Wed·Apr 7, 2021Wednesday·April 7, 2021

1. 01*

   Lepton-flavour non-universality of $\bar{B}\to D^{\ast }\ell \bar{\nu }$ angular distributions in and beyond the Standard Model

   Christoph Bobeth🇩🇪 · Marzia Bordone🇮🇹 · Nico Gubernari🇩🇪 · Martin Jung🇮🇹 · Danny van Dyk🇩🇪

   We analyze in detail the angular distributions in $\bar{B}\to D^{\ast }\ell \bar{\nu }$ decays, with a focus on lepton-flavour non-universality. We investigate the minimal number of angular observables that fully describes current and upcoming datasets, and explore their sensitivity to physics beyond the Standard Model (BSM) in the most general weak effective theory. We apply our findings to the current datasets, extract the non-redundant set of angular observables from the data, and compare to precise SM predictions that include lepton-flavour universality violating mass effects. Our analysis shows that the current presentation of the experimental data is not ideal and prohibits the extraction of the full set of relevant BSM parameters, since the number of independent angular observables that can be inferred from data is limited to only four. We uncover a $\sim 4\sigma$ tension between data and predictions that is hidden in the redundant presentation of the Belle 2018 data on $\bar{B}\to D^{\ast }\ell \bar{\nu }$ decays. This tension specifically involves observables that probe $e-\mu$ lepton-flavour universality. However, we find inconsistencies in these data, which renders results based on it suspicious. Nevertheless, we discuss which generic BSM scenarios could explain the tension, in the case that the inconsistencies do not affect the data materially. Our findings highlight that $e-\mu$ non-universality in the SM, introduced by the finite muon mass, is already significant in a subset of angular observables with respect to the experimental precision.

   hep-phhep-exEPJC(2021)·85 citations
2. 02*

   Decay properties of Roper resonance in the holographic QCD

   Daisuke Fujii🇯🇵 · Atsushi Hosaka🇯🇵

   We investigate the one pion decay of the Roper resonance $N^{\ast }(1440)$$\to$$N$$\pi$ in the Sakai-Sugimoto model of the holographic QCD. The nucleon and Roper resonance emerge as ground and first excited states of the collective radial motion of the instanton in the four dimensional space with one extra dimension. It is found that the ratio of the $\pi$$N{N}^{\ast }$ and $\pi$$NN$ couplings, and hence the ratio of $g_A^{N{N}^{\ast }}$ and $g_A^{NN}$, is well reproduced in comparison with the experimental data. The mechanism of this result is due to the collective nature of excitations, which is very different from that of the single particle nature of the constituent quark model. Our results are obtained in the large-$N_c$ and large $\lambda$ ('t~Hooft coupling) limit which are useful to test how baryon resonances share what are expected in these limits.

   hep-phPRD(2021)·12 citations
3. 03*

   Subcritical hybrid inflation in a generalized superconformal model

   Yoshihiro Gunji🇯🇵 · Koji Ishiwata🇯🇵

   We study a generalized superconformal model that gives rise to a subcritical regime of $D$-term hybrid inflation. Exhibiting the model both in a Jordan frame and in the Einstein frame, the effective potential of the subcritical regime is derived in the Einstein frame. It turns out the inflaton-waterfall field dynamics leads to various types of inflaton potential. Consequently the tensor-to-scalar ratio is found to range from $10^{-4}$ ($10^{-3}$) to $0.1$ for getting 60 (50) $e$-folds before the end of inflation.

   hep-phastro-ph.COhep-thPRD(2021)·2 citations
4. 04*

   Jet Transport Coefficient at the Large Hadron Collider Energies in a Color String Percolation Approach

   Aditya Nath Mishra🇭🇺 · Dushmanta Sahu🇮🇳 · Raghunath Sahoo🇮🇳

   Within the color string percolation model (CSPM), jet transport coefficient, $\hat{q}$, is calculated for various multiplicity classes in proton-proton and centrality classes in nucleus-nucleus collisions at the Large Hadron Collider energies for a better understanding of the matter formed in ultra-relativistic collisions. $\hat{q}$ is studied as a function of final state charged particle multiplicity (pseudorapiditydensity at midrapidity), initial state percolation temperature and energy density. The CSPM results are then compared with different theoretical calculations from the JET Collaboration those incorporate particle energy loss in the medium.

