Tue·Feb 16, 2021Tuesday·February 16, 2021

1. 01*

   The Minimal Flavor Structure from Decomposition of the Fermion Mass Matrix

   Ying Zhang🇨🇳

   The minimal flavor structures for both quarks and leptons are proposed to address fermion mass hierarchy and flavor mixings by bi-unitary decomposition of the fermion mass matrix. The real matrix ${\mathbf{M}}_0^f$ is completely responsive to family mass hierarchy, which is expressed by a close-to-flat matrix structure. The left-handed unitary phase ${\mathbf{F}}_L^f$ provides the origin of CP violation in quark and lepton mixings, which can be explained as a quantum effect between Yukawa interaction states and weak gauge states. The minimal flavor structure is realized by just 10 parameters without any redundancy, corresponding to 6 fermion masses, 3 mixing angles and 1 CP violation in the quark/lepton sector. This approach provides a general flavor structure independent of the specific quark or lepton flavor data. We verify the validation of the flavor structure by reproducing quark/lepton masses and mixings. Some possible scenarios that yield the flavor structure are also discussed.

   hep-phNPB(2022)·4 citations
2. 02*

   Heavy quark transport in an anisotropic hot QCD medium: Collisional and Radiative processes

   Jai Prakash🇮🇳 · Manu Kurian🇮🇳 · Santosh K. Das🇮🇳 · Vinod Chandra🇮🇳

   The impact of momentum anisotropy on the heavy quark transport coefficients due to collisional and radiative processes in the QCD medium has been studied within the ambit of kinetic theory. Anisotropic aspects (momentum) are incorporated into the heavy quark dynamics through the non-equilibrium momentum distribution function of quarks, antiquarks, and gluons. These non-equilibrium distribution functions that encode the physics of momentum anisotropy and turbulent chromo-fields have been obtained by solving the ensemble-averaged diffusive Vlasov-Boltzmann equation. The momentum dependence of heavy quark transport coefficients in the medium is seen to be sensitive to the strength of the anisotropy for both collisional and radiative processes. In addition, the collisional and radiative energy loss of the heavy quark in the anisotropic hot QCD medium have been analyzed. The effects of anisotropy on the drag and diffusion coefficients are observed to have a visible impact on the nuclear suppression factor both at the RHIC and LHC.

   hep-phnucl-thPRD(2021)·28 citations
3. 03*

   Detecting the polarization in ${\chi }_{cJ}\to \varphi \varphi$ decays to probe hadronic loop effect

   Qi Huang🇨🇳 · Jun-Zhang Wang🇨🇳 · Rong-Gang Ping🇨🇳 · Xiang Liu🇨🇳

   In this work, we propose that detecting the polarization information of ${\chi }_{cJ}\to \varphi \varphi (J=0,1,2)$ can be as good test of the role of hadronic loop effect on these decays. Our results shows that the obtained ratios of helicity amplitudes are quite stable, which are $|F_{1,1}^{(0)}/F_{0,0}^{(0)}|\approx 0.359$, $|F_{1,0}^{(1)}/F_{0,1}^{(1)}|=1$, $|F_{1,1}^{(1)}/F_{0,1}^{(1)}|=0$, $|F_{1,0}^{(2)}|/|F_{0,0}^{(2)}|=|F_{0,1}^{(2)}|/|F_{0,0}^{(2)}|\approx 1.285,|F_{1,-1}^{(2)}|/|F_{0,0}^{(2)}|=|F_{-1,1}^{(2)}|/|F_{0,0}^{(2)}|\approx 5.110$ and $|F_{-1,-1}^{(2)}|/|F_{0,0}^{(2)}|=|F_{1,1}^{(2)}|/|F_{0,0}^{(2)}|\approx 0.465$. By adopting these predicted ratios, we further generate Monte-Carlo events of moments $⟨t_{ij}⟩$, which are directly related to the determination of helicity amplitudes. We suggest further experiments like BESIII and Belle II to perform an analysis on the polarizations of the ${\chi }_{cJ}\to \varphi \varphi$ process in the future, which is important to understand the underlying decay mechanism existing in ${\chi }_{cJ}$ decays.

   hep-phhep-exPRD(2021)·12 citations
4. 04*

   Electroweak monopoles and magnetic dumbbells in grand unified theories

   George Lazarides🇬🇷 · Qaisar Shafi🇺🇸

   We use the $SU(5)$ model to show the presence in grand unified theories of an electroweak monopole and a magnetic dumbbell ("meson") made up of a monopole-antimonopole pair connected by a $Z$-magnetic flux tube. The monopole is associated with the spontaneous breaking of the weak $SU(2{)}_L$ gauge symmetry by the induced vacuum expectation value of a heavy scalar $SU(2{)}_L$ triplet with zero weak hypercharge contained in the adjoint Higgs 24-plet. This monopole carries a Coulomb magnetic charge of $(3/4)(2\pi /e)$ as well as $Z$-magnetic charge, where $2\pi /e$ denotes the unit Dirac magnetic charge. Its total magnetic charge is $\sqrt{3/8}(4\pi /e)$, which is in agreement with the Dirac quantization condition. The monopole weighs about 700 GeV, but because of the attached $Z$-magnetic tube it exists, together with the antimonopole, in a magnetic dumbbell configuration whose mass is expected to lie in the TeV range. The presence of these topological structures in $SU(5)$ and $SO(10)$ and in their supersymmetric extensions provides an exciting new avenue for testing these theories in high-energy colliders.

