New articles on hep-ph


[1] 2007.01873

Constraints on Axion-Lepton coupling from Big Bang Nucleosynthesis

In this article, we study the implications of the coupling between Axion-Like-Particles (ALPs) and Leptons to cosmology, in particular, the Big Bang Nucleosynthesis (BBN). We show that the BBN, through the constraint on the effective number of relativistic neutrino species, provides the most stringent bound on the ALP-electron interaction strength for the mass of axion between 20 keV and 1 MeV. For other values of the mass, the BBN bound complements the stellar-evolution and laboratory bounds.


[2] 2007.01893

The $ν_{R}$-philic scalar: its loop-induced interactions and Yukawa forces in LIGO observations

Right-handed neutrinos ($\nu_{R}$) are often considered as a portal to new hidden physics. It is tempting to consider a gauge singlet scalar $(\phi)$ that exclusively couples to $\nu_{R}$ via a $\nu_{R}\nu_{R}\phi$ term. Such a $\nu_{R}$-philic scalar does not interact with charged fermions at tree level but loop-induced effective interactions are inevitable, which are systematically investigated in this work. The magnitude of the loop-induced couplings coincidentally meets the current sensitivity of fifth-force searches. In particular, the loop-induced coupling to muons could be tested in the recent LIGO observations of neutron star mergers as there might be a sizable Yukawa force in the binary system mediated by the $\nu_{R}$-philic scalar.


[3] 2007.01923

Diffractive two-meson electroproduction with a nucleon and deuteron target

The diffractive electro- or photo-production of two mesons separated by a large rapidity gap gives access to generalized parton distributions (GPDs) in a very specific way. First, these reactions allow to easily access the chiral-odd transversity quark GPDs by selecting one of the produced vector meson to be transversely polarized. Second, they are only sensitive to the so-called ERBL region where GPDs are not much constrained by forward quark distributions. Third, the skewness parameter $\xi$ is not related to the Bjorken $x_\text{Bj}$ variable, but to the size of the rapidity gap. We analyze different channels ($\rho_L^0\,\rho_{L/T}, \rho^0_L\,\omega_{L/T}$ and $\rho^0_L\,\pi$ production) on nucleon and deuteron targets. The analysis is performed in the kinematical domain where a large momentum transfer from the photon to the diffractively produced vector meson introduces a hard scale (the virtuality of the exchanged hard Pomeron). This enables the description of the hadronic part of the process in the framework of collinear factorization of GPDs. We show that the unpolarized cross sections depend very much on the parameterizations of both chiral-even and chiral-odd quark distributions of the nucleon, as well as on the shape of the meson distribution amplitudes. The rates are shown to be in the range of the capacities of a future electron-ion collider.


[4] 2007.02060

Implication of Z-mediated FCNC on semileptonic decays $B_s\toφ l^+l^-$ and $B^+\to K^+ l^+ l^-$

Rare B meson decays mediated by flavour changing neutral current (FCNC) transition play interesting role to probe the flavour sector of the standard model (SM). Generally at the tree level, FCNC processes are not allowed in the SM but occurs at the loop levels. This gives an excellent hunting ground for new physics (NP). From various experimental studies it is found that the FCNC processes having quark level transition $b \to s$ are challenging. Here, we investigate different kinematic observables like forward-backward asymmetry, differential branching ratio and lepton polarization asymmetry for semileptonic rare B decay modes $B_s \to \phi l^+ l^-$ and $B^+ \to K^+ l^+ l^-$ ($l= \mu,\tau$) considering the contribution of Z-mediated FCNC. A noticeable deviation of the observables for these decay channels from the SM value is found because of non-universal $Z$-$bs$ coupling.


[5] 2007.02087

Contribution of hard photon emission to charge asymmetry in elastic (anti)lepton-proton scattering

The influence of the hard photon emission on the charge asymmetry in the (anti)lepton-proton scattering was estimated for the first time beyond the ultrarelativistic limit, while retaining the lepton mass at all steps of the calculation. This contribution, responsible for the charge asymmetry, is induced by interference between real photon emission from the lepton and the hadron. During the calculation any excited states in the intermediated proton are not considered that allow us to use the standard fermionic propagator for this particle. Another assumption consists in using the on-shell proton vertex within off-shell region. The infrared divergence extracted using Bardin-Shumeiko approach cancels by the corresponding soft part of the two-photon exchange contribution. Numerical analysis was performed within MUSE and JLab kinematic conditions.