   hep-phhep-exhep-thnucl-ex+1Physics(2022)·11 citations
5. 05*

   Exclusive heavy vector meson production at next-to-leading order in the dipole picture

   Heikki Mäntysaari🇫🇮 · Jani Penttala🇫🇮

   We calculate exclusive production of a longitudinally polarized heavy vector meson at next-to-leading order in the dipole picture. The large quark mass allows us to separately include both the first QCD correction proportional to the coupling constant ${\alpha }_s$, and the first relativistic correction suppressed by the quark velocity $v^2$. Both of these corrections are found to be numerically important in $\mathrm{J}/\psi$ production. The results obtained are directly suitable for phenomenological calculations. We also demonstrate how vector meson production provides complementary information to structure function analyses when one extracts the initial condition for the energy evolution of the proton small-$x$ structure.

   hep-phhep-exPLB(2021)·88 citations
6. 06*

   FIMP Dark Matter from Leptogenesis in Fast Expanding Universe

   Zhi-Fang Chang🇨🇳 · Zhao-Xuan Chen🇨🇳 · Jia-Shu Xu🇨🇳 · Zhi-Long Han🇨🇳

   Within the framework of canonical type-I seesaw, a feebly interacting massive particle (FIMP) $\chi$ is introduced as a dark matter candidate. The leptogenesis mechanism and dark matter relic density share a common origin via decays of Majorana neutrinos $N$. Provided an additional species $\phi$ whose energy density red-shifts as ${\rho }_{\phi }\propto a^{-(4+n)}$, the Hubble expansion rate is larger than the standard scenario, i.e., the Universe expands faster. The consequences of such a fast expanding Universe on leptogenesis as well as FIMP dark matter are investigated in detail. We demonstrate a significant impact on the final baryon asymmetry and dark matter abundance due to the existence of $\phi$ for the strong washout scenario. While for the weak washout scenario, the effects of FEU are relatively small. We introduce scale factors $F_L$ and $F_{\chi }$ to describe the corresponding effects of FEU. A semi-analytical approach to derive the efficiency factors ${\eta }_L$ and ${\eta }_{\chi }$ in FEU is also discussed. The viable parameter space for success thermal leptogenesis and correct FIMP DM relic density is obtained for standard cosmology and FEU. Our results show that it is possible to distinguish different cosmology scenarios for strong washout cases.

   hep-phJCAP(2021)·20 citations
7. 07*

   ${}^3{S}_1-{}^3{D}_1$ coupled channel ${\Lambda }_{c}N$ interactions: chiral effective field theory vs. lattice QCD

   Jing Song🇨🇳 · Yang Xiao🇨🇳 · Zhi-Wei Liu🇨🇳 · Kai-Wen Li🇨🇳 · Li-Sheng Geng🇨🇳

   We study the lattice QCD ${\Lambda }_{c}N$ phase shifts for the ${}^3{S}_1-{}^3{D}_1$ coupled channel using both the leading order covariant chiral effective theory and the next-to-leading order non-relativistic chiral effective field theory. We show that although it is possible to describe simultaneously the ${}^3{S}_1$ and ${}^3{D}_1$ phase shifts and the inelasticity ${\eta }_1$, the fitted energy range is pretty small, only up to $E_{c.m.}=5$ MeV. This raises concerns regarding the consistency between leading/next-to-leading order chiral effective field theory and the lattice QCD simulations.

   hep-phhep-latCommun.Theor.Phys.(2023)·7 citations
8. 08*

   Precision studies for Drell-Yan processes at NNLO

   S. Alekhin🇩🇪 · A. Kardos🇭🇺 · S. Moch🇩🇪 · Z. Trócsányi🇭🇺

   We present a detailed comparison of the fixed-order predictions computed by four publicly available computer codes for Drell-Yan processes at the LHC and Tevatron colliders. We point out that while there is agreement among the predictions at the next-to-leading order accuracy, the predictions at the next-to-next-to-leading order (NNLO) differ, whose extent depends on the observable. The sizes of the differences in general are at least similar, sometimes larger than the sizes of the NNLO corrections themselves. We demonstrate that the neglected power corrections by the codes that use global slicing methods for the regularization of double real emissions can be the source of the differences. Depending on the fiducial cuts, those power corrections become linear, hence enhanced as compared to quadratic ones that are considered standard.