   hep-phhep-thPRD(2021)·10 citations
5. 05*

   Exceptional regions of the 2HDM parameter space

   Howard E. Haber🇺🇸 · Joao P. Silva🇵🇹

   The exceptional region of the parameter space (ERPS) of the two Higgs doublet model (2HDM) is defined to be the parameter regime where the scalar potential takes on a very special form. In the standard parameterization of the 2HDM scalar potential with squared mass parameters $m_{11}^2$, $m_{22}^2$, $m_{12}^2$, and dimensionless couplings, ${\lambda }_1$, ${\lambda }_2$, $\dots ,{\lambda }_7$, the ERPS corresponds to ${\lambda }_1={\lambda }_2$, ${\lambda }_7=-{\lambda }_6$, $m_{11}^2=m_{22}^2$ and $m_{12}^2=0$, corresponding to a scalar potential with an enhanced generalized CP symmetry called GCP2. Many special features persist if ${\lambda }_1={\lambda }_2$ and ${\lambda }_7=-{\lambda }_6$ are retained while allowing for $m_{11}^2\ne m_{22}^2$ and/or $m_{12}^2\ne 0$, corresponding to a scalar potential with a softly-broken GCP2 symmetry, which we designate as the ERPS4. In this paper, we examine many of the special features of the ERPS4, as well as even more specialized cases within the ERPS4 framework in which additional constraints on the scalar potential parameters are imposed. By surveying the landscape of the ERPS4, we complete the classification of 2HDM scalar potentials that exhibit an exact Higgs alignment (where the tree-level couplings of one neutral scalar coincide with those of the Standard Model Higgs boson), due to a residual symmetry that is unbroken in the vacuum. One surprising aspect of the ERPS4 is the possibility that the scalar sector is CP-conserving despite the presence of a complex parameter of the scalar potential whose complex phase cannot be removed by separate rephasings of the two scalar doublet fields. The significance of the ERPS4 regime for custodial symmetry is also discussed, and the cases where a custodial symmetric 2HDM scalar potential preserves an exact Higgs alignment are elucidated.

   hep-phPRD(2021)·12 citations
6. 06*

   Revisiting the nature of the $P_c$ pentaquarks

   Meng-Lin Du🇩🇪 · Vadim Baru🇩🇪 · Feng-Kun Guo🇨🇳 · Christoph Hanhart🇩🇪 · Ulf-G. Meißner🇩🇪 · José A. Oller🇪🇸 · Qian Wang🇨🇳

   The nature of the three narrow $P_c$ states, i.e., $P_c(4312)$, $P_c(4440)$ and $P_c(4457)$, is under intense discussion since their discovery from the updated analysis by LHCb. In this work we extend our previous coupled-channel approach [Phys. Rev. Lett. \bf{124}, 072001 (2020)] by including the ${\Lambda }_c{\bar{D}}^{(\ast )}$ and ${\eta }_{c}p$ as explicitly in addition to the $J/\psi p$, as required by unitarity and heavy quark spin symmetry (HQSS). Since inelastic parameters are very badly constrained by the current data, three schemes are considered: (a) scheme I with pure contact interactions and without the ${\Lambda }_c{\bar{D}}^{(\ast )}$ interactions, (b) scheme II, where the one-pion exchange is added to scheme I, and (c) scheme III, where the ${\Lambda }_c{\bar{D}}^{(\ast )}$ are included in addition. It is shown that to obtain cutoff independent results, OPE in the multichannel system is to be supplemented with $S$-$D$ mixing contact terms. We demonstrate that the experimental data for the $J/\psi p$ invariant mass distribution are consistent with the interpretation of the $P_c(4312)$ and $P_c(4440)/P_c(4457)$ as ${\Sigma }_c\bar{D}$ and ${\Sigma }_c{\bar{D}}^{\ast }$ hadronic molecules, respectively, and that the data show clear evidence for a new narrow $P_c(4380)$, as a ${\Sigma }_c^{\ast }\bar{D}$ molecule, which should exist as a consequence of HQSS. While two equally good solutions are found in scheme I, only one of these solutions with the quantum numbers of the $P_c(4440)$ and $P_c(4457)$ being $J^P=3/2^{-}$ and $1/2^{-}$, respectively, survives the requirement of regulator independence once the OPE is included. Moreover, we predict the line shapes in the elastic and inelastic channels and demonstrate that those related to the $P_c(4440)$ and the $P_c(4457)$ in the corresponding ${\Sigma }_c^{(\ast )}\bar{D}$ and ${\eta }_{c}p$ mass distributions allow one to confirm the quantum numbers given above, once the data are available.

   hep-phJHEP(2021)·120 citations
7. 07*

   Bound states of the Yukawa potential from hidden supersymmetry

   M. Napsuciale🇲🇽 · S. Rodríguez🇲🇽

   In this work, we present a phenomenological study of the complete analytical solution to the bound eigenstates and eigenvalues of the Yukawa potential obtained previously using the hidden supersymmetry of the system and a systematic expansion of the Yukawa potential in terms of $\delta =a_0/D$, where $a_0$ is the Bohr radius and $D$ is the screening length. The eigenvalues, ${ϵ}_{nl}(\delta )$, are given in the form of Taylor series in $\delta$ which can be systematically calculated to the desired order ${\delta }^k$. Coulomb $l$-degeneracy is broken by the screening effects and, for a given $n$, ${ϵ}_{nl}(\delta )$ is larger for higher values of $l$ which causes the crossing of levels for $n\ge 4$. The convergence radius of the Taylor series can be enlarged up to the critical values using the Padé approximants technique which allows us to calculate the eigenvalues with high precision in the whole rage of values of $\delta$ where bound states exist, and to reach a precise determination of the critical screening lengths, ${\delta }_{nl}$. Eigenstates have a form similar to the solutions of the Coulomb potential, with the associated Laguerre polynomials replaced by new polynomials of order ${\delta }^k$ with $r$-dependent coefficients which, in turn, are polynomials in $r$. In general we find sizable deviations from the Coulomb radial probabilities only for screening lengths close to their critical values. We use these solutions to find the squared absolute value at the origin of the wave function for $l=0$, and their derivatives for $l=1$, for the lowest states, as functions of $\delta$, which enter the phenomenology of dark matter bound states in dark gauge theories with a light dark mediator.