[6] 2007.02104

Dark matter, dark photons through the observables

We analyse dark matter (DM) produced somehow in space-time is charged under the hidden $U^{\prime} (1)$ gauge symmetry and interacting with Standard Model (SM) through the scale invariance breaking sector containing dilatons and dark photons (DP). We find the solutions for DM and DP in terms of observables. The DM observable is under DP field shape influence. DP is the natural mediator between DM and the SM sectors. The phenomenology of DP physics and the registration of dark photons are discussed.


[7] 2007.02123

A possible solution of $B$ arrow $ππ$ puzzle in Z' model

The discrepancies among the measurements of branching ratios and CP asymmetries of $B$ arrow ${\pi}{\pi}$ decays such as large direct CP asymmetry for $B^0 $ arrow ${\pi}^+ {\pi}^-$ mode and large branching ratio for $B^0$ arrow ${\pi}^0 {\pi}^0$ mode originate the $B$ arrow ${\pi}{\pi}$ puzzle. According to diagrammatic approach of this $b$ arrow $d$ transition the small ratio of color-suppressed amplitude (C) to color-allowed one (T) contradicts between the standard model (SM) approach and the experimental values. To make out the ambiguity we need to scrutinize the decays with different topological amplitudes. In this paper, the decays are studied in the SM by taking different values of C/T as constraints. We find that larger ratio of C/T is explained successfully in the SM but the lower ratio is not for which new physics (NP) is needed. The NP contribution can be included in $B$ arrow ${\pi}{\pi}$ decays at tree level by Z' boson. Here, we find that Z' model can explain the puzzle by providing a good solution for lower ratio of C/T.


[8] 2007.02236

Tracing the anomalous $tqg$ and $tqγ$ flavor changing interactions at the FCC-he

We investigate the possible presence of \emph{ Flavor Changing Neutral Current (FCNC)} couplings of the top quark with gluon and photon through $e^-p\to e^-tj$ process. Focusing on disentangling the effects of different couplings that could be present, we exploit the presence of the scattered electron, the angular distribution of which is sensitive to the type of coupling involved. Further, we demonstrate the potential of electron beam polarisation in distinguishing the left-handed and right-handed couplings of both gluon and photon separately. Considering an $e^-p$ collider of beam energies of $E_{e(p)} = 60~(50000)$~GeV at 2~ab$^{-1}$ integrated luminosity, couplings can be probed at the level of $10^{-2}$ with the corresponding branching fractions of $BR(t\to u\gamma)\le 4 - 7 \times 10^{-6}$ and $BR(t\to c\gamma) \le 1-2 \times 10^{-5}$, depending on if the coupling is right-handed or left-handed. The corresponding limits on the gluon couplings lead to $BR(t\to ug)\le 1.7 \times 10^{-6}$ and $BR(t\to cg) \le 3-4 \times 10^{-5}$.


[9] 2007.02263

A universal non-resonant explanation to charmoniumlike structures $Z_c(3885)$ and $Z_c(4025)$

Different from the usual tetraquark assignment to charged $Z_c(3885)$ and $Z_c(4025)$ charmoniumlike structures, in this letter we propose a universal non-resonant explanation to decode these $Z_c$'s, which is based on a special dynamical behavior of $e^+e^-\to D^{(*)}\bar{D}^*\pi$. Our study shows that $Z_c(3885)$ and $Z_c(4025)$ are only the reflection from the $P$-wave charmed meson $D_1(2420)$ involved in $e^+e^-\to D^{(*)}\bar{D}^*\pi$. Obviously, the present work provides a unique perspective, which can be examined by future experiments like BESIII and BelleII.