   hep-phEPJC(2021)·41 citations
9. 09*

   Photophilic hadronic axion from heavy magnetic monopoles

   Anton V. Sokolov🇩🇪 · Andreas Ringwald🇩🇪

   We propose a model for the QCD axion which is realized through a coupling of the Peccei-Quinn scalar field to magnetically charged fermions at high energies. We show that the axion of this model solves the strong CP problem and then integrate out heavy magnetic monopoles using the Schwinger proper time method. We find that the model discussed yields axion couplings to the Standard Model which are drastically different from the ones calculated within the KSVZ/DFSZ-type models, so that large part of the corresponding parameter space can be probed by various projected experiments. Moreover, the axion we introduce is consistent with the astrophysical hints suggested both by anomalous TeV-transparency of the Universe and by excessive cooling of horizontal branch stars in globular clusters. We argue that the leading term for the cosmic axion abundance is not changed compared to the conventional pre-inflationary QCD axion case for axion decay constant $f_a>10^{12}\text{GeV}$.

   hep-phhep-exhep-thJHEP(2021)·48 citations
10. 10*

    Radiative corrections in the Yukawa model within the null-plane causal perturbation theory framework

    O. A. Acevedo🇧🇷 · B. M. Pimentel🇧🇷

    Practical calculations in light-front dynamics are, as a general rule, complicated, since there is no consensus about how to treat the poles which come from the instantaneous parts of Feynman's propagators of the fields. An alternative to solve this difficulty is null-plane causal perturbation theory, a recent developed framework which prevents the appearance of the mentioned poles by avoiding the usage of Feynman's propagators in "loop distributions", requiring no regularization of the amplitudes. In this study, we treat the radiative corrections in the neutral Yukawa's model in that framework. Particularly, we explicitly calculate the boson and fermion self-energies and show that the results obtained with this approach are equivalent to that of the instant dynamics.

    hep-phhep-thPRD(2021)·5 citations
11. 11*

    Empirical determination of the energy loss of heavy quarks in nuclear collisions at RHIC and LHC energies

    Somnath De🇮🇳 · Sudipan De🇮🇳 · Prashant Shukla🇮🇳

    Heavy quarks produced in the heavy ion collisions loose energy while propagting in the hot partonic matter which finally fragment to heavy ($D$ or $B$) mesons. The energy loss suffered by the heavy quarks is imprinted in the nuclear modification factor as a function of transverse momenta ($p_T$) of these heavy mesons. An alternate measure of in-medium energy loss comes through the effective shift in transverse momentum spectra of hadrons recorded in nucleus-nucleus collisions when it is compared to the same in proton-proton collisions. We start by parametrizing invariant momentum yields of heavy mesons in p+p collisions. The fit function from p+p collisions and measured nuclear modification factor in heavy ion collisions are then utilised to obtain the shift in the transeverse mass $\Delta m_T$ of heavy mesons produced at the RHIC and LHC experiments.The energy loss $\Delta m_T$ so obtained is found to scale with the transverse mass ($m_T$) of heavy mesons through a power law at different energies and centralities of collisions. We have also calculated using theoretical formalism, the total energy loss suffered by a charm quark in quark-gluon plasma produced in Pb~+~Pb collisions at the LHC energies. The evolution of the plasma is described by (2+1) dimensional longitudinal boost-invariant ideal hydrodynamics. It is found that the total energy loss of charm quarks scales with the transverse mass of charm quarks through a similar power law which supports our empirical analysis of energy loss.

    hep-phhep-exnucl-exnucl-thJ.Subatomic Part.Cosmol.(2025)·0 citations
12. 12*

    Spontaneous CP Violation and Horizontal Symmetry in the MSSM: Toward Lepton Flavor Naturalness

    Daniel Aloni🇺🇸 · Pouya Asadi🇺🇸 · Yuichiro Nakai🇨🇳 · Matthew Reece🇺🇸 · Motoo Suzuki🇨🇳