   hep-phphysics.plasm-phquant-phPTEP(2021)·7 citations
8. 08*

   Phenomenology of fermion dark matter as neutrino mass mediator with gauged B-L

   Carlos Alvarado🇨🇳 · Cesar Bonilla🇨🇱 · Julio Leite🇧🇷 · José W. F. Valle🇪🇸

   We analyze a model with unbroken B-L gauge symmetry where neutrino masses are generated at one loop, after spontaneous breaking of a global U(1) symmetry. These symmetries ensure dark matter stability and the Diracness of neutrinos. Within this context, we examine fermionic dark matter. Consistency between the required neutrino mass and the observed relic abundance indicates dark matter masses and couplings within the reach of direct detection experiments.

   hep-phhep-exPLB(2021)·20 citations
9. 09*

   Thermal quarks and gluon propagators in two-color dense QCD

   Toru Kojo🇨🇳 · Daiki Suenaga🇯🇵

   We study Landau gauge gluon propagators in two-color QCD at finite quark chemical potential (${\mu }_q$) and temperature ($T$). We include medium polarization effects at one-loop by quarks into massive gluon propagators, and compared the analytic results with the available lattice data. We particularly focus on the high density phase of color-singlet diquark condensates whose critical temperature is $\sim 100$ MeV with weak dependence on ${\mu }_q$. At zero temperature the color singlet condensates protect the IR limit of electric and magnetic gluon propagators from the medium screening effects. At finite temperature, this behavior remains true for the magnetic sector, but the electric screening mass should be generated by thermal, and hence gapless, particles which are unbound from the diquark condensates. Treating thermal excitations as quasi-quarks, we found that the electric screening develops too fast compared to the lattice results. Beyond the critical temperature for diquark condensates the analytic results are consistent with the lattice results.

   hep-phastro-ph.HEhep-latnucl-thPRD(2021)·24 citations
10. 10*

    The $\bar{B}\to \pi$ form factors from QCD and their impact on $|V_{ub}|$

    Domagoj Leljak🇭🇷 · Blaženka Melić🇭🇷 · Danny van Dyk🇩🇪

    We revisit light-cone sum rules with pion distribution amplitudes to determine the full set of local $B\to \pi$ form factors. To this end, we determine all duality threshold parameters from a Bayesian fit for the first time. Our results, obtained at small momentum transfer $q^2$, are extrapolated to large $q^2$ where they agree with precise lattice QCD results. We find that a modification to the commonly used BCL parametrization is crucial to interpolate the scalar form factor between the two $q^2$ regions. We provide numerical results for the form factor parameters -- including their covariance -- based on simultaneous fit of all three form factors to both the sum rule and lattice QCD results. Our predictions for the form factors agree well with measurements of the $q^2$ spectrum of the semileptonic decay ${\bar{B}}^0\to {\pi }^{+}{\ell }^{-}\bar{\nu }$. From the world average of the latter we obtain $|V_{ub}|=(3.77\pm 0.15)\cdot 10^{-3}$, which is in agreement with the most recent inclusive determination at the $1\sigma$ level.

    hep-phJHEP(2021)·65 citations
11. 11*

    Higgs alignment and the top quark

    Estia J. Eichten🇺🇸 · Kenneth Lane🇺🇸

    There is a surprising connection between the top quark and Higgs alignment in Gildener-Weinberg multi-Higgs doublet models. Were it not for the top quark and its large mass, the coupling of the 125 GeV Higgs boson $H$ to gauge bosons and fermions would be indistinguishable from those of the Standard Model Higgs. The top quark's coupling to a single Higgs doublet breaks this perfect alignment in higher orders of the Coleman-Weinberg loop expansion of the effective potential. But the effect is still small, $<\mathcal{O}(1\%)$, and probably experimentally inaccessible.

    hep-phhep-exPRD(2021)·10 citations
12. 12*

    Small size instanton contributions to the quark quasi-PDF and matching kernel

    Yizhuang Liu🇨🇳 · Ismail Zahed🇺🇸

    We investigate the non-perturbative contribution of instantons to current matching kernels used in the context of the large momentum effective theory (LaMET). We derive explicitly these contributions using first principle semi-classical calculus for the unpolarized and polarized quark parton distributions and the matching kernel, and show that they are part of a trans-series expansion. These contributions are substantial at current lattice matching momenta.

    hep-phhep-lat7 citations
13. 13*

    Strong decays of the low-lying bottom strange baryons

    Hui-Zhen He🇨🇳 · Wei Liang🇨🇳 · Qi-Fang Lü🇨🇳 · Yu-Bing Dong🇨🇳

    In this work, the strong decay behaviors of the $\lambda -$mode low-lying ${\Xi }_b$ and ${\Xi }_b^{\prime }$ baryons are investigated within the ${}^3{P}_0$ model. Our results suggest that all of the low-lying ${\bar{3}}_F$ states ${\Xi }_b(2S)$, ${\Xi }_b(1P)$, and ${\Xi }_b(1D)$ have small decay widths of less than 20 MeV, and these states have good potentials to be observed in the ${\Xi }_b^{\prime }\pi$ and ${\Xi }_b^{\prime \ast }\pi$ invariant masses. Further, most of the $6_F$ multiplets are relatively narrow and may decay into the ${\Xi }_b\pi$, ${\Xi }_b^{\prime }\pi$, ${\Xi }_b^{\prime \ast }\pi$, and ${\Lambda }_b\bar{K}$ final states. Considering the masses and strong decay behaviors, we can assign the newly observed ${\Xi }_b(6100)$ resonance as the ${\Xi }_b(1P)$ state with $J^P=3/2^{-}$ and interpret the ${\Xi }_b(6227)$ structure as the $J^P=3/2^{-}$ ${\Xi }_b^{\prime }(1P)$ state with a proper mixing angle. We expect that our predictions for these excited bottom strange baryons will provide helpful information for future experimental research.

    hep-phhep-exnucl-thSCPMA(2021)·29 citations
14. 14*

    Differential equations and Feynman integrals

    A.V. Kotikov🇷🇺

    The role of differential equations in the process of calculating Feynman integrals is reviewed. An example of a diagram is given for which the method of differential equations was introduced, the properties of the inverse-mass-expansion coefficients are shown, and modern methods based on differential equations are considered.

