Tue·Nov 3, 2020Tuesday·November 3, 2020

1. 01*

   Gravitational form factors of a baryon with spin-3/2

   June-Young Kim🇩🇪 · Bao-Dong Sun🇨🇳

   The energy-momentum tensor (EMT) for a spin-3/2 baryon is related to \emph{seven} mechanical quantities. In this work, we provide the general form of the gravitational form factors (GFFs) for a spin-3/2 baryon by using the multipole expansion and interesting relations between the EMT densities and the GFFs. To verify those general relations, we study the nucleon and the $\Delta$ GFFs within the SU(2) Skyrme model based on the large $N_c$ limit.

   hep-phEPJC(2021)·50 citations
2. 02*

   b-baryon semi-tauonic decays in the Standard Model

   Chao Han🇨🇳 · Chun Liu🇨🇳

   Within the framework of HQET, ${\Lambda }_b\to {\Lambda }_c\tau {\bar{\nu }}_{\tau }$ and ${\Omega }_b\to {\Omega }_c^{(\ast )}\tau {\bar{\nu }}_{\tau }$ weak decays are studied to the order of $1/m_c$ and $1/m_b$. Helicity amplitudes are written down. Relevant Isgur-Wise functions given by QCD sum rule and large $N_c$ methods are applied in the numerical analysis. The baryonic R-ratios $R({\Lambda }_c)$ and $R({\Omega }_c^{(\ast )})$ are obtained.

   hep-phNPB(2020)·5 citations
3. 03*

   Full heavy dibaryons

   Hongxia Huang🇨🇳 · Jialun Ping🇨🇳 · Xinmei Zhu🇨🇳 · Fan Wang🇨🇳

   The existence of full heavy dibaryons ${\Omega }_{ccc}{\Omega }_{bbb}$, ${\Omega }_{ccc}{\Omega }_{ccc}$ and ${\Omega }_{bbb}{\Omega }_{bbb}$ with $J=0,1,2,3$ and $P=\pm 1$ are investigated in the framework of a constituent quark model. The dibaryon composed of six $c$ or $b$ quarks with $J^P=0^{+}$ is possible to be bound, while the dibaryon with the $cccbbb$ configuration is difficult to form any bound state. We also study the interaction between two full heavy baryons, and the effective potentials, suggesting the existence of dibaryons ${\Omega }_{ccc}{\Omega }_{ccc}$ and ${\Omega }_{bbb}{\Omega }_{bbb}$, and the absence of binding for ${\Omega }_{ccc}{\Omega }_{bbb}$ system. Besides, the calculation of the low-energy scattering phase shifts of the ${\Omega }_{ccc}{\Omega }_{ccc}$ and ${\Omega }_{bbb}{\Omega }_{bbb}$, as well as the scattering length also confirm the existence of stable full heavy dibaryons ${\Omega }_{ccc}{\Omega }_{ccc}$ and ${\Omega }_{bbb}{\Omega }_{bbb}$.

   hep-phnucl-thEPJC(2022)·40 citations
4. 04*

   Revised QCD effects on the $Z\to b\bar{b}$ forward-backward asymmetry in $e^{+}{e}^{-}$ collisions

   David d'Enterria🇨🇭 · Cynthia Yan🇺🇸

   The forward-backward (FB) asymmetry of $b$ quarks in $e^{+}{e}^{-}$ collisions at the Z pole measured at LEP, $A_{\text{FB}}^{0,b}=0.0992\pm 0.0016$, remains today one of the electroweak precision observables with the largest disagreement (2.4$\sigma$) with respect to the Standard Model prediction, $(A_{\text{FB}}^{0,b}{)}_{{}_{\text{th}}}=0.1030\pm 0.0002$. Beyond the dominant statistical uncertainties, QCD effects, such as $b$-quark showering and hadronization, are the leading sources of $A_{\text{FB}}^{0,b}$ systematic uncertainty, and have not been revised in the last twenty years. We reassess the QCD uncertainties of the eight original $A_{\text{FB}}^{0,b}$ LEP measurements, using modern parton shower PYTHIA 8 and VINCIA simulations with nine different implementations of soft and collinear radiation as well as of parton fragmentation. Our analysis, combined with NNLO massive $b$-quark corrections independently computed, indicates total propagated QCD uncertainties of $\sim$0.7\% and $\sim$0.3\% for the lepton- and jet-charge analyses, respectively, that are about a factor of two smaller than those of the original LEP results. Accounting for such updated QCD effects leads to a new $A_{\text{FB}}^{0,b}=0.0995\pm 0.0016$ average, with a data-theory tension slightly reduced from 2.4$\sigma$ to 2.2$\sigma$. Confirmation or resolution of this long-term discrepancy requires a new high-luminosity $e^{+}{e}^{-}$ collider collecting orders-of-magnitude more data at the Z pole to significantly reduce the dominant $A_{\text{FB}}^{0,b}$ statistical uncertainties, and to improve our understanding of $b$-quark showering and hadronization.