[10] 2007.02273

Charm meson couplings in hard-wall Holographic QCD

The four-flavor hard-wall holographic QCD is studied to evaluate the couplings of $(D^{_{-(*-)}}, \bar{D}^{_0}, a_1^{_-})$, $(D^{_{-(*-)}}, \bar{D}^{_0}, b_1^{_-})$, $(D_{s}^{_{-(*-)}},\bar{D}^{_0}, K_{1A}^{_-})$, $(D_s^{_{-(*-)}}, \bar{D}^{_0}, K_{1B}^{_{-(*-)}})$, $(D_s^{_{+(*+)}}, D^{_+}, K_{1A}^{_0})$, $(D_s^{_{+(*+)}}, D^{_+}, K_{1B}^{_0})$, $(D^{_{-(*-)}}, \bar{D}^{_{0(*0)}}, \rho^{_-})$, $(D_s^{_{-(*-)}}, \bar{D}^{_{0(*0)}}, K^{_{*-}})$, $(D^{_{0(*0)}}, \bar{D}^{_{0(*0)}}, \psi)$, $(D_1^{_-}, \bar{D}_1^{_0}, \pi^{_-})$, $(D_{s1}^{_-}, \bar{D}_1^{_0}, K^{_{-}})$, $(D_1^{_0}, \bar{D}_1^{_0}, \eta_c)$, $(\psi, D^{_{0(*0)}}, D^{_+}, \pi^{_-})$, $(\psi, D^{_{0(*0)}}, \bar{D}^{_0}, \pi^{_0})$, $(\psi, D_{s}^{_{+(*+)}}, D^{_-}, K^{_0})$, $(\psi, D^{_{0(*0)}}, D^{_+}, a_1^{_-})$, $(\psi, D^{_{0(*0)}}, D^{_+}, b_1^{_-})$, $(\psi, D_s^{_{+(*+)}}, D^{_-}, K_{1B}^{_0})$ and $(\psi, D_s^{_{+(*+)}}, D^{_-}, K_{1B}^{_0})$ vertices. Moreover, the values of the masses of $D^{_{0(*0)}}$, $D_s^{_{-(*-)}}$, $\omega$, $\psi$, $D_1^{_0}$, $D_1^{_{-}}$, $K^0$, $\eta_{c}$, $D_{s1}^{_-}$ and $\chi_{_{c1}}$ as well as the decay constant of $\pi^-$, $D^{_{-(*-)}}$, $K^-$, $\rho^-$, $D_1^{_-}$ , $a_1^-$ and $D_s^{_{-(*-)}}$ are estimated in this study. A comparison is also made between our results and the experimental values of the masses and decay constants. Our results for strong couplings are also compared with the 3PSR and LCSR predictions.


[11] 2007.02327

Constraints on the quark mixing matrix with vector-like quarks

While a chiral fourth generation of quarks is almost ruled out from the data on Higgs boson production and decay at the Large Hadron Collider, vector-like quarks are still a feasible option to extend the fermionic sector of the Standard Model. Such an extension does not suffer from any anomalies and easily passes the constraints coming from oblique electroweak parameters. We consider such minimal extensions with $SU(2)$ singlet and doublet vector-like quarks that may mix with one, or at the most two, of the Standard Model quarks. Constraints on the new mixing angles and phases are obtained from several $\Delta B = 1$ and $\Delta B = 2$ processes.


[12] 2007.02504

$SU(3)$ Flavor Symmetry for Weak Hadronic Decays of ${\bf B}_{bc}$ Baryons

Baryons with a heavy c-quark or a heavy b-quark and also two c-quarks have been discovered. These states are expected in QCD and therefore provide a test for the theory. There should be double beauty baryons, and also an intriguing possibility that baryons ${\bf B}_{bc}$ with a c-quark, a b-quark. These states are yet to be discovered. The main decay modes of ${\bf B}_{bc}$ are expected to be weak processes from theoretical understanding of their mass spectrum. These decay modes can provide crucial information about these heavy baryons ${\bf B}_{bc}$. We analyze two body hadronic weak decays for ${\bf B}_{bc}$ using $SU(3)$ flavor symmetry. Any one of the $c$ and $b$ decays will induce ${\bf B}_{bc}$ to decay. We find that the Cabibbo allowed decays ${\bf B}_{bc} \to {\bf B}_b + M$ due to $c \to s u \bar d$ can be crucial for exploration. The LHC may have the sensitivity to discover such decays. Other ${\bf B}_{bc}$ decays due to $b \to c q' \bar q$ are sub-leading. Several relations among branching ratios are obtained which can be used to test flavor $SU(3)$ symmetry.