    hep-ph17 citations
15. 15*

    Fermion Mass Hierarchies, Large Lepton Mixing and Residual Modular Symmetries

    P. P. Novichkov🇮🇹 · J. T. Penedo🇵🇹 · S. T. Petcov🇮🇹

    In modular-invariant models of flavour, hierarchical fermion mass matrices may arise solely due to the proximity of the modulus $\tau$ to a point of residual symmetry. This mechanism does not require flavon fields, and modular weights are not analogous to Froggatt-Nielsen charges. Instead, we show that hierarchies depend on the decomposition of field representations under the residual symmetry group. We systematically go through the possible fermion field representation choices which may yield hierarchical structures in the vicinity of symmetric points, for the four smallest finite modular groups, isomorphic to $S_3$, $A_4$, $S_4$, and $A_5$, as well as for their double covers. We find a restricted set of pairs of representations for which the discussed mechanism may produce viable fermion (charged-lepton and quark) mass hierarchies. We present two lepton flavour models in which the charged-lepton mass hierarchies are naturally obtained, while lepton mixing is somewhat fine-tuned. After formulating the conditions for obtaining a viable lepton mixing matrix in the symmetric limit, we construct a model in which both the charged-lepton and neutrino sectors are free from fine-tuning.

    hep-phhep-thJHEP(2021)·127 citations
16. 16*

    Dark matter, $Z^{\prime }$, vector-like quark at the LHC and $b\to s\mu \mu$ anomaly

    Wei Chao🇨🇳 · Hongxin Wang🇨🇳 · Lei Wang🇨🇳 · Yang Zhang🇨🇳

    Combining the $b\to s{\mu }^{+}{\mu }^{-}$ anomaly and dark matter observables, we study the capability of LHC to test dark matter, $Z^{\prime }$, and vector-like quark. We focus on a local $U(1{)}_{L_{\mu }-L_{\tau }}$ model with a vector-like $SU(2{)}_L$ doublet quark $Q$ and a complex singlet scalar whose lightest component $X_I$ is a candidate of dark matter. After imposing relevant constraints, we find that the $b\to s{\mu }^{+}{\mu }^{-}$ anomaly and the relic abundance of dark matter favor $m_{X_I}<350$ GeV and $m_{Z^{\prime }}<450$ GeV for $m_Q<$ 2 TeV and $m_{X_R}<$ 2 TeV (the heavy partner of $m_{X_I}$). The current searches for jets and missing transverse momentum at the LHC sizably reduce the mass ranges of the vector-like quark, and $m_Q$ is required to be larger than 1.7 TeV. Finally, we discuss the possibility of probing these new particles at the high luminosity LHC via the QCD process $pp\to D\bar{D}$ or $pp\to U\bar{U}$ followed by the decay $D\to s(b)Z^{\prime }{X}_I$ or $U\to u(c)Z^{\prime }{X}_I$ and then $Z^{\prime }\to {\mu }^{+}{\mu }^{-}$. Taking a benchmark point of $m_Q$=1.93 TeV, $m_{Z^{\prime }}=170$ GeV, and $m_{X_I}=$ 145 GeV, we perform a detailed Monte Carlo simulation, and find that such benchmark point can be accessible at the 14 TeV LHC with an integrated luminosity 3000 fb${}^{-1}$.

    hep-phCPC(2021)·7 citations
17. 17*

    Comment on "OPE and quark-hadron duality for two-point functions of tetraquark currents in $1/N_c$ expansion"

    Zhi-Gang Wang🇨🇳

    Without excluding the contributions of factorizable Feynman diagrams in the color space to the QCD sum rules by hand, we cannot obtain the conclusion that the factorizable parts of the operator product expansion series cannot have any relationship to the possible tetraquark bound states. The tetraquark couplings $f_T$ are of the order $\mathcal{O}(N_c)$ rather than of the order $\mathcal{O}(N_c^0)$ in the large $N_c$ limit, the conclusion "a possible exotic tetraquark state may appear only in $N_c$-subleading contributions to the QCD Green functions" is a paradox.

    hep-ph5 citations
18. 18*

    Some Aspects of the Theory of Heavy Ion Collisions

    Francois Gelis🇫🇷

    We review the theoretical aspects relevant in the description of high energy heavy ion collisions, with an emphasis on the learnings about the underlying QCD phenomena that have emerged from these collisions.

    hep-phnucl-thRept.Prog.Phys.(2021)·32 citations
19. 19*

    Fully Differential Higgs Boson Production to Third Order in QCD

    X. Chen🇨🇭 · T. Gehrmann🇨🇭 · E. W. N. Glover🇬🇧 · A. Huss🇨🇭 · B. Mistlberger🇺🇸 · A. Pelloni🇳🇱

    We present fully differential predictions for the production cross section of a Higgs boson via the gluon fusion mechanism at next-to-next-to-next-to leading order (N${}^3$LO) in QCD perturbation theory. To perform our calculation we apply the Projection-to-Born method for the first time to the calculation of the non-factorising production of a colorless final state at the LHC at N${}^3$LO. We predict differential distributions for the two photon final state produced by the decay of the Higgs boson and apply fiducial cuts on the photon rapidities and momenta. The N${}^3$LO corrections to these differential distributions have complex features and are in part larger than the inclusive N${}^3$LO corrections to the production cross section. Overall, we observe that the inclusion of the N${}^3$LO QCD corrections significantly reduces the perturbative uncertainties and leads to a stabilisation of the perturbative expansion.

    hep-phPRL(2021)·113 citations
20. 20*

    Higgs boson self-coupling constraints from single Higgs, double Higgs and Electroweak measurements