   hep-phhep-exEPJA(2025)·27 citations
5. 05*

   Reanalysis of the top-quark pair hadroproduction and a precise determination of the top-quark pole mass at the LHC

   Sheng-Quan Wang🇨🇳 · Xing-Gang Wu🇨🇳 · Jian-Ming Shen🇨🇳 · Stanley J. Brodsky🇺🇸

   In this paper, we calculate the $t\bar{t}$ pQCD production cross-section at NNLO and determine the top-quark pole mass from recent measurements at the LHC at $\sqrt{S}=13$ TeV center-of-mass energy to high precision by applying the Principle of Maximum Conformality (PMC). The PMC provides a systematic method which rigorously eliminates QCD renormalization scale ambiguities by summing the nonconformal $\beta$ contributions into the QCD coupling constant. The PMC predictions satisfy the requirements of renormalization group invariance, including renormalization scheme independence, and the PMC scales accurately reflect the virtuality of the underlying production subprocesses. By using the PMC, an improved prediction for the $t\bar{t}$ production cross-section is obtained without scale ambiguities, which in turn provides a precise value for the top-quark pole mass. Moreover, the predictive power of PMC calculations that the magnitude of higher-order PMC predictions are well within the error bars predicted from the known lower-order has been demonstrated for the top-quark pair production. The resulting determination of the top-quark pole mass $m_t^{\mathrm{pole}}=172.5\pm 1.4$ GeV from the LHC measurement at $\sqrt{S}=13$ TeV is in agreement with the current world average cited by the Particle Data Group (PDG). The PMC prediction provides an important high-precision test of the consistency of pQCD and the SM at $\sqrt{S}=13$ TeV with previous LHC measurements at lower CM energies.

   hep-phCPC(2021)·4 citations
6. 06*

   Uncovering the Root of LEFT in SMEFT

   Joydeep Chakrabortty🇮🇳 · Suraj Prakash🇮🇳 · Shakeel Ur Rahaman🇮🇳 · Michael Spannowsky🇬🇧

   At energies below the electroweak scale, baryon number $B$ and lepton number $L$ violating processes are of significant importance in identifying the nature of UV extensions of the Standard Model. The imprint of UV theories on low-energy measurements can be calculated to a high accuracy using the theoretical framework of the Low Energy Effective Theory (LEFT). Using $B,L$ and the operators' dimensions as classifying characteristics, we construct a network connecting operator classes of the LEFT with the Standard Model Effective Theory (SMEFT). Following the links of this network, the contact interactions described by the effective operators of LEFT can be unambiguously embedded into those of SMEFT, which enables us to constrain the possible realisations of UV theories. In turn, this can help to prioritise low energy measurements with the aim of comprehensively testing all classes of LEFT and SMEFT operators.

   hep-phEPL(2021)·6 citations
7. 07*

   Two-Meson Form Factors in Unitarized Chiral Perturbation Theory

   Yu-Ji Shi🇩🇪 · Chien-Yeah Seng🇩🇪 · Feng-Kun Guo🇨🇳 · Bastian Kubis🇩🇪 · Ulf-G. Meißner🇩🇪 · Wei Wang🇨🇳

   We present a comprehensive analysis of form factors for two light pseudoscalar mesons induced by scalar, vector, and tensor quark operators. The theoretical framework is based on a combination of unitarized chiral perturbation theory and dispersion relations. The low-energy constants in chiral perturbation theory are fixed by a global fit to the available data of the two-meson scattering phase shifts. Each form factor derived from unitarized chiral perturbation theory is improved by iteratively applying a dispersion relation. This study updates the existing results in the literature and explores those that have not been systematically studied previously, in particular the two-meson tensor form factors within unitarized chiral perturbation theory. We also discuss the applications of these form factors as mandatory inputs for low-energy phenomena, such as the semi-leptonic decays $B_s\to {\pi }^{+}{\pi }^{-}{\ell }^{+}{\ell }^{-}$ and the $\tau$ lepton decay $\tau \to {\pi }^{-}{\pi }^0{\nu }_{\tau }$, in searches for physics beyond the Standard Model.

   hep-phhep-exnucl-thJHEP(2021)·20 citations
8. 08*

   Insights into the inner structures of the fully charmed tetraquark state $X(6900)$