[13] 2007.02558

Branching Fractions and CP Violation in $B^-\to K^+K^-π^-$ and $B^-\to π^+π^-π^-$ Decays

We present in this work a study of tree-dominated charmless three-body decays of $B$ mesons, $B^-\to K^+K^-\pi^-$ and $B^-\to\pi^+\pi^-\pi^-$, within the factorization approach. The main results are: (i) There are two distinct sources of nonresonant contributions: one arises from the $b\to u$ tree transition and the other from the nonresonant matrix element of scalar densities $\langle M_1M_2|\bar q_1 q_2|0\rangle^{\rm NR}$. It turns out that even for tree-dominated three-body decays, dominant nonresonant contributions originate from the penguin diagram rather than from the $b\to u$ tree process, as implied by the large nonresonant component observed recently in the $\pi^- K^+$ system which accounts for one third of the $B^-\to K^+K^-\pi^-$ rate. (ii) The calculated branching fraction of $B^-\to f_2(1270)\pi^-\to K^+K^-\pi^-$ is smaller than the LHCb by a factor of $\sim 7$ in its central value, but the predicted $\B(B^-\to f_2(1270)\pi^-\to\pi^+\pi^-\pi^-)$ is consistent with the data. Branching fractions of $B^-\to f_2(1270)\pi^-$ extracted from the LHCb measurements of these two processes also differ by a factor of seven! Therefore, it is likely that the $f_2(1270)$ contribution to $B^-\to K^+K^-\pi^-$ is largely overestimated experimentally. Including $1/m_b$ power corrections from penguin annihilation inferred from QCD factorization (QCDF), a sizable CP asymmetry of 32\% in the $f_2(1270)$ component agrees with experiment. (iii) A fraction of 5\% for the $\rho(1450)$ component in $B^-\to\pi^+\pi^-\pi^-$ is in accordance with the theoretical expectation. However, a large fraction of 30\% in $B^-\to K^+K^-\pi^-$ is entirely unexpected. This issue needs to be clarified in the future.


[14] 2007.02655

U(1) mixing and the Weak Gravity Conjecture

Tiny values for gauge couplings of dark photons allow to suppress their kinetic mixing with ordinary photons. We point out that the Weak Gravity Conjecture predicts consequently low ultraviolet cut-offs where new degrees of freedom might appear. In particular, a mixing angle of $\mathcal{O}(10^{-15})$, required in order to fit the excess reported by XENON1T, corresponds to new physics below $\mathcal{O}(100)$ TeV, thus accessible at a Future Circular Collider. We show that possible realizations are provided by compactifications with six large extra dimensions and a string scale of order $\mathcal{O}(100)$ TeV.


[15] 2007.02822

Probing topological order of QCD at Electron Ion Collider

The idea that the nuclear matter may posses long range topological order is supported by the theory and the lattice calculations. At high temperature this order is instrumental in producing anomalous phenomena such as the Chiral Magnetic Effect. In the cold nuclear matter it affects the gluon distribution in the nuclear wave function at low $x$. The effect of the topological order is encapsulated in the unintegrated gluon distribution functions which are proportional, at the leading order, to the square of the gluon propagator at finite topological charge density. It is argued that the Electron Ion Collider is well suited to study the topological order of the cold nuclear matter.