    Giuseppe Degrassi (1 and 2)🇮🇹 · Biagio Di Micco (1 and 2)🇮🇹 · Pier Paolo Giardino (3)🇪🇸 · Eleonora Rossi (4) ( (1) Università degli Studi di Roma Tre, Roma, Italy (2) INFN sezione di Roma Tre, Roma, Italy (3) Instituto Galego de Física de Altas Enerxías, Universidade de Santiago de Compostela, Galicia, Spain, (4) LAPP, Université Grenoble Alpes, Université Savoie Mont Blanc, CNRS/IN2P3, Annecy, France)🇫🇷

    We set constraints on the trilinear Higgs boson self-coupling, ${\lambda }_3$, by combining the information coming from the $W$ mass and leptonic effective Weinberg angle, electroweak precision observables, with the single Higgs boson analyses targeting the $\gamma \gamma ,Z{Z}^{\ast },W{W}^{\ast },{\tau }^{+}{\tau }^{-}$ and $\bar{b}b$ decay channels and the double Higgs boson analyses in the $b\bar{b}b\bar{b},b\bar{b}b{\tau }^{+}{\tau }^{-}$ and $b\bar{b}b\gamma \gamma$ decay channels, performed by the ATLAS collaboration. With the assumption that the new physics affects only the Higgs potential, values outside the interval $-1.8{\lambda }_3^{\mathrm{SM}}<{\lambda }_3<9.2{\lambda }_3^{\mathrm{SM}}$ are excluded at $95\%$ confidence level. With respect to similar analyses that do not include the information coming from the electroweak precision observables our analysis shows a stronger constraint on both positive and negative values of ${\lambda }_3$.

    hep-phPLB(2021)·19 citations
21. 21*

    Novel correlated $D^0\overline{D}{}^0$ systems for $c/b$ physics and tests of $T/CPT$

    Paras Naik (University of Bristol, Bristol, United Kingdom)🇬🇧

    Decays of charmonia(-like) particles with definite $J^{PC}$ (e.g. ${\chi }_{c1}(3872)$) to a $D^0\overline{D}{}^0$ system and any combination of $C$-definite decay particles, are sources of quantum-correlated $D^0\overline{D}{}^0$ systems with $C=P=\pm 1$. Several $b$-hadron decays also produce quantum-correlated $D^0\overline{D}{}^0$ systems. Advantages of isolating these systems in their $C=+1$ components for amplitude analyses and studies of lineshapes are discussed. Methods to separate the $C=\pm 1$ $D^0\overline{D}{}^0$ components from ${\chi }_{c1}(3872)$ decay samples are presented. Studies of $T$ and $CPT$ conservation in $C=+1$ $D^0\overline{D}{}^0$ systems can be performed with more easily reconstructible final states, when compared to $C=-1$ $D^0\overline{D}{}^0$ systems. Experimental mechanisms that can produce $C=\pm 1$ $D^0\overline{D}{}^0$ systems are described in an appendix.

    hep-phhep-exJHEP(2023)·7 citations
22. 22*

    CP-violating inflation and its cosmological imprints

    Venus Keus🇫🇮 · Kimmo Tuominen🇫🇮

    We study models with several $SU(2)$ scalar doublets where the inert doublets have a non-minimal coupling to gravity and play the role of the inflaton. We allow for this coupling to be complex, thereby introducing CP-violation -- a necessary source of the baryon asymmetry -- in the Higgs-inflaton couplings. We investigate the inflationary dynamics of the model and discuss how the CP-violation of the model is imprinted on the particle asymmetries after inflation in the hot big bang universe.

    hep-phPRD(2021)·10 citations
23. 23*

    Dark Matter in the Type Ib Seesaw Model

    Marco Chianese🇮🇹 · Bowen Fu🇬🇧 · Stephen F. King🇬🇧

    We consider a minimal type Ib seesaw model where the effective neutrino mass operator involves two different Higgs doublets, and the two right-handed neutrinos form a heavy Dirac mass. We propose a minimal dark matter extension of this model, in which the Dirac heavy neutrino is coupled to a dark Dirac fermion and a dark complex scalar field, both charged under a discrete $Z_2$ symmetry, where the lighter of the two is a dark matter candidate. Focussing on the fermionic dark matter case, we explore the parameter space of the seesaw Yukawa couplings, the neutrino portal couplings and dark scalar to dark fermion mass ratio, where correct dark matter relic abundance can be produced by the freeze-in mechanism. By considering the mixing between between the standard model neutrinos and the heavy neutrino, we build a connection between the dark matter production and current laboratory experiments ranging from collider to lepton flavour violating experiments. For a GeV mass heavy neutrino, the parameters related to dark matter production are constrained by the experimental results directly and can be further tested by future experiments such as SHiP.

    hep-phJHEP(2021)·18 citations
24. 24*

    Solving the electron and muon $g-2$ anomalies in $Z^{\prime }$ models

    Arushi Bodas🇺🇸 · Rupert Coy🇧🇪 · Simon J.D. King🇬🇧

    We consider simultaneous explanations of the electron and muon $g-2$ anomalies through a single $Z^{\prime }$ of a $U(1{)}^{\prime }$ extension to the Standard Model (SM). We first perform a model-independent analysis of the viable flavour-dependent $Z^{\prime }$ couplings to leptons, which are subject to various strict experimental constraints. We show that only a narrow region of parameter space with an MeV-scale $Z^{\prime }$ can account for the two anomalies. Following the conclusions of this analysis, we then explore the ability of different classes of $Z^{\prime }$ models to realise these couplings, including the SM$+U(1{)}^{\prime }$, the $N$-Higgs Doublet Model$+U(1{)}^{\prime }$, and a Froggatt-Nielsen style scenario. In each case, the necessary combination of couplings cannot be obtained, owing to additional relations between the $Z^{\prime }$ couplings to charged leptons and neutrinos induced by the gauge structure, and to the stringency of neutrino scattering bounds. Hence, we conclude that no $U(1{)}^{\prime }$ extension can resolve both anomalies unless other new fields are also introduced. While most of our study assumes the Caesium $(g-2{)}_e$ measurement, our findings in fact also hold in the case of the Rubidium measurement, despite the tension between the two.

