Thu·Jul 15, 2021Thursday·July 15, 2021

1. 01*

   On the role of leptonic CPV phases in cLFV observables

   A. Abada🇫🇷 · J. Kriewald🇫🇷 · A. M. Teixeira🇫🇷

   In extensions of the Standard Model by Majorana fermions, the presence of additional CP violating phases has been shown to play a crucial role in lepton number violating processes. In this work we show that (Dirac and Majorana) CP violating phases can also lead to important effects in charged lepton flavour violating (cLFV) transitions and decays, in some cases with a significant impact for the predicted rates of cLFV observables. We conduct a thorough exploration of these effects in several cLFV observables, and discuss the implications for future observation. We emphasise how the presence of leptonic CP violating phases might lead to modified cLFV rates, and to a possible loss of correlation between cLFV observables.

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

   Anomalous measurements: recent results deepen flavour puzzle

   D. Lancierini🇨🇭 · R.D. Moise🇬🇧

   The crown jewel of particle physics, the Standard Model (SM), has withstood numerous experimental trials. However, there are still some observations it cannot explain. Examples such as dark matter and the matter-antimatter imbalance in the Universe come to mind. The SM may be extended, by including additional particles and interactions, so as to explain such phenomena. These new particles and interactions are collectively referred to as "new physics" (NP), and the results covered by this article provide a promising lead for their discovery.

   hep-phhep-ex0 citations
3. 03*

   Search for axion-like particles with electron and positron beams at KEK Linac

   Akimasa Ishikawa🇯🇵 · Yasuhito Sakaki🇯🇵 · Yosuke Takubo🇯🇵

   We propose a fixed-target experiment to search for Axion-like particles (ALPs) coupling to photons, which utilizes electron and positron beams available at KEK Linac. The sensitivity to ALP is evaluated for two shielding setups in conjunction with other beam dump experiments, fixed-target experiments, and $e^{+}{e}^{-}$ collider experiments. This study shows that the two setups can explore the gap between the search region excluded by the beam dump experiments and the $e^{+}{e}^{-}$ collider experiments.

   hep-phhep-exPTEP(2022)·10 citations
4. 04*

   Real-time dynamics of the $O(4)$ scalar theory within the fRG approach

   Yang-yang Tan🇨🇳 · Yong-rui Chen🇨🇳 · Wei-jie Fu🇨🇳

   In this paper, the real-time dynamics of the $O(4)$ scalar theory is studied within the functional renormalization group formulated on the Schwinger-Keldysh closed time path. The flow equations for the effective action and its $n$-point correlation functions are derived in terms of the "classical" and "quantum" fields, and a concise diagrammatic representation is presented. An analytic expression for the flow of the four-point vertex is obtained. Spectral functions with different values of temperature and momentum are obtained. Moreover, we calculate the dynamical critical exponent for the phase transition near the critical temperature in the $O(4)$ scalar theory in $3+1$ dimensions, and the value is found to be $z\simeq 2.023$.

   hep-phhep-thSciPost Phys.(2022)·30 citations
5. 05*

   Vortex Breit-Wheeler Electron-positron pair creation via vortex gamma-photons

   Zhigang Bu🇨🇳 · Liangliang Ji🇨🇳 · Shaohu Lei🇨🇳 · Huayu Hu🇨🇳 · Xiaomei Zhang🇨🇳 · Baifei Shen🇨🇳

   Particles in quantum vortex states (QVS) carrying definite orbital angular momenta (OAM) brings new perspectives in various fundamental interaction processes. When unique properties arise in the QVS, understanding how OAM manifest itself between initial particles and the outcome in vortex particle collisions becomes essential. This is made possible by applying the complete vortex description for all involved particles such that angular momenta (AM) are represented by explicit quantum numbers and their connections are naturally retrieved. We demonstrate the full-vortex quantum-electrodynamics (QED) results for the Breit-Wheeler pair creation process and derive the AM-dependent selection rule. The numerically resolved cross-sections show anti-symmetric spin polarization and most importantly, the first OAM spectra in vortex collision processes. The latter reveals efficient conversion of OAM to created pairs, leading to featured hollow and ring-shaped structure in the density distribution. These results demonstrate a clear picture in understanding the OAM physics in the scattering processes of high energy particles.