[16] 2007.02898

Dark Matter $Z^\prime$ and XENON1T Excess from $U(1)_X$ Extended Standard Model

A gauged $U(1)_X$ symmetry appended to the Standard Model (SM) is particularly well-motivated since it can account for the light neutrino masses by the seesaw mechanism, explain the origin of baryon asymmetry of the universe via leptogenesis, and help implement successful cosmological inflation with the $U(1)_X$ breaking Higgs field as the inflaton. In this framework, we propose a light dark matter (DM) scenario in which the $U(1)_X$ gauge boson $Z^\prime$ behaves as a DM particle in the universe. We discuss how this scenario with $Z^\prime$ mass of a few keV and a $U(1)_X$ gauge coupling $g_X \simeq 10^{-16}$ can nicely fit the excess in the electronic recoil energy spectrum recently reported by the XENON1T collaboration. In order to reproduce the observed DM relic density in the presence of such a tiny gauge coupling, we propose an extension of the model to a two-component DM scenario. The $Z^\prime$ DM density can be comparable to the observed DM density by the freeze-in mechanism through the coupling of $Z^\prime$ boson to a partner Higgs-portal scalar DM with a large $U(1)_X$ charge.


[17] 2007.02131

Notes on lattice observables for parton distributions: nongauge theories

We review recent theoretical developments concerning the definition and the renormalization of equal-time correlators that can be computed on the lattice and related to Parton Distribution Functions (PDFs) through a factorization formula. We show how these objects can be studied and analyzed within the framework of a nongauge theory, gaining insight through a one-loop computation. We use scalar field theory as a playground to revise, analyze and present the main features of these ideas, to explore their potential, and to understand their limitations for extracting PDFs. We then propose a framework that would allow to include the available lattice QCD data in a global anlysis to extract PDFs.


[18] 2007.02213

Constraining Primordial Black Holes with Dwarf Galaxy Heating

Black holes formed in the early universe, prior to the formation of stars, can exist as dark matter and also contribute to the black hole merger events observed in gravitational waves. We set a new limit on the abundance of primordial black holes (PBHs) by considering interactions of PBHs with the interstellar medium, which result in the heating of gas. We examine generic heating mechanisms, including emission from the accretion disk, dynamical friction, and disk outflows. Using the data from the Leo T dwarf galaxy, we set a new cosmology-independent limit on the abundance of PBHs in the mass range $\mathcal{O}(1) M_{\odot}-10^7 M_{\odot}$.


[19] 2007.02276

Probing axion dark matter with 21cm fluctuations from minihalos

If the symmetry breaking inducing the axion occurs after the inflation, the large axion isocurvature perturbations can arise due to a different axion amplitude in each causally disconnected patch. This causes the enhancement of the small-scale density fluctuations which can significantly affect the evolution of structure formation. The epoch of the small halo formation becomes earlier and we estimate the abundance of those minihalos which can host the neutral hydrogen atoms to result in the 21cm fluctuation signals. We find that the future radio telescopes, such as the SKA, can put the axion mass bound of order $m_a \gtrsim 10^{-13}$ eV for the simple temperature-independent axion mass model, and the bound can be extended to of order $m_a \gtrsim 10^{-8}$eV for a temperature-dependent axion mass.


[20] 2007.02395

Gravitational Particle Production in Loop Quantum Cosmology

We investigate the gravitational particle production in the bounce phase of Loop Quantum Cosmology (LQC). We perform both analytical and numerical analysis of the particle production process in a LQC scenario with Bunch-Davies vacuum initial condition in the contracting phase. We obtain that if we extend the validity of the dressed metric approach beyond the limit of small backreaction in which it is well justified, this process would lead to a radiation dominated phase in the pre-inflationary phase of LQC. Our results indicate that the test field approximation, which is required in the truncation scheme used in the dressed metric approach, might not be a valid assumption in a LQC scenario with such initial conditions.


[21] 2007.02841

On-shot diagnostic of electron beam-laser pulse interaction based on stochastic quantum radiation reaction

Ultrarelativistic electron beam-laser pulse scattering experiments are the workhorse for the investigation of QED and of possible signatures of new physics in the still largely unexplored strong-field regime. However, shot-to-shot fluctuations both of the electron beam and of the laser pulse parameters render it difficult to discern the dynamics of the interaction. Consequently, the possibility of benchmarking theoretical predictions against experimental results, which is essential for validating theoretical models, is severely limited. Here we show that the stochastic nature of quantum emission events provides a unique route to the on-shot diagnostic of the electron beam-laser pulse interaction, therefore paving the way for accurate measurements of strong-field QED effects.