    hep-phEPJC(2021)·58 citations
25. 25*

    Four-lepton production in gluon fusion at NLO matched to parton showers

    Simone Alioli🇮🇹 · Silvia Ferrario Ravasio🇬🇧 · Jonas M. Lindert🇬🇧 · Raoul Röntsch🇨🇭

    We present a calculation of the next-to-leading order (NLO) QCD corrections to gluon-induced electroweak gauge boson pair production, $gg\to ZZ$ and $gg\to W^{+}{W}^{-}$, matched to the PYTHIA8 parton shower in the POWHEG approach. The calculation consistently incorporates the continuum background, the Higgs-mediated $gg\to H^{\ast }\to VV$ process, and their interference. We consider leptonic decay modes of the massive vector bosons and retain offshell and non-resonant contributions. The processes considered are loop-induced at leading order and thus contain two-loop virtual contributions as well as loop-squared real contributions. Parton-shower effects are found to be marginal in inclusive observables and quite sizeable in observables that are exclusive in additional jet radiation. The Monte Carlo generator presented here allows for realistic experimental effects to be incorporated in state-of-the-art precision analyses of diboson production and of the Higgs boson in the offshell regime.

    hep-phhep-exEPJC(2021)·32 citations
26. 26*

    The search for low-mass axion dark matter with ABRACADABRA-10cm

    Chiara P. Salemi🇺🇸 · Joshua W. Foster🇺🇸 · Jonathan L. Ouellet🇺🇸 · Andrew Gavin🇺🇸 · Kaliroe M. W. Pappas🇺🇸 · Sabrina Cheng🇺🇸 · Kate A. Richardson🇺🇸 · Reyco Henning🇺🇸 · Yonatan Kahn🇺🇸 · Rachel Nguyen🇺🇸 · Nicholas L. Rodd🇺🇸 · Benjamin R. Safdi🇺🇸 · Lindley Winslow🇺🇸

    Two of the most pressing questions in physics are the microscopic nature of the dark matter that comprises 84% of the mass in the universe and the absence of a neutron electric dipole moment. These questions would be resolved by the existence of a hypothetical particle known as the quantum chromodynamics (QCD) axion. In this work, we probe the hypothesis that axions constitute dark matter, using the ABRACADABRA-10cm experiment in a broadband configuration, with world-leading sensitivity. We find no significant evidence for axions, and we present 95% upper limits on the axion-photon coupling down to the world-leading level $g_{a\gamma \gamma }<3.2\times 10^{-11}$ GeV${}^{-1}$, representing one of the most sensitive searches for axions in the 0.41 - 8.27 neV mass range. Our work paves a direct path for future experiments capable of confirming or excluding the hypothesis that dark matter is a QCD axion in the mass range motivated by String Theory and Grand Unified Theories.

    ↳ hep-exhep-phPRL(2021)·216 citations
27. 27*

    Charmonium production in pp, p+Pb and Pb+Pb collisions with CMS experiment

    Abdulla Abdulsalam (on behalf of the CMS collaboration)🇸🇦

    We report the measurements of the prompt and non-prompt J/{\psi} and {\psi}(2S) nuclear modification factors (RAA) using pp and PbPb data and the RpPb using pPb data collected by CMS at the LHC. All measurements were performed via the di-muon decay channel. The RAA analysis is based on PbPb and pp data samples collected at 5.02 TeV in 2015, corresponding to integrated luminosities of 464 {\mu}b-1 and 28 pb-1. These measurements are performed in the di-muon rapidity range of |y| < 2.4 as a function of centrality, rapidity, and transverse momentum (pT) from pT = 3 GeV/c in the most forward region and up to 50 GeV/c. The RpPb analysis based on pPb data, is performed for prompt J/{\psi} and {\psi}(2S) in different kinematic bins of pT and rapidity.

    ↳ hep-exhep-phJ.Phys.Conf.Ser.(2019)·3 citations
28. 28*

    Thermodynamics of partonic matter in relativistic heavy-ion collisions from a multiphase transport model

    Han-Sheng Wang🇨🇳 · Guo-Liang Ma🇨🇳 · Zi-Wei Lin🇺🇸 · Wei-jie Fu🇨🇳

    Using the string melting version of a multiphase transport model, we focus on the evolution of thermodynamic properties of the central cell of parton matter produced in Au$+$Au collisions ranging from 200 GeV down to 2.7 GeV. The temperature and chemical potentials have been calculated based on both Boltzmann and quantum statistics in order to locate their evolution trajectories in the QCD phase diagram. We demonstrate that the trajectories can depend on many physical factors, especially the finite nuclear thickness at lower energies. However, from the evolution of pressure anisotropy, only partial thermalization can be achieved when the partonic systems reach the predicted QCD phase boundary. It provides some helpful insights to studying the QCD phase structure through relativistic heavy-ion collisions.

    ↳ nucl-thhep-phnucl-exPRC(2022)·15 citations
29. 29*

    Electron-positron vacuum instability in strong electric fields. Relativistic semiclassical approach

    D. N. Voskresensky🇷🇺

    Instability of electron-positron vacuum in strong electric fields is studied. First, falling to the Coulomb center is discussed at $Z>137/2$ for a spinless boson and at $Z>137$ for electron. Then, focus is concentrated on description of deep electron levels and spontaneous positron production in the field of a finite-size nucleus with the charge $Z>Z_{\mathrm{cr}}\simeq 170$. Next, these effects are studied in application to the low-energy heavy-ion collisions. Then, we consider phenomenon of "electron condensation" on levels of upper continuum crossed the boundary of the lower continuum $ϵ=-m$ in the field of a supercharged nucleus with $Z\gg Z_{\mathrm{cr}}$. Finally, attention is focused on many-particle problems of polarization of the QED vacuum and electron condensation at ultra-short distances from a source of charge. We argue for a principal difference of cases, when the size of the source is larger than the pole size $r_{\mathrm{pole}}$, at which the dielectric permittivity of the vacuum reaches zero, and smaller $r_{\mathrm{pole}}$. Some arguments are presented in favor of the logical consistency of QED. All problems are considered within the same relativistic semiclassical approach.