   Zhi-Hui Guo🇨🇳 · J. A. Oller🇪🇸

   The recently discovered fully charmed tetraquark candidate $X(6900)$ is analyzed within the frameworks of effective-range expansion, compositeness relation and width saturation, and a coupled multichannel dynamical study. By taking into account constraints from heavy-quark spin symmetry, the coupled-channel amplitude including the $J/\psi J/\psi ,{\chi }_{c0}{\chi }_{c0}$ and ${\chi }_{c1}{\chi }_{c1}$ is constructed to fit the experimental di-$J/\psi$ event distributions around the energy region near $6.9$ GeV. Another dynamical two-coupled-channel amplitude with the $J/\psi J/\psi$ and $\psi (3770)J/\psi$ is also considered to describe the same datasets. The three different theoretical approaches lead to similar conclusions that the two-meson components do not play dominant roles in the $X(6900)$. Our determinations of the resonance poles in the complex energy plane from the refined coupled-channel study are found to be consistent with the experimental analyses. The coupled-channel amplitudes also have another pole corresponding to a narrow resonance $X(6825)$ that we predict sitting below the ${\chi }_{c0}{\chi }_{c0}$ threshold and of molecular origin. We give predictions to the line shapes of the ${\chi }_{c0}{\chi }_{c0}$ and ${\chi }_{c1}{\chi }_{c1}$ channels, which could provide a useful guide for future experimental measurements.

   hep-phhep-exPRD(2021)·81 citations
9. 09*

   HECATE: A long lived particle detector concept for the FCC-ee or CEPC

   Marcin Chrzaszcz🇵🇱 · Marco Drewes🇧🇪 · Jan Hajer🇧🇪

   The next generation of circular high energy collider is expected to be a lepton collider, FCC-ee at CERN or CEPC in China. However, the civil engineering concepts foresee to equip these colliders with bigger detector caverns than one would need for a lepton collider, so that they can be used for a hadron collider that may be installed in the same tunnel without further civil engineering. This opens up the possibility to install extra instrumentation at the cavern walls to search for new long-lived particles at the lepton collider. We use the example of heavy neutral leptons to show that such an installation could improve the sensitivity to the squared mixing parameter by almost half an order of magnitude.

   hep-phhep-exphysics.ins-detEPJC(2021)·48 citations
10. 10*

    NNLO QCD predictions for W+c-jet production at the LHC

    Michał Czakon🇩🇪 · Alexander Mitov🇬🇧 · Mathieu Pellen🇬🇧 · Rene Poncelet🇬🇧

    We study the production of a W boson in association with a c-jet at the LHC. We calculate, for the first time, the complete set of NNLO QCD corrections to the dominant CKM-diagonal contribution to this process. Both signatures, $\mathrm{p}\mathrm{p}\to {\mu }^{+}{\nu }_{\mu }{\mathrm{j}}_{\mathrm{c}}$ and $\mathrm{p}\mathrm{p}\to {\mu }^{-}{\bar{\nu }}_{\mu }{\mathrm{j}}_{\mathrm{c}}$ are considered. We present predictions for fiducial cross sections and differential distributions for each one of the two signatures as well as for their ratio. The theoretical predictions are compared with ATLAS measurements at $7\mathrm{TeV}$. The results of this work are essential for the precision description of associated heavy flavor production at hadron colliders and for the determination of the strange-quark content of the proton from LHC data in NNLO QCD.

    hep-phhep-exJHEP(2021)·58 citations
11. 11*

    Investigation of Effects of New Physics in $c\to (s,d){\ell }^{+}{\nu }_{\ell }$ Transitions

    Xue Leng🇨🇳 · Xiao-Long Mu🇨🇳 · Zhi-Tian Zou🇨🇳 · Ying Li🇨🇳

    Recent anomalies in decays induced by $b\to c{\ell }^{-}{\bar{\nu }}_{\ell }$ transitions raise the question about such phenomena in the $D$ decays induced by $c\to (s,d){\ell }^{+}{\nu }_{\ell }$ transitions. In the experimental side, current measurements on the pure leptonic and semileptonic $D$ decays agree with the standard model predictions, such agreements can be used to constrain the new physics (NP) contributions. In this work, we extend the standard model by assuming general effective Hamiltonians describing the $c\to (s,d){\ell }^{+}{\nu }_{\ell }$ transitions including the full set of the four-fermion operators. Within the latest experimental data, we perform a minimum ${\chi }^2$ fit of the Wilson coefficient corresponding to each operator. The results show that the Wilson coefficients of scalar operators in muon sector are at the order of $\mathcal{O}(10^{-2})$, and others are at the order of $\mathcal{O}(10^{-3})$. The lepton flavor universality could be violated by the scalar operators. We also calculate the branching fractions, the forward-backward asymmetries and polarizations of final vector mesons and leptons with the fitted Wilson coefficients of scalar and tensor operators. It is found that the pure leptonic decays are very sensitive to the scalar operators. The effects of NP on the semileptonic decays with electron are negligible, while for the semileptonic decays with muon the effects of scalar operators will show up in the forward-backward asymmetries and polarizations of muon of $D\to P{\mu }^{+}{\nu }_{\mu }$. The future measurements in BESIII and Belle II experiments will help us to test effects of NP and to further test new physics models.