    We study the contributions of supersymmetric models with a $U(1)$ horizontal symmetry and only spontaneous CP breaking to various lepton flavor observables, such as $\mu \to e\gamma$ and the electron electric dipole moment. We show that both a horizontal symmetry and a lack of explicit CP violation can alleviate the existing bounds from such observables. The undetermined $\mathcal{O}(1)$ coefficients in such mass matrix models muddle the interpretation of the bounds from various flavor observables. To overcome this, we define a new fine-tuning measure for different observables in such setups. This allows us to study how naturally the observed IR flavor observables can emerge from a given mass matrix model. We use our flavor-naturalness measure in study of our supersymmetric models and quantify the degree of fine tuning required by the bounds from various lepton flavor observables at each mass scale of sleptons, neutralinos, and charginos.

    hep-phJHEP(2021)·21 citations
13. 13*

    Detecting Bosonic Dark Matter with Neutron Stars

    Tarak Nath Maity🇮🇳 · Farinaldo S Queiroz🇧🇷

    What if the dark matter-nucleon scattering cross section is too small to be detected by direct detection experiments? It is well known in the literature that some interactions lead to dark matter-nucleon scattering cross sections that can be velocity and momentum suppressed. We show that in the case of bosonic dark matter, neutron star spectroscopy offers a possible detection. Firstly, we discuss the case of scalar dark matter with scalar, pseudoscalar, and vector mediators. Later, we do this exercise for vector dark matter. We show that, depending on the nature of dark matter and the interaction involved, neutron stars can improve the sensitivity on the dark matter-nucleon scattering cross section by orders of magnitude, representing a major step forward in the dark matter siege.

    hep-phPRD(2021)·50 citations
14. 14*

    Parton distributions in the SMEFT from high-energy Drell-Yan tails

    Admir Greljo🇨🇭 · Shayan Iranipour🇬🇧 · Zahari Kassabov🇬🇧 · Maeve Madigan🇬🇧 · James Moore🇬🇧 · Juan Rojo🇳🇱 · Maria Ubiali🇬🇧 · Cameron Voisey🇬🇧

    The high-energy tails of charged- and neutral-current Drell-Yan processes provide important constraints on the light quark and anti-quark parton distribution functions (PDFs) in the large-x region. At the same time, short-distance new physics effects such as those encoded by the Standard Model Effective Field Theory (SMEFT) would induce smooth distortions to the same high-energy Drell-Yan tails. In this work, we assess for the first time the interplay between PDFs and EFT effects for high-mass Drell-Yan processes at the LHC and quantify the impact that the consistent joint determination of PDFs and Wilson coefficients has on the bounds derived for the latter. We consider two well-motivated new physics scenarios: $1)$ electroweak oblique corrections $(\hat{W},\hat{Y})$ and $2)$ four-fermion interactions potentially related to the LHCb anomalies in $R(K^{(\ast )})$. We account for available Drell-Yan data, both from unfolded cross sections and from searches, and carry out dedicated projections for the High-Luminosity LHC. Our main finding is that, while the interplay between PDFs and EFT effects remains moderate for the current dataset, it will become a significant challenge for EFT analyses at the HL-LHC.

    hep-phJHEP(2021)·112 citations
15. 15*

    Fermion masses and mixings, dark matter, leptogenesis and $g-2$ muon anomaly in an extended 2HDM with inverse seesaw

    A. E. Cárcamo Hernández🇨🇱 · Catalina Espinoza🇲🇽 · Juan Carlos Gómez-Izquierdo🇲🇽 · Myriam Mondragón🇲🇽

    We propose a predictive $Q_4$ flavored 2HDM model, where the scalar sector is enlarged by the inclusion of several gauge singlet scalars and the fermion sector by the inclusion of right handed Majorana neutrinos. In our model, the $Q_4$ family symmetry is supplemented by several auxiliary cyclic symmetries, whose spontaneous breaking produces the observed pattern of SM charged fermion masses and quark mixing angles. The light active neutrino masses are generated from an inverse seesaw mechanism at one loop level thanks to a remnant preserved $Z_2$ symmetry. Our model succesfully reproduces the measured dark matter relic abundance and is consistent with direct detection constraints for masses of the DM candidate around $\sim$ 6.3 TeV. Furthermore, our model is also consistent with the lepton and baryon asymmetries of the Universe as well as with the muon anomalous magnetic moment