    ↳ nucl-thhep-phhep-thquant-phUniverse(2021)·19 citations
30. 30*

    Standard Model Baryon Number Violation Seeded by Black Holes

    V. De Luca🇨🇭 · G. Franciolini🇨🇭 · A. Kehagias🇬🇷 · A. Riotto🇨🇭

    We show that black holes with a Schwarzschild radius of the order of the electroweak scale may act as seeds for the baryon number violation within the Standard model via sphaleron transitions. The corresponding rate is faster than the one in the pure vacuum and baryon number violation around black holes can take place during the evolution of the universe after the electroweak phase transition. We show however that this does not pose any threat for a pre-existing baryon asymmetry in the universe.

    ↳ astro-ph.COgr-qchep-phhep-thPLB(2021)·24 citations
31. 31*

    Isovector electromagnetic form factors of the nucleon from lattice QCD and the proton radius puzzle

    D. Djukanovic🇩🇪 · T. Harris🇬🇧 · G. von Hippel🇩🇪 · P.M. Junnarkar🇩🇪 · H.B. Meyer🇩🇪 · D. Mohler🇩🇪 · K. Ottnad🇩🇪 · T. Schulz🇩🇪 · J. Wilhelm🇩🇪 · H. Wittig🇩🇪

    We present results for the isovector electromagnetic form factors of the nucleon computed on the CLS ensembles with $N_f=2+1$ flavors of $\mathcal{O}(a)$-improved Wilson fermions and an $\mathcal{O}(a)$-improved vector current. The analysis includes ensembles with four lattice spacings and pion masses ranging from 130 MeV up to 350 MeV and mainly targets the low-$Q^2$ region. In order to remove any bias from unsuppressed excited-state contributions, we investigate several source-sink separations between 1.0 fm and 1.5 fm and apply the summation method as well as explicit two-state fits. The chiral interpolation is performed by applying covariant chiral perturbation theory including vector mesons directly to our form factor data, thus avoiding an auxiliary parametrization of the $Q^2$ dependence. At the physical point, we obtain $\mu =4.71(11{)}_{\mathrm{stat}}(13{)}_{\mathrm{sys}}$ for the nucleon isovector magnetic moment, in good agreement with the experimental value and $⟨r_{\mathrm{M}}^2⟩=0.661(30{)}_{\mathrm{stat}}(11{)}_{\mathrm{sys}}{\mathrm{fm}}^2$ for the corresponding square-radius, again in good agreement with the value inferred from the $ep$-scattering determination [Bernauer et~al., Phys. Rev. Lett., 105, 242001 (2010)] of the proton radius. Our estimate for the isovector electric charge radius, $⟨r_{\mathrm{E}}^2⟩=0.800(25{)}_{\mathrm{stat}}(22{)}_{\mathrm{sys}}{\mathrm{fm}}^2$, however, is in slight tension with the larger value inferred from the aforementioned $ep$-scattering data, while being in agreement with the value derived from the 2018 CODATA average for the proton charge radius.

    ↳ hep-lathep-phnucl-thPRD(2021)·50 citations
32. 32*

    IR quantum gravity solves naturally cosmic acceleration and its coincidence problem

    Fotios K. Anagnostopoulos🇬🇷 · Georgios Kofinas🇬🇷 · Vasilios Zarikas🇰🇿

    The novel idea is that the undergoing accelerated expansion of the universe happens due to infrared quantum gravity modifications at intermediate astrophysical scales of galaxies or galaxy clusters, within the framework of Asymptotically Safe gravity. The reason is that structures of matter are associated with a scale-dependent positive cosmological constant of quantum origin. In this context, no extra unproven energy scales or fine-tuning are used. Furthermore, this model was confronted with the most recent observational data from a variety of probes, and with the aid of Bayesian analysis, the most probable values of the free parameters were extracted. Finally, the model proved to be statistically equivalent with $\Lambda$CDM, and thus being able to resolve naturally the concept of dark energy and its associated cosmic coincidence problem.

    ↳ gr-qchep-phhep-thInt.J.Mod.Phys.D(2019)·14 citations
33. 33*

    Long-Lived Particles at Future Colliders

    Rebeca Gonzalez Suarez🇸🇪

    Long-lived particles have significant enough lifetimes as to, when produced in collisions, leave a distinct signature in the detectors. Driven by increasingly higher energies, trigger and reconstruction algorithms at particle colliders are optimized for increasingly heavier particles, which in turn, tend to be short-lived. This makes searches for long-lived particles difficult, usually requiring dedicated methods and sometimes dedicated hardware top spot them. However, taking upon the challenge brings enormous potential, since new, long-lived particles feature in a variety of promising new physics models that could answer most of the open questions of the standard model, such as: neutrino masses, Dark Matter, or the matter-antimatter unbalance in the Universe. Currently, the international high energy physics community is planning future facilities post-LHC, and various particle colliders have been proposed. Crucial physics cases connected to long-lived particles will be accessible then, and in this presentation, three interesting examples are highlighted: Heavy Neutral Leptons, Hidden Sectors connected to Dark Matter, and exotic Higgs boson decays. This is followed by a small review of the preliminary studies assuming different future colliders, exploiting the complementary advantages that different colliding particles and accelerator types provide.