    hep-phhep-exCPC(2021)·38 citations
12. 12*

    Establishing the first hidden-charm pentaquark with strangeness

    Hua-Xing Chen🇨🇳 · Wei Chen🇨🇳 · Xiang Liu🇨🇳 · Xiao-Hai Liu🇨🇳

    We study the $P_{cs}(4459{)}^0$ recently observed by LHCb using the method of QCD sum rules. Our results support its interpretation as the ${\bar{D}}^{\ast }{\Xi }_c$ hadronic molecular state of either $J^P=1/2^{-}$ or $3/2^{-}$. Within the hadronic molecular picture, the three LHCb experiments observing $P_c$ and $P_{cs}$ states \cite{lhcb,Aaij:2015tga,Aaij:2019vzc} can be well understood as a whole. This strongly supports the existence of hadronic molecules, whose studies can significantly improve our understanding on the construction of the subatomic world. To verify this picture, we propose to further investigate the $P_{cs}(4459{)}^0$ to examine whether it can be separated into two states, and to search for the $\bar{D}{\Xi }_c$ molecular state of $J^P=1/2^{-}$.

    hep-phhep-exEPJC(2021)·114 citations
13. 13*

    Lessons from the $B^{0,+}\to K^{\ast 0,+}{\mu }^{+}{\mu }^{-}$ angular analyses

    Marco Ciuchini🇮🇹 · Marco Fedele🇩🇪 · Enrico Franco🇮🇹 · Ayan Paul🇩🇪 · Luca Silvestrini🇮🇹 · Mauro Valli🇺🇸

    We perform an analysis within the Standard Model of $B^{0,+}\to K^{\ast 0,+}{\mu }^{+}{\mu }^{-}$ decays in light of the recent measurements from the LHCb experiment, showing that new data strengthen the need for sizable hadronic contributions and correlations among them. We then extend our analysis to New Physics via the Standard Model Effective Theory, and carry out a state-of-the-art fit of available $b\to s{\ell }^{+}{\ell }^{-}$ data, including possible hadronic contributions. We find the case of a fully left-handed operator standing out as the simplest scenario with a significance of almost $6\sigma$.

    hep-phhep-exPRD(2021)·118 citations
14. 14*

    Neutrino Masses and Mixing in Models with Large Extra Dimensions and Localized Fermions

    S. Girmohanta🇺🇸 · R. N. Mohapatra🇺🇸 · R. Shrock🇺🇸

    Using a low-energy effective field theory approach, we study some properties of models with large extra dimensions, in which quarks and leptons have localized wave functions in the extra dimensions. We consider models with two types of gauge groups: (i) the Standard-Model gauge group, and (ii) the left-right symmetric (LRS) gauge group. Our main focus is on the lepton sector of models with $n=2$ extra dimensions, in particular, neutrino masses and mixing. We analyze the requisite conditions that the models must satisfy to be in accord with data and present a solution for lepton wave functions in the extra dimensions that fulfills these conditions. As part of our work, we also present a new solution for quark wave function centers. Issues with flavor-changing neutral current effects are assessed. Finally, we remark on baryogenesis and dark matter in these models.

    hep-phastro-ph.COhep-thPRD(2021)·13 citations
15. 15*

    New Pathways to the Relic Abundance of Vector-Portal Dark Matter

    Patrick J. Fitzpatrick🇺🇸 · Hongwan Liu🇺🇸 · Tracy R. Slatyer🇺🇸 · Yu-Dai Tsai🇺🇸

    We fully explore the thermal freezeout histories of a vector-portal dark matter model, in the region of parameter space in which the ratio of masses of the dark photon $A^{\prime }$ and dark matter $\chi$ is in the range $1\lesssim m_{A^{\prime }}/m_{\chi }\lesssim 2$. In this region $2\to 2$ and $3\to 2$ annihilation processes within the dark sector, as well as processes that transfer energy between the dark sector and the Standard Model, play important roles in controlling the thermal freezeout of the dark matter. We carefully track the temperatures of all species, relaxing the assumption of previous studies that the dark and Standard Model sectors remain in thermal equilibrium throughout dark matter freezeout. Our calculations reveal a rich set of novel pathways which lead to the observed relic density of dark matter, and we develop a simple analytic understanding of these different regimes. The viable parameter space in our model provides a target for future experiments searching for light (MeV-GeV) dark matter, and includes regions where the dark matter self-interaction cross section is large enough to affect the small-scale structure of galaxies.

