich🇪🇸 · Juan José Sanz-Cillero🇪🇸

   In the light of the mass gap between Standard Model (SM) states and possible new particles, effective field theories are a suitable approach. We take on the non-linear realization of the electroweak symmetry breaking: the electroweak effective theory (EWET), also known as Higgs effective field theory (HEFT) or electroweak chiral Lagrangian (EWChL). At higher scales we consider a resonance electroweak Lagrangian, coupling SM fields to resonances. Integrating out these resonances and assuming a well-behaved high-energy behavior, some of the bosonic low-energy constants are determined or constrained in terms of resonance masses. Present experimental bounds on these low-energy constants allow us to push the resonance mass scale to the TeV range, $M_R\ge 2$TeV, in good agreement with previous estimations.

   hep-phPoS(2021)·6 citations
5. 05*

   Self-Similarity, Fractality and Entropy Principle in Collisions of Hadrons and Nuclei at Tevatron, RHIC and LHC

   I. Zborovsky🇨🇿 · M. Tokarev🇷🇺

   $z$-Scaling of inclusive spectra as a manifestation of self-similarity and fractality of hadron interactions is illustrated. The scaling for negative particle production in $Au+Au$ collisions from BES-I program at RHIC is demonstrated. The scaling variable $z$ depends on the momentum fractions of the colliding objects carried by the interacting constituents, and on the momentum fractions of the fragmenting objects in the scattered and recoil directions carried by the inclusive particle and its counterpart, respectively. Structures of the colliding objects and fragmentation processes in final state are expressed by fractal dimensions. Medium produced in the collisions is described by a specific heat. The scaling function $\psi (z)$ reveals energy, angular, multiplicity, and flavor independence. It has a power behavior at high $z$ (high $p_T$). Based on the entropy principle and $z$-scaling, energy loss as a function of the collision energy, centrality and transverse momentum of inclusive particle is estimated. New conservation law including fractal dimensions is found. Quantization of fractal dimensions is discussed.

   hep-phhep-exnucl-exPoS(2021)·3 citations
6. 06*

   Coloured Scalar Mediated Nucleon Decays to Invisible Fermion

   Svjetlana Fajfer🇸🇮 · David Susič🇸🇮

   We investigate nucleon decays to light invisible fermion mediated by the coloured scalar ${\bar{S}}_1=(\bar{3},1,-2/3)$ and compare them with the results coming from the mediation of $S_1=(\bar{3},1,1/3)$. In the case of ${\bar{S}}_1=(\bar{3},1,-2/3)$ up-like quarks couple to the invisible fermion, while in the case of $S_1=(\bar{3},1,1/3)$ the down-like quarks couple to the invisible fermion. For the mass of invisible fermion smaller than the mass $m_p-m_K$, proton (neutron) can decay to $K$ and invisible fermion and the masses of ${\bar{S}}_1$ and $S_1$ are in the region $\sim 10^{15}$ GeV. The decays of nucleons to pions and invisible fermion can occur at the tree-level, but in the case of ${\bar{S}}_1$ they come from dimension-9 operator and are therefore suppressed by several orders of magnitude compared to the decays into kaons. For the invisible fermion mass in the range $(937.8\mathrm{MeV},938.8\mathrm{MeV})$, decay of neutron $n\to \chi \gamma$ induced by ${\bar{S}}_1$ is possible at the loop level, while the proton remains stable. The branching ratio of such decay is $\le 10^{-6}$, which does not explain neutron decay anomaly, but is in agreement with the Borexino experiment bound. We comment on low-energy processes with the nucleon-like mass of $\chi$ in the final state as $\Lambda \to \chi \gamma$ and heavy hadron decays to invisibles.

   hep-phhep-exPRD(2021)·30 citations
7. 07*

   One loop verification of SMEFT Ward Identities

   Tyler Corbett🇩🇰 · Michael Trott🇩🇰

   We verify Standard Model Effective Field Theory Ward identities to one loop order when background field gauge is used to quantize the theory. The results we present lay the foundation of next to leading order automatic generation of results in the SMEFT, in both the perturbative and non-perturbative expansion using the geoSMEFT formalism, and background field gauge.

   hep-phSciPost Phys.(2021)·16 citations
8. 08*

   Bound states in the B-matrix formalism for the three-body scattering

   Sebastian M. Dawid🇺🇸 · Adam P. Szczepaniak🇺🇸

   We consider a model of relativistic three-body scattering with a bound state in the two-body sub-channel. We show that the naïve K-matrix type parametrization, here referred to as the B-matrix, has nonphysical singularities near the physical region. We show how to eliminate such singularities by using dispersion relations and also show how to reproduce unitarity relations by taking into account all relevant open channels.

   ↳ nucl-thhep-phhep-thPRD(2021)·18 citations
9. 09*

   Spinors and Scalars in curved spacetime: neutrino dark energy (DE${}_{\nu }$)

   Ali Rida Khalifeh🇪🇸 · Raul Jimenez🇪🇸

   We study the interaction, in general curved spacetime, between a spinor and a scalar field describing dark energy; the so-called DE${}_{\nu }$ model in curved space. The dominant term is the dimension 5 operator, which results in different energy shifts for the neutrino states: an Aharonov-Bohm-like effect. We study the phenomenology of this term and make observational predictions to detect dark energy interactions in the laboratory due to its effect on neutrino oscillation experiments, which opens up the possibility of designing underground experiments to detect dark energy. This dimension 5 operator beyond the Standard Model interaction is less suppressed than the widely discussed dimension 6 operator, which corresponds to mass varying neutrinos; the dimension 5 operator does not suffer from gravitational instabilities.