    hep-phEur.Phys.J.Plus(2022)·38 citations
16. 16*

    Challenges in Solving Chiral Hydrodynamics

    Enrico Speranza🇺🇸 · Fabio S. Bemfica🇧🇷 · Marcelo M. Disconzi🇺🇸 · Jorge Noronha🇺🇸

    We prove that ideal chiral hydrodynamics, as derived from chiral kinetic theory, is acausal and its initial-value problem is ill-posed both in the linearized case around a local equilibrium solution and also in the full nonlinear regime. Therefore, such theory cannot be used to determine how the chiral anomaly affects the hydrodynamic evolution. We show that these fundamental issues can be fixed by using different definitions (frames) for the hydrodynamic fields. This leads to a causal theory of ideal chiral hydrodynamics where the vorticity strength is constrained by the coefficient that encodes the anomaly.

    ↳ hep-thhep-phnucl-thPRD(2023)·40 citations
17. 17*

    The Golden Ratio and Hydrodynamics

    Boris Khesin · Hanchun Wang🇯🇵

    There are useful and useless golden ratios. The useful one helps in traffic. The useless and rather mysterious one arises in hydrodynamics of point vortices, which we discuss in detail.

    ↳ math.DShep-phmath-phmath.MP0 citations
18. 18*

    The pion and kaon $⟨x^3⟩$ from lattice QCD and PDF reconstruction from Mellin moments

    Constantia Alexandrou🇨🇾 · Simone Bacchio🇨🇾 · Ian Cloët🇺🇸 · Martha Constantinou🇺🇸 · Kyriakos Hadjiyiannakou🇨🇾 · Giannis Koutsou🇨🇾 · Colin Lauer🇺🇸

    We present a calculation of the pion and kaon Mellin moment $⟨x^3⟩$ extracted directly in lattice QCD using a three-derivative local operator. We use one ensemble of gauge configurations with two degenerate light, a strange and a charm quark ($N_f=2+1+1$) of maximally twisted mass fermions with clover improvement. The ensemble reproduces a pion mass $\sim 260$ MeV, and a kaon mass $\sim 530$ MeV. Excited-states contamination is evaluated using four values of the source-sink time separation within the range of $1.12-1.67$ fm. We use an operator that is free of mixing, and apply a multiplicative renormalization function calculated non-perturbatively. Our results are converted to the $\overline{\mathrm{MS}}$ scheme and evolved at a scale of 2 GeV, using three-loop expressions in perturbation theory. The final values are $⟨x^3{⟩}_{\pi }^{u^{+}}=0.024(18{)}_{\mathrm{stat}}(2{)}_{\mathrm{syst}}$, $⟨x^3{⟩}_K^{u^{+}}=0.035(6{)}_{\mathrm{stat}}(3{)}_{\mathrm{syst}}$, and $⟨x^3{⟩}_K^{s^{+}}=0.075(5{)}_{\mathrm{stat}}(1{)}_{\mathrm{syst}}$, where the systematic error is the uncertainty due to excited state contamination. We combine $⟨x^3⟩$ with the two lower moments to obtain the ratios $⟨x^3⟩/⟨x⟩$ and $⟨x^3⟩/⟨x^2⟩$, as well as ratios between the pion and kaon moments. In addition, we reconstruct the $x$-dependence of the pion and kaon PDFs via 2- and 3-parameter fits to our results. We find that the reconstruction is feasible and that our lattice data favor a large $x$-dependence that falls as $(1-x{)}^2$ for both the pion and kaon PDFs. We integrate the reconstructed PDFs to extract the higher moments with $4\le n\le 6$. Finally, we compare the pion and kaon PDFs, as well as the ratios of their moments, to address the effect of SU(3) flavor symmetry breaking.

    ↳ hep-lathep-exhep-phhep-thPRD(2021)·54 citations
19. 19*

    The Exact WKB and the Landau-Zener transition for asymmetry in cosmological particle production

    Seishi Enomoto🇨🇳 · Tomohiro Matsuda🇯🇵

    Cosmological particle production by a time-dependent scalar field is common in cosmology. We focus on the mechanism of asymmetry production when interaction explicitly violates symmetry and its motion is rapid enough to create particles by itself. Combining the exact WKB analysis and the Landau-Zener transition, we point out that perturbation before the non-perturbative analysis may drastically change the structure of the Stokes lines of the theory. The Exact WKB can play an important role in avoiding such discrepancies.