    hep-phastro-ph.COPRD(2022)·59 citations
16. 16*

    Jet quenching with $T$-dependent running coupling

    B.G. Zakharov🇷🇺

    We perform an analysis of jet quenching in heavy ion collisions at RHIC and LHC energies with the temperature dependent running QCD coupling. Our results show that the $T$-dependent QCD coupling largely eliminates the difference between the optimal values of ${\alpha }_s$ for the RHIC and LHC energies. It may be viewed as direct evidence of the increase of the thermal suppression of ${\alpha }_s$ with rising temperature.

    hep-phnucl-thJETP Lett.(2020)·5 citations
17. 17*

    Positive Moments for Scattering Amplitudes

    Brando Bellazzini🇫🇷 · Joan Elias Miró🇮🇹 · Riccardo Rattazzi🇨🇭 · Marc Riembau🇨🇭 · Francesco Riva🇨🇭

    We find the complete set of conditions satisfied by the forward $2\to 2$ scattering amplitude in unitarity and causal theories. These are based on an infinite set of energy dependent quantities -- the arcs -- which are dispersively expressed as moments of a positive measure defined at (arbitrarily) higher energies. We identify optimal finite subsets of constraints, suitable to bound Effective Field Theories (EFTs), at any finite order in the energy expansion. At tree-level arcs are in one-to-one correspondence with Wilson coefficients. We establish under which conditions this approximation applies, identifying seemingly viable EFTs where it never does. In all cases, we discuss the range of validity in both couplings and energy. We also extend our results to the case of small but finite~$t$. A consequence of our study is that EFTs in which the scattering amplitude in some regime grows in energy faster than $E^6$ cannot be UV-completed.

    ↳ hep-thhep-phPRD(2021)·272 citations
18. 18*

    Stability and pulsation of the first dark stars

    Tanja Rindler-Daller🇦🇹 · Katherine Freese🇺🇸 · Richard H.D. Townsend🇺🇸 · Luca Visinelli🇳🇱

    The first bright objects to form in the Universe might not have been "ordinary" fusion-powered stars, but "Dark Stars" (DSs) powered by the annihilation of dark matter (DM) in the form of Weakly Interacting Massive Particles (WIMPs). If discovered, DSs can provide a unique laboratory to test DM models. DSs are born with a mass of order $M_{\odot }$ and may grow to a few million solar masses; in this work we investigate the properties of early DSs with masses up to $\sim 1000M_{\odot }$, fueled by WIMPS weighing $100$ GeV. We improve the previous implementation of the DM energy source into the stellar evolution code MESA. We show that the growth of DSs is not limited by astrophysical effects: DSs up to $\sim 1000M_{\odot }$ exhibit no dynamical instabilities; DSs are not subject to mass-loss driven by super-Eddington winds. We test the assumption of previous work that the injected energy per WIMP annihilation is constant throughout the star; relaxing this assumption does not change the properties of the DSs. Furthermore, we study DS pulsations, for the first time investigating non-adiabatic pulsation modes, using the linear pulsation code GYRE. We find that acoustic modes in DSs of masses smaller than $\sim 200M_{\odot }$ are excited by the $\kappa -\gamma$ and $\gamma$ mechanism in layers where hydrogen or helium is (partially) ionized. Moreover, we show that the mass-loss rates potentially induced by pulsations are negligible compared to the accretion rates.

    ↳ astro-ph.COastro-ph.HEastro-ph.SRhep-phMNRAS(2021)·8 citations
19. 19*

    Conserved charge fluctuations in the chiral limit

    Mugdha Sarkar🇩🇪 · Olaf Kaczmarek🇩🇪 · Frithjof Karsch🇩🇪 · Anirban Lahiri🇩🇪 · Christian Schmidt🇩🇪

    We study the signs of criticality in conserved charge fluctuations and related observables of finite temperature QCD at vanishing chemical potential, as we approach the chiral limit of two light quarks. Our calculations have been performed on gauge ensembles generated using Highly Improved Staggered Quark (HISQ) fermion action, with pion masses ranging from 140 MeV to 55 MeV.