   hep-phhep-thPRResearch(2021)·16 citations
6. 06*

   Radiation Production by Axion in Space between Two Flat Conductors

   Aiichi Iwazaki🇯🇵

   We have shown a new production mechanism of radiations produced by dark matter axion $a(t)$ under strong magnetic field $B$. The axion generates oscillating electric current in the surface of conductor. The current is extremely enhanced such as $J_c=(m_a{\delta }_e{)}^{-2}{J}_a$ compared with vacuum current $J_a\equiv g_{a\gamma \gamma }{\partial }_{t}a(t)B$; ${\delta }_e$ is skin depth and axion mass $m_a$. We have shown that sufficiently strong radiation is emitted by cylindrical super ( normal ) conductor to be easily detected. Then, we naively expect that such strong radiation also arises in resonant cavity experiment. But we show that the expectation is wrong. The radiation generated in the cavity is just the one given in the standard estimation, even if we consider the enhanced current in the conductor of the cavity. This is because the radiation in the cavity is standing wave, while the radiation emitted from the cylindrical conductor is outgoing wave. For simplicity we consider radiation arising in the space between two parallel flat conductors.

   hep-ph0 citations
7. 07*

   NLO EW and QCD corrections to polarized ZZ production in the four-charged-lepton channel at the LHC

   Ansgar Denner🇩🇪 · Giovanni Pelliccioli🇩🇪

   Measuring the polarization of electroweak bosons at the LHC allows for important tests of the electroweak-symmetry-breaking mechanism that is realized in nature. Therefore, precise Standard Model predictions are needed for the production of polarized bosons in the presence of realistic kinematic selections. We formulate a method for the calculation of polarized cross-sections at NLO that relies on the pole approximation and the separation of polarized matrix elements at the amplitude level. In this framework, we compute NLO-accurate cross-sections for the production of two polarized Z bosons at the LHC, including for the first time NLO EW corrections and combining them with NLO QCD corrections and contributions from the gluon-induced process.

   hep-phhep-exJHEP(2021)·62 citations
8. 08*

   A factorisation-aware Matrix element emulator

   Daniel Maître🇬🇧 · Henry Truong

   In this article we present a neural network based model to emulate matrix elements. This model improves on existing methods by taking advantage of the known factorisation properties of matrix elements. In so doing we can control the behaviour of simulated matrix elements when extrapolating into more singular regions than the ones used for training the neural network. We apply our model to the case of leading-order jet production in $e^{+}{e}^{-}$ collisions with up to five jets. Our results show that this model can reproduce the matrix elements with errors below the one-percent level on the phase-space covered during fitting and testing, and a robust extrapolation to the parts of the phase-space where the matrix elements are more singular than seen at the fitting stage.

   hep-phJHEP(2021)·71 citations
9. 09*

   No-scale gauge non-singlet inflation inducing TeV scale inverse seesaw mechanism

   Ahmad Moursy🇪🇬

   We develop a model of sneutrino inflation that is charged under $U(1{)}_{B-L}$ gauge symmetry in no-scale supergravity framework. The model provides an interesting modification of tribrid inflation. We impose $U(1{)}_R$ symmetry on the renormalizable level while allow Planck suppressed non-renormalizable operators that break R-symmetry. This plays a crucial role in realizing a Starobinsly-like inflation scenario from one hand. On the other hand it plays essential role, as well as SUSY breaking effects, in deriving the neutrino masses from TeV inverse seesaw mechanism. Thus we provide an interpretation for the extremely small value of the ${\mu }_S$ mass parameter required for inverse seesaw mechanism. We discuss the reheating scenario and the possible constraints on the parameter space in connection to neutrino masses.

   hep-phJHEP(2021)·6 citations
10. 10*

    Progress and Opportunities in Backward angle (u-channel) Physics

    C. Ayerbe Gayoso🇺🇸 · Ł. Bibrzycki🇵🇱 · S. Diehl🇺🇸 · S. Heppelmann🇺🇸 · D.W. Higinbotham🇺🇸 · G.M. Huber🇨🇦 · S.J.D. Kay🇨🇦 · S.R. Klein🇺🇸 · J.M. Laget🇺🇸 · W.B. Li🇺🇸 · V. Mathieu🇪🇸 · K. Park🇺🇸 and 8 other authors

    Backward angle (u-channel) scattering provides complementary information for studies of hadron spectroscopy and structure, but has been less comprehensively studied than the corresponding forward angle case. As a result, the physics of u-channel scattering poses a range of new experimental and theoretical opportunities and questions. We summarize recent progress in measuring and understanding high energy reactions with baryon charge exchange in the u-channel, as discussed in the first backward angle (u-channel) Physics Workshop. In particular, we discuss backward angle measurements and their theoretical description via both hadronic models and the collinear factorization approach, and discuss planned future measurements of u-channel physics. Finally, we propose outstanding questions and challenges for u-channel physics.