    ↳ hep-thastro-ph.COhep-phJHEP(2022)·21 citations
20. 20*

    $V_{ud}$ radiative corrections with lattice input

    Chien-Yeah Seng🇩🇪

    We will describe several pioneering efforts in the study of electromagnetic radiative corrections to semileptonic decay processes, with particular emphasis on the role of lattice QCD. These studies are essential for the precise extraction of the matrix element $V_{ud}$ from beta decays of pion, free neutron and $J^P=0^{+}$ nuclei, and are crucial to address several recently-emerged anomalies involving $V_{ud}$ and $V_{us}$, which may provide hints for physics beyond the Standard Model.

    ↳ hep-lathep-exhep-phnucl-ex+12 citations
21. 21*

    Hadronic light-by-light contribution to $(g-2{)}_{\mu }$ from lattice QCD: a complete calculation

    En-Hung Chao🇩🇪 · Renwick J. Hudspith🇩🇪 · Antoine Gérardin🇫🇷 · Jeremy R. Green🇨🇭 · Harvey B. Meyer🇩🇪 · Konstantin Ottnad🇩🇪

    We compute the hadronic light-by-light scattering contribution to the muon $g-2$ from the up, down, and strange-quark sector directly using lattice QCD. Our calculation features evaluations of all possible Wick-contractions of the relevant hadronic four-point function and incorporates several different pion masses, volumes, and lattice-spacings. We obtain a value of $a_{\mu }^{\text{Hlbl}}=106.8(14.7)\times 10^{-11}$ (adding statistical and systematic errors in quadrature), which is consistent with current phenomenological estimates and a previous lattice determination. It now appears conclusive that the hadronic light-by-light contribution cannot explain the current tension between theory and experiment for the muon $g-2$.

    ↳ hep-lathep-phEPJC(2021)·187 citations
22. 22*

    Find the Gap: Black Hole Population Analysis with an Astrophysically Motivated Mass Function

    Eric J. Baxter🇺🇸 · Djuna Croon🇨🇦 · Samuel D. McDermott🇺🇸 · Jeremy Sakstein🇺🇸

    We introduce a novel black hole mass function which realistically models the physics of star formation and pair instability supernova with a minimal number of parameters. Applying this to all events in the LIGO-Virgo GWTC-2 catalog, we detect a peak at M_BHMG = 74.8^{+4.3}_{-8.0} MS, followed by a break in the mass function. Repeating the analysis without the black holes from the event GW190521, we find this feature at M_BHMG = 55.4^{+3.0}_{-6.1} MS. The latter result establishes the edge of the anticipated "black hole mass gap" at a value compatible with the expectation from standard stellar structure theory, while the former result is ~ 20MS higher, which would have far-reaching implications if confirmed. Using Bayesian techniques, we establish that our mass function fits a new catalog of black hole masses approximately as well as the pre-existing phenomenological mass functions. We also remark on the implications of these results for constraining or discovering new phenomena in nuclear and particle physics.

    ↳ astro-ph.COastro-ph.IMastro-ph.SRgr-qc+1ApJL(2021)·56 citations
23. 23*

    Cross section for Bhabha and Compton scattering beyond quantum field theory

    Flora Moulin🇫🇷 · Luca Fabbri🇮🇹 · Aurélien Barrau🇫🇷

    We consider the theory of spinor fields written in polar form, that is the form in which the spinor components are given in terms of a module times a complex unitary phase respecting Lorentz covariance. In this formalism, spinors can be treated in their most general mathematical form, without the need to restrict them to plane waves. As a consequence, calculations of scattering amplitudes can be performed by employing the most general fermion propagator, and not only the free propagator usually employed in QFT. In this article, we use these quantities to perform calculations in two notable processes, the electron-positron and Compton scatterings. We show that although the methodology differs from the one used in QFT, the final results in the two examples turn out to give no correction as predicted by QFT.

    ↳ physics.gen-phhep-phInt.J.Theor.Phys.(2021)·1 citation

* 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.