    ↳ hep-lathep-phnucl-thActa Phys.Polon.Supp.(2021)·4 citations
20. 20*

    A combined analysis of the $H_0$ late time direct measurements and the impact on the Dark Energy sector

    Eleonora Di Valentino🇬🇧

    We combine 23 Hubble constant measurements based on Cepheids-SN Ia, TRGB-SN Ia, Miras-SN Ia, Masers, Tully Fisher, Surface Brightness Fluctuations, SN II, Time-delay Lensing, Standard Sirens and $\gamma$-ray Attenuation, obtaining our best {\it optimistic} $H_0$ estimate, that is $H_0=72.94\pm 0.75$ km/s/Mpc at 68\% CL. This is in $5.9\sigma$ tension with the $\Lambda$CDM model, therefore we evaluate its impact on the extended Dark Energy cosmological models that can alleviate the tension. We find more than $4.9\sigma$ evidence for a phantom Dark Energy equation of state in the $w$CDM scenario, the cosmological constant ruled out at more than $3\sigma$ in a $w_0{w}_a$CDM model and more than $5.7\sigma$ evidence for a coupling between Dark Matter and Dark Energy in the IDE scenario. Finally, we check the robustness of our results, and we quote two additional combinations of the Hubble constant. The {\it ultra-conservative} estimate, $H_0=72.7\pm 1.1$ km/s/Mpc at 68\% CL, is obtained removing the Cepheids-SN Ia and the Time-Delay Lensing based measurements, and confirms the evidence for new physics.

    ↳ astro-ph.COgr-qchep-phhep-thMNRAS(2021)·168 citations
21. 21*

    New bosonic hard string scattering amplitudes and extended Gross conjecture in superstring theory

    Sheng-Hong Lai🇹🇼 · Jen-Chi Lee🇹🇼 · Yi Yang🇹🇼

    We discover new hard string scattering amplitudes (HSSA) with polarizations orthogonal to the scattering plane in the NS sector of 10D open superstring theory. The corresponding HSSA in the bosonic string theory are of subleading order in energy. In addition, all HSSA are found to be proportional to each other and the ratios among these HSSA are calculated to justify Gross conjecture in 1988 on high energy symmetry of string theory. Moreover, together with these new HSSA, the total number of HSSA calculated in the first massive level of NS sector are found to agree with those of hard polarized fermion string scattering amplitudes (PFSSA) in the R sector calculated recently.

    ↳ hep-thhep-phmath-phmath.MPPLB(2021)·1 citation
22. 22*

    Interacting Dark Energy in a closed universe

    Eleonora Di Valentino🇬🇧 · Alessandro Melchiorri🇮🇹 · Olga Mena🇪🇸 · Supriya Pan🇮🇳 · Weiqiang Yang🇨🇳

    Recent measurements of the Cosmic Microwave Anisotropies power spectra measured by the Planck satellite show a preference for a closed universe at more than $99\%$ Confidence Level. Such a scenario is however in disagreement with several low redshift observables, including luminosity distances of Type Ia Supernovae. Here we show that Interacting Dark Energy (IDE) models can ease the discrepancies between Planck and Supernovae Ia data in a closed Universe. Therefore IDE cosmologies remain as very appealing scenarios, as they can provide the solution to a number of observational tensions in different fiducial cosmologies. The results presented here strongly favour broader analyses of cosmological data, and suggest that relaxing the usual flatness and vacuum energy assumptions can lead to a much better agreement among theory and observations.

    ↳ astro-ph.COgr-qchep-phhep-thMNRAS(2021)·96 citations
23. 23*

    Multiplicity-dependent saturation momentum in $p$-Pb collisions at 5.02 TeV

    Takeshi Osada🇯🇵

    Semi-inclusive transverse momentum spectra observed in proton-proton and proton-lead nuclear collisions at LHC energies obey a geometric scaling with a scaling variable using multiplicity-dependent saturation momentum. The saturation momentum extracted from the experimental data is proportional to the 1/6 power of the hadron multiplicity in the final state. On the other hand, the system's transverse size is proportional to the 1/3 power of the multiplicity, and the saturation momentum and the transverse size of the system are strongly correlated with the hadron multiplicity in the final state. Since the saturation momentum is proportional to the average transverse momentum of hadrons, one predicts average transverse momentum is also proportional to the 1/6 power of the multiplicity, which is consistent with experimental results at the LHC energy. We found that a nuclear modification factor $R_{\mathrm{pPb}}$ calculated by the multiplicity-dependent saturation momentum decreases at $p_{\mathrm{T}}\lesssim$ 1GeV/$c$ and that our model can partially explain the $R_{\mathrm{pPb}}$'s behavior thought to be caused by nuclear shadowing. On the other hand, Cronin enhancement experimentally observed at $2\lesssim p_{\mathrm{T}}\lesssim$ 6 GeV/$c$ is not reproduced. However, the experimental result, including the Cronin effect, can be reproduced well by introducing $p_{\mathrm{T}}$ dependence as a 4$\sim$5\% correction to the multiplicity-dependent saturation momentum.We also discuss a relation between the geometric scaling in the semi-inclusive distributions and the string percolation model.