    ↳ hep-exhep-phActa Phys.Polon.B(2021)·6 citations
34. 34*

    Model-Independent Detection of New Physics Signals Using Interpretable Semi-Supervised Classifier Tests

    Purvasha Chakravarti🇬🇧 · Mikael Kuusela🇺🇸 · Jing Lei🇺🇸 · Larry Wasserman🇺🇸

    A central goal in experimental high energy physics is to detect new physics signals that are not explained by known physics. In this paper, we aim to search for new signals that appear as deviations from known Standard Model physics in high-dimensional particle physics data. To do this, we determine whether there is any statistically significant difference between the distribution of Standard Model background samples and the distribution of the experimental observations, which are a mixture of the background and a potential new signal. Traditionally, one also assumes access to a sample from a model for the hypothesized signal distribution. Here we instead investigate a model-independent method that does not make any assumptions about the signal and uses a semi-supervised classifier to detect the presence of the signal in the experimental data. We construct three test statistics using the classifier: an estimated likelihood ratio test (LRT) statistic, a test based on the area under the ROC curve (AUC), and a test based on the misclassification error (MCE). Additionally, we propose a method for estimating the signal strength parameter and explore active subspace methods to interpret the proposed semi-supervised classifier in order to understand the properties of the detected signal. We also propose a Score test statistic that can be used in the model-dependent setting. We investigate the performance of the methods on a simulated data set related to the search for the Higgs boson at the Large Hadron Collider at CERN. We demonstrate that the semi-supervised tests have power competitive with the classical supervised methods for a well-specified signal, but much higher power for an unexpected signal which might be entirely missed by the supervised tests.

    ↳ stat.APhep-phphysics.data-an31 citations
35. 35*

    Approach to scaling in axion string networks

    Mark Hindmarsh🇫🇮 · Joanes Lizarraga🇪🇸 · Asier Lopez-Eiguren🇺🇸 · Jon Urrestilla🇪🇸

    We study the approach to scaling in axion string networks in the radiation era, through measuring the root-mean-square velocity $v$ as well as the scaled mean string separation $x$. We find good evidence for a fixed point in the phase-space analysis in the variables $(x,v)$, providing a strong indication that standard scaling is taking place. We show that the approach to scaling can be well described by a two parameter velocity-one-scale (VOS) model, and show that the values of the parameters are insensitive to the initial state of the network. The string length has also been commonly expressed in terms of a dimensionless string length density $\zeta$, proportional to the number of Hubble lengths of string per Hubble volume. In simulations with initial conditions far from the fixed point $\zeta$ is still evolving after half a light-crossing time, which has been interpreted in the literature as a long-term logarithmic growth. We show that all our simulations, even those starting far from the fixed point, are accounted for by a VOS model with an asymptote of ${\zeta }_{\ast }=1.20\pm 0.09$ (calculated from the string length in the cosmic rest frame) and $v_{\ast }=0.609\pm 0.014$.

    ↳ astro-ph.COhep-phPRD(2021)·76 citations
36. 36*

    On dark stars, Planck cores and the nature of dark matter

    Igor Nikitin🇩🇪

    Dark stars are compact massive objects, described by Einstein gravitational field equations with matter. The type we consider possesses no event horizon, instead, there is a deep gravitational well with a very strong redshift factor. Observationally, dark stars can be identified with black holes. Inside dark stars, Planck density of matter is reached, Planck cores are formed, where the equations are modified by quantum gravity. In the paper, several models of dark stars with Planck cores are considered, resulting in the following hypothesis on the composition of dark matter. The galaxies are flooded with low-energetic radiation from the dark stars. The particle type can be photons and gravitons from the Standard Model, can also be a new type of massless particles. The model estimations show that the extremely large redshift factor $z\sim 10^{49}$ and the emission wavelength ${\lambda }_0\sim 10^{14}$m can be reached. The particles are not registered directly in the existing dark matter experiments. They come in a density sufficient to explain the observable rotation curves. The emission has a geometric dependence of density on radius $\rho \sim r^{-2}$, producing flat rotation curves. The distribution of sources also describes the deviations from the flat shape. The model provides a good fit of experimental rotation curves. Outbreaks caused by a fall of an external object on a dark star lead to emission wavelength shifted towards smaller values. The model estimations give the outbreak wavelength $\lambda \sim 1$m compatible with fast radio bursts. The paper raises several principal questions. White holes with Planck core appear to be stable. Galactic rotation curves in the considered setup do not depend on the matter type. Inside the galaxy, dark matter can be of hot radial type. At cosmological distances, it can behave like the cold uniform type.

    ↳ astro-ph.GAgr-qchep-phBled Workshops Phys.(2020)·1 citation
37. 37*

    Identification of the metric for diagonalizable (anti-)pseudo-Hermitian Hamilton operators represented by two-dimensional matrices

    Frieder Kleefeld (Collab. of CeFEMA at IST, Lisbon, Portugal)🇵🇹

    A general strategy is provided to identify the most general metric for diagonalizable pseudo-Hermitian and anti-pseudo-Hermitian Hamilton operators represented by two-dimensional matrices. It is investigated how a permutation of the eigen-values of the Hamilton operator in the process of its diagonalization influences the metric and how this permutation equivalence affects energy eigen-values. We try to understand on one hand, how the metric depends on the normalization of the chosen left and right eigen-basis of the matrix representing the diagonalizable pseudo-Hermitian or anti-pseudo-Hermitian Hamilton operator, on the other hand, whether there has to exist a positive semi-definite metric required to set up a meaningful Quantum Theory even for non-Hermitian Hamilton operators of this type. Using our general strategy we determine the metric with respect to the two elements of the two-dimensional permutation group for various topical examples of matrices representing two-dimensional Hamilton operators found in the literature assuming on one hand pseudo-Hermiticity, on the other hand anti-pseudo-Hermiticity. The (unnecessary) constraint inferred by C. M. Bender and collegues that the $\mathcal{C}$-operator of $\mathcal{P}\mathcal{T}$-symmetric Quantum Theory should be an involution (${\mathcal{C}}^2=1$) is shown - in the unbroken phase of $\mathcal{P}\mathcal{T}$-symmetry - to require the Hamilton operator to be symmetric. This inconvenient restriction had been already - with hesitation - noted by M. Znojil and H. B. Geyer in 2006 (arXiv:quant-ph/0607104). A Hamilton operator proposed by T. D. Lee and C. G. Wick is used to outline implications of the formalism to higher dimensional Hamilton operators.

    ↳ quant-phhep-phhep-thmath-ph+11 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.