    hep-phnucl-exnucl-thEPJA(2021)·22 citations
11. 11*

    MiNNLO${}_{\mathrm{PS}}$: a new method to match NNLO QCD with parton showers

    Emanuele Re🇫🇷

    I describe MiNNLO${}_{\mathrm{PS}}$, a novel method to match NNLO QCD computations with Parton Showers, and present a selection of results for color-singlet production at the LHC.

    hep-ph1 citation
12. 12*

    Probing the interaction of semi-hard quarks and gluons with the underlying event in light- and heavy-flavor triggered proton-proton collisions

    Róbert Vértesi🇭🇺 · Gyula Bencédi🇭🇺 · Anett Misák🇭🇺 · Antonio Ortiz🇲🇽

    We study underlying-event observables in inelastic proton-proton (pp) collisions at a centre-of-mass energy of $\sqrt{s}=13$ TeV with identified light and heavy-flavor triggers using the PYTHIA 8 event generator. The study is performed as a function of the transverse momentum of the leading particle ($p_{\mathrm{T}}^{\mathrm{trigger}}$). While at high $p_{\mathrm{T}}^{\mathrm{trigger}}$ ($>10$ GeV/$c$) the underlying-event activity is independent of the leading particle species, at intermediate $p_{\mathrm{T}}^{\mathrm{trigger}}$ ($2<p_{\mathrm{T}}^{\mathrm{trigger}}<8$ GeV/$c$) it is larger in pion-triggered events than in events triggered with B mesons. Moreover, the underlying event in pion-triggered events, the majority of which are initiated by gluons, shows a stronger effect of color reconnection than events triggered with B-hadrons, that are mostly initiated by quark jets. The effect is observed at both hadronic and partonic level. Given that color reconnection affects the interaction among final partons before the hadronization, and that in the string model quarks (gluons) are connected to one (two) string piece(s), we conclude that the observed effect can be attributed to differences in the interactions of gluon and quark jets with the underlying event.

    hep-phEPJA(2021)·3 citations
13. 13*

    Where do we stand with a 3-D picture of the proton?

    Alessandro Bacchetta🇮🇹

    We are on the way to obtaining multi-dimensional "pictures" of the proton. The field is bursting with activities, both from the theoretical and experimental side. A brief selection of important achievements of the last years and open challenges for the future is presented. They are already well documented in the various reviews of this Special Issue, but they are gathered here in a more condensed way for convenience, together with some additional remarks. The choice of the items included in this short overview is far from being complete and represents the view of the author.

    hep-phEPJA(2016)·49 citations
14. 14*

    Logarithmic corrections to the QCD component of same-sign W-pair production for VBS studies

    Jeppe R. Andersen🇬🇧 · Bertrand Ducloué🇬🇧 · Conor Elrick🇬🇧 · Andreas Maier🇩🇪 · Graeme Nail🇬🇧 · Jennifer M. Smillie🇬🇧

    We present the results of the first calculation of the logarithmic corrections to the QCD contribution to same-sign $W$-pair production, $pp\to e^{\pm }{\nu }_e{\mu }^{\pm }{\nu }_{\mu }jj$, for same-sign charged leptons. This includes all leading logarithmic contributions which scale as ${\alpha }_W^4{\alpha }_s^{2+k}{\log }^k(\hat{s}/p_{\perp }^2)$. This process is important for the study of electroweak couplings and hence the QCD contributions are usually suppressed through a choice of Vector Boson Scattering (VBS) cuts. These select regions of phase space where logarithms in $\hat{s}/p_{\perp }^2$ are enhanced. While the logarithmic corrections lead to a small change for the cross sections, several distributions relevant for experimental studies are affected more significantly.

    hep-phPRD(2021)·6 citations
15. 15*

    Probing Quark-Lepton Unification with Leptoquark and Higgs Decays

    Pavel Fileviez Perez🇺🇸 · Elliot Golias🇺🇸 · Alexis D. Plascencia🇺🇸

    We point out unique relations between the decay widths for leptoquarks and Higgs bosons that can be used to test the unification of quarks and leptons at the TeV scale. We discuss the main predictions of the minimal theory for quark-lepton unification and show how the different decays for leptoquarks and Higgses are related by the symmetry of the theory.

    hep-phhep-exPRD(2022)·7 citations
16. 16*

    Nucleon-nucleon potentials from Delta-full chiral effective-field-theory and implications