    ↳ nucl-thhep-phPRC(2021)·5 citations
24. 24*

    QCD in the heavy dense regime: Large $N_c$ and quarkyonic matter

    Owe Philipsen🇩🇪 · Jonas Scheunert🇩🇪

    After combined character and hopping expansions and integration over the spatial gauge links, lattice QCD reduces to a three-dimensional $SU(3)$ Polyakov loop model with complicated interactions. A simple truncation of the effective theory is valid for heavy quarks on reasonably fine lattices and can be solved by linked cluster expansion in its effective couplings. This was used ealier to demonstrate the onset transition to baryon matter in the cold and dense regime. Repeating these studies for general $N_c$, one finds that for large $N_c$ the onset transition becomes first-order, and the pressure scales as $p\sim N_c$ through three consecutive orders in the hoppoing expansion. These features are consistent with the formal definition of quarkyonic matter given in the literature. We discuss the implications for $N_c=3$ and physical QCD.

    ↳ hep-lathep-phnucl-thActa Phys.Polon.Supp.(2021)·1 citation
25. 25*

    Confinement within the use of Minkowski space integral representation

    Vladimir Sauli🇨🇿

    We determine the gluonic spectral function $SU(3)$ Yang-Mills theory as well as we found fermionic spectral functions in the strong quenched QED where we found new solutions. Our novel technique provides solutions with the usual branch cut for propagators while not showing any pole structure at the first Riemann sheet (identical with entire complex plane) of complex square of momentum. Implications and further utilizations are briefly adressed for QCD and Standard model calculations.

    ↳ hep-lathep-phhep-thPRD(2022)·10 citations
26. 26*

    Sourced fluctuations in generic slow contraction

    Michał Artymowski🇮🇱 · Ido Ben-Dayan🇮🇱 · Udaykrishna Thattarampilly🇮🇱

    We introduce a set of generic conditions for the slow contracting Universe and for a narrowed-down category of models called fast-roll models. We present general conditions for super horizon freeze-out of scalar and tensor perturbations and show that any fast-roll model satisfies them, as in the case of inflation. We are interested in the "Sourced Bounce" scenario, where perturbations are sourced by a $U(1)$ gauge field coupled to a bouncer scalar field. The requirement of a slightly red tilted scalar spectrum greatly restricts the allowed couplings between the scalar and the gauge field. We show that a viable slightly red scalar spectrum is achievable. However, within the fast-roll approximation, the tensor-to-scalar ratio is in general $r\simeq 1/9$, inconsistent with current observations. We demonstrate the general result with an explicit example we dub "Intermediate contraction". We prove that small modifications in fast-roll that do not alter the Green's functions do not result in $r<0.06$ consistent with the data for more than an e-fold. Hence, a successful "Sourced Bounce" requires a different source or a significant deviation from fast-roll.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2021)·12 citations
27. 27*

    Machine Learning Lie Structures & Applications to Physics

    Heng-Yu Chen🇹🇼 · Yang-Hui He🇬🇧 · Shailesh Lal🇵🇹 · Suvajit Majumder🇬🇧

    Classical and exceptional Lie algebras and their representations are among the most important tools in the analysis of symmetry in physical systems. In this letter we show how the computation of tensor products and branching rules of irreducible representations are machine-learnable, and can achieve relative speed-ups of orders of magnitude in comparison to the non-ML algorithms.

    ↳ hep-thcs.LGhep-phmath.RT+1PLB(2021)·21 citations
28. 28*

    Probing Geometry of Ion-Ion Collisions with Roman Pot Detectors

    Janusz J. Chwastowski🇵🇱 · Krzysztof Cieśla🇵🇱 · Rafał Staszewski🇵🇱 · Piotr Babiarz🇵🇱

    A possible use of forward proton tagging detectors at the LHC in the context of heavy ion interactions is discussed. It is shown that signals registered in such detectors are sensitive to the geometry of the collision. A method of the impact parameter and the collision asymmetry reconstruction on the event-by-event basis is proposed and its performance is studied with Monte Carlo simulations.

    ↳ hep-exhep-ph0 citations
29. 29*

    Spin-orbital magnetic response of relativistic fermions with band hybridization

    Yasufumi Araki🇯🇵 · Daiki Suenaga🇯🇵 · Kei Suzuki🇯🇵 · Shigehiro Yasui🇯🇵

    Spins of relativistic fermions are related to their orbital degrees of freedom. In order to quantify the effect of hybridization between relativistic and nonrelativistic degrees of freedom on spin-orbit coupling, we focus on the spin-orbital (SO) crossed susceptibility arising from spin-orbit coupling. The SO crossed susceptibility is defined as the response function of their spin polarization to the "orbital" magnetic field, namely the effect of magnetic field on the orbital motion of particles as the vector potential. Once relativistic and nonrelativistic fermions are hybridized, their SO crossed susceptibility gets modified at the Fermi energy around the band hybridization point, leading to spin polarization of nonrelativistic fermions as well. These effects are enhanced under a dynamical magnetic field that violates thermal equilibrium, arising from the interband process permitted by the band hybridization. Its experimental realization is discussed for Dirac electrons in solids with slight breaking of crystalline symmetry or doping, and also for quark matter including dilute heavy quarks strongly hybridized with light quarks, arising in a relativistic heavy-ion collision process.