   ↳ gr-qcastro-ph.COhep-phhep-thPhys.Dark Univ.(2021)·7 citations
10. 10*

    Yangian Bootstrap for Massive Feynman Integrals

    Florian Loebbert🇩🇪 · Julian Miczajka🇩🇪 · Dennis Müller🇩🇰 · Hagen Münkler🇨🇭

    We extend the study of the recently discovered Yangian symmetry of massive Feynman integrals and its relation to massive momentum space conformal symmetry. After proving the symmetry statements in detail at one and two loop orders, we employ the conformal and Yangian constraints to bootstrap various one-loop examples of massive Feynman integrals. In particular, we explore the interplay between Yangian symmetry and hypergeometric expressions of the considered integrals. Based on these examples we conjecture single series representations for all dual conformal one-loop integrals in D spacetime dimensions with generic massive propagators.

    ↳ hep-thhep-phmath-phmath.MPSciPost Phys.(2021)·37 citations
11. 11*

    Leading Nonlinear Tidal Effects and Scattering Amplitudes

    Zvi Bern🇺🇸 · Julio Parra-Martinez🇺🇸 · Radu Roiban🇺🇸 · Eric Sawyer🇺🇸 · Chia-Hsien Shen🇺🇸

    We present the two-body Hamiltonian and associated eikonal phase, to leading post-Minkowskian order, for infinitely many tidal deformations described by operators with arbitrary powers of the curvature tensor. Scattering amplitudes in momentum and position space provide systematic complementary approaches. For the tidal operators quadratic in curvature, which describe the linear response to an external gravitational field, we work out the leading post-Minkowskian contributions using a basis of operators with arbitrary numbers of derivatives which are in one-to-one correspondence with the worldline multipole operators. Explicit examples are used to show that the same techniques apply to both bodies interacting tidally with a spinning particle, for which we find the leading contributions from quadratic in curvature tidal operators with an arbitrary number of derivatives, and to effective field theory extensions of general relativity. We also note that the leading post-Minkowskian order contributions from higher-dimension operators manifest double-copy relations. Finally, we comment on the structure of higher-order corrections.

    ↳ hep-thgr-qchep-phJHEP(2021)·155 citations
12. 12*

    EFT Asymptotics: the Growth of Operator Degeneracy

    Tom Melia🇯🇵 · Sridip Pal🇺🇸

    We establish formulae for the asymptotic growth (with respect to the scaling dimension) of the number of operators in effective field theory, or equivalently the number of $S$-matrix elements, in arbitrary spacetime dimensions and with generic field content. This we achieve by generalising a theorem due to Meinardus and applying it to Hilbert series -- partition functions for the degeneracy of (subsets of) operators. Although our formulae are asymptotic, numerical experiments reveal remarkable agreement with exact results at very low orders in the EFT expansion, including for complicated phenomenological theories such as the standard model EFT. Our methods also reveal phase transition-like behaviour in Hilbert series. We discuss prospects for tightening the bounds and providing rigorous errors to the growth of operator degeneracy, and of extending the analytic study and utility of Hilbert series to EFT.

    ↳ hep-thhep-phmath-phmath.MPSciPost Phys.(2021)·31 citations
13. 13*

    On the Possibility of Dibaryon Formation near the N*(1440)N threshold -- the Isoscalar Single-Pion Production Revisited

    H. Clement🇩🇪 · T. Skorodko🇩🇪 · E. Doroshkevich🇷🇺

    The isoscalar single-pion production exhibits a broad bump in the energy dependence of the total cross section, which does not correspond to the usual opening of the $N^{\ast }(1440)$ production channel with subsequent pion decay. In arxiv:2102.05575 it was interpreted as a narrow Breit-Wigner structure, which leads in a sequential single-pion production process to a possible explanation of the $d^{\ast }(2380)$ resonance. We demonstrate that such an attempt fails already, when confronted with the data base for isoscalar single-pion production. We investigate whether the observed bump structure rather points to the formation of dibaryon states with $I(J^P)=0(1^{+})$ and $0(1^{-})$ near the $N^{\ast }(1440)N$ threshold. This situation would be similar to the situation at the $\Delta (1232)N$ threshold, where the signature of a number of dibaryonic resonances has been found.

    ↳ nucl-exhep-exhep-phnucl-thPRC(2022)·14 citations
14. 14*

    GUP effects on Hawking temperature in Riemann space-time

    Y. Kenedy Meitei🇮🇳 · T. Ibungochouba Singh🇮🇳 · I. Ablu Meitei🇮🇳

    In this paper, the modified Hawking temperature of a static Riemann space-time is studied using the generalized Klein-Gordon equation and the generalized Dirac equation. Applying the Kerner-Mann quantum tunneling method, the modified Hawking temperature for scalar particle and fermions that crosses the event horizon of the black hole have been derived. We observe that the quantum gravity effect reduces the rise of thermal radiation temperature of the black hole.

    ↳ gr-qchep-phTurk.J.Phys.(2020)·5 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.