    Y. Nosyk🇺🇸 · D. R. Entem🇪🇸 · R. Machleidt🇺🇸

    We closely investigate NN potentials based upon the Delta-full version of chiral effective field theory. We find that recently constructed NN potentials of this kind, which (when applied together with three-nucleon forces) were presented as predicting accurate binding energies and radii for a range of nuclei from A=16 to A=132 and providing accurate equations of state for nuclear matter, yield a chi^2/datum of 60 for the reproduction of the pp data below 100 MeV laboratory energy. This chi^2 is more than three times what the Hamada-Johnston potential of the year of 1962 achieved already some 60 years ago. We perceive this historical fact as concerning in view of the current emphasis on precision. We are able to trace the very large chi^2 as well as the apparent success of the potentials in nuclear structure to unrealistic predictions for P-wave states, in which the Delta-full NNLO potentials are off by up to 40 times the NNLO truncation errors. In fact, we show that, the worse the description of the P-wave states, the better the predictions in nuclear structure. Thus, these potentials cannot be seen as the solution to the outstanding problems in current miscroscopic nuclear structure physics.

    ↳ nucl-thastro-ph.SRhep-phnucl-exPRC(2021)·31 citations
17. 17*

    Infrared and Holographic Aspects of the $S$-Matrix in Gauge Theory and Gravity

    Nikhil Kalyanapuram🇺🇸

    Soft theorems in gauge theory and gravity encode the universal properties of scattering amplitudes as the zero frequency limit of one or more external states is approached. When the participating particles are treated in the massless limit, the soft theorems are known to depend only on the directions of the states on null infinity. Leveraging this fact, we develop dual two-dimensional descriptions of soft theorems, recasting them as Ward identities of such dual models on the celestial sphere. This is done by first postulating putative holographic representations of the hard scattering amplitudes and dressing the asymptotic operators with appropriate two-dimensional analogues of the Wilson line. The soft theorems are then recovered by inserting currents that generate the Ward identities of the dual models. In addition to providing naturally holographic representations of the soft theorems, we see that it becomes possible to develop presentations of the asymptotic symmetries associated to these theorems entirely in terms of the dual two-dimensional fields. In the course of carrying out this analysis for soft theorems at leading order and beyond, we find that the two-dimensional dual description of soft theorems may be directly inferred by drawing analogies with the existing framework of asymptotic symmetry charges. We find that the soft charges generating the asymptotic symmetries can be brought into correspondence with dual two-dimensional currents, while the two-dimensional Wilson loops can be related to the hard parts of the conserved charges. Consequently, we rewrite the triality of asymptotic symmetries, soft theorems and conserved charges directly in the language of a class of two-dimensional theories.

    ↳ hep-thhep-ph13 citations
18. 18*

    First Measurement of the Absolute Branching Fraction of $\Lambda \to p{\mu }^{-}{\bar{\nu }}_{\mu }$

    M. Ablikim (1) · M. N. Achasov (10, b) · P. Adlarson (67) · S. Ahmed (15) · M. Albrecht (4) · R. Aliberti (28) · A. Amoroso (66A,66C) · M. R. An (32) · Q. An (63,49) · X. H. Bai (57) · Y. Bai (48) · O. Bakina (29) and 506 other authors

    The absolute branching fraction of $\Lambda \to p{\mu }^{-}{\bar{\nu }}_{\mu }$ is reported for the first time based on an $e^{+}{e}^{-}$ annihilation sample of ten billion $J/\psi$ events collected with the BESIII detector at $\sqrt{s}=3.097$ GeV. The branching fraction is determined to be $\mathcal{B}(\Lambda \to p{\mu }^{-}{\bar{\nu }}_{\mu })=[1.48\pm 0.21(\mathrm{stat})\pm 0.08(\mathrm{syst})]\times 10^{-4}$, which is a significant improvement in precision over the previous indirect measurements. Combining this result with the world average of $\mathcal{B}(\Lambda \to p{e}^{-}{\bar{\nu }}_e)$, we obtain the ratio, $\frac{\Gamma (\Lambda \to p{\mu }^{-}{\bar{\nu }}_{\mu })}{\Gamma (\Lambda \to p{e}^{-}{\bar{\nu }}_e)}$, to be $0.178\pm 0.028$, which agrees with the standard model prediction assuming lepton flavor universality. The asymmetry of the branching fractions of $\Lambda \to p{\mu }^{-}{\bar{\nu }}_{\mu }$ and $\bar{\Lambda }\to \bar{p}{\mu }^{+}{\nu }_{\mu }$ is also determined, and no evidence for $CP$ violation is found.

    ↳ hep-exhep-phPRL(2021)·28 citations
19. 19*

    Radiation from a dipole perpendicular to the interface between two planar semi-infinite magnetoelectric media

    O. J. Franca🇩🇪 · Luis F. Urrutia🇲🇽

    We consider two semi-infinite magnetoelectric media with constant dielectric permittivity separated by a planar interface, whose electromagnetic response is described by non-dynamical axion electrodynamics and investigate the radiation of a point-like electric dipole located perpendicularly to the interface. We start from the exact Green's function for the electromagnetic potential, whose far-field approximation is obtained using a modified steepest descent approximation. This procedure yields the standard spherical waves as well as axially symmetric cylindrical superficial waves, which nevertheless are restricted to a region very close to the interface. We compute the angular distribution of the radiation and the total radiated power finding different interference patterns, depending on the relative position dipole-observer, and polarization mixing effects which are all absent in the standard dipole radiation. They are a manifestation of the magnetoelectric effect induced by axion electrodynamics. We illustrate our findings with some numerical estimations employing realistic media as well as some hypothetical choices in order to illuminate the effects of the magnetoelectric coupling which is usually very small.

    ↳ cond-mat.othercond-mat.mes-hallhep-phhep-th+1Rev.Mex.Fis.(2022)·10 citations
20. 20*

    Combined analyses of the antiproton production from cosmic-ray interactions and its possible dark matter origin

    Pedro De La Torre Luque🇸🇪

    Recent cosmic-ray (CR) studies have claimed the possibility of an excess on the antiproton flux over the predicted models at around $10$ GeV, which can be the signature of dark matter annihilating into hadronic final states that subsequently form antiprotons. However, this excess is subject to many uncertainties related to the evaluation of the antiproton spectrum produced from spallation interactions of CRs. In this work, we implement a combined Markov-Chain Monte Carlo analysis of the secondary ratios of B, Be and Li and the antiproton-to-proton ratio ($\bar{p}/p$), while also including nuisance parameters to consider the uncertainties related to the spallation cross sections. This study allows us to constrain the Galactic halo height and the rest of propagation parameters, evaluate the impact of cross sections uncertainties in the determination of the antiproton spectrum and test the origin of the excess of antiprotons. In this way, we provide a set of propagation parameters and scale factors for renormalizing the cross sections parametrizations that allow us to reproduce all the ratios of B, Be, Li and $\bar{p}$ simultaneously. We show that the energy dependence of the $\bar{p}/p$ ratio is compatible with a pure secondary origin. We find that the energy dependence of the evaluated $\bar{p}/p$ spectrum matches the AMS-02 data at energies above $\sim 3$GeV, although there is still a nearly constant $\sim 10\%$ excess of $\bar{p}$ over our prediction. We discuss that this discrepancy is more likely explained from a $\sim 10\%$ scaling in the cross sections of antiproton production, rather than a component of dark matter leading to antiprotons. In particular, we find that the best-fit WIMP mass ($\sim 300$ GeV) needed to explain the discrepancy lies above the constraints from most indirect searches of dark matter and the resultant fit is poorer than with a cross sections scaling.

    ↳ astro-ph.HEhep-phJCAP(2021)·36 citations
21. 21*

    Asymptotic Safety: Swampland or Wonderland?

    Ivano Basile🇧🇪 · Alessia Platania🇨🇦

    We investigate the consequences of combining swampland conjectures with the requirement of asymptotic safety. To this end, we explore the infrared regime of asymptotically safe gravity in the quadratic one-loop approximation, and we identify the hypersurface spanned by the endpoints of asymptotically safe renormalization group trajectories. These comprise the allowed values of higher-derivative couplings as well as standard logarithmic form factors. We determine the intersection of this hypersurface with the regions of parameter space allowed by the weak-gravity conjecture, the swampland de Sitter conjecture, and the trans-Planckian censorship conjecture. The latter two depend on some order-one constants, for generic values of which we show that the overlap region is a proper subspace of the asymptotically safe hypersurface. Moreover, the latter lies inside the region allowed by the weak gravity conjecture assuming electromagnetic duality. Our results suggest a non-trivial interplay between the consistency conditions stemming from ultraviolet completeness of the RG flow, black hole physics, and cosmology.

    ↳ hep-thgr-qchep-phUniverse(2021)·48 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.