    ↳ cond-mat.mes-hallhep-phPRResearch(2021)·9 citations
30. 30*

    Free scalar correlators in de Sitter via the stochastic approach beyond slow roll

    Archie Cable🇬🇧 · Arttu Rajantie🇬🇧

    The stochastic approach to calculating scalar correlation functions in de Sitter spacetime is extended beyond the overdamped "slow roll" approximation. We show that with the correct noise term, it reproduces the exact asymptotic long-distance behaviour of field correlators in free field theory, thereby demonstrating the viability of the technique. However, we also show that the naïve way of calculating the noise term by introducing a cut-off at the horizon does not give the correct answer unless the cut-off is chosen specifically to give the required result. We discuss the implications of this for interacting theories.

    ↳ gr-qchep-phhep-thPRD(2021)·14 citations
31. 31*

    Lattice continuum-limit study of nucleon quasi-PDFs

    Constantia Alexandrou🇨🇾 · Krzysztof Cichy🇵🇱 · Martha Constantinou🇺🇸 · Jeremy R. Green🇨🇭 · Kyriakos Hadjiyiannakou🇨🇾 · Karl Jansen🇩🇪 · Floriano Manigrasso🇨🇾 · Aurora Scapellato🇵🇱 · Fernanda Steffens🇩🇪

    The quasi-PDF approach provides a path to computing parton distribution functions (PDFs) using lattice QCD. This approach requires matrix elements of a power-divergent operator in a nucleon at high momentum and one generically expects discretization effects starting at first order in the lattice spacing $a$. Therefore, it is important to demonstrate that the continuum limit can be reliably taken and to understand the size and shape of lattice artifacts. In this work, we report a calculation of isovector unpolarized and helicity PDFs using lattice ensembles with $N_f=2+1+1$ Wilson twisted mass fermions, a pion mass of approximately 370 MeV, and three different lattice spacings. Our results show a significant dependence on $a$, and the continuum extrapolation produces a better agreement with phenomenology. The latter is particularly true for the antiquark distribution at small momentum fraction $x$, where the extrapolation changes its sign.

    ↳ hep-lathep-phnucl-thPRD(2021)·71 citations
32. 32*

    Solution to the hyperon puzzle using dark matter

    Antonino Del Popolo🇮🇹 · Maksym Deliyergiyev🇵🇱 · Morgan Le Delliou🇨🇳

    In this paper, we studied the ``hyperon puzzle", a problem that nevertheless the large number of studies is still an open problem. The solution of this issue requires one or more mechanisms that could eventually provide the additional repulsion needed to make the EoS stiffer and, therefore, the value of $M_{\max ,\mathrm{T}}$ compatible with the current observational limits. In this paper we proposed that including dark matter (DM) admixed with ordinary matter in neutron stars (NSs), change the hydrostatic equilibrium and may explain the observed discrepancies, regardless to hyperon multi-body interactions, which seem to be unavoidable. We have studied how non-self-annihilating, and self-interacting, DM admixed with ordinary matter in NSs changes their inner structure, and discussed the mass-radius relations of such NSs. We considered DM particle masses of 1, 10, and 100 GeV, while taking into account a rich list of the DM interacting strengths, $y$. By analyzing the multidimensional parameter space, including several quantities like: a. the DM interacting strength, b. the DM particle mass as well as the quantity of DM in its interior, and c. the DM fraction, ${\mathrm{f}}_{DM}$, we put constraints in the parameter space ${\mathrm{f}}_{DM}-p_{\mathrm{DM}}^{\prime }/p_{\mathrm{OM}}^{\prime }$. Our bounds are sensitive to the recently observed NSs total masses.

    ↳ gr-qcastro-ph.HEhep-phnucl-thPhys.Dark Univ.(2020)·26 citations
33. 33*

    Neutron electric dipole moment using lattice QCD simulations at the physical point

    C. Alexandrou (Univ. of Cyprus and The Cyprus Inst.)🇨🇾 · A. Athenodorou (Univ. of Pisa and The Cyprus Inst.)🇮🇹 · K. Hadjiyiannakou (Univ. of Cyprus and The Cyprus Inst.)🇨🇾 · A. Todaro (Univ. of Cyprus, Humboldt Univ. Berlin, Univ. of Rome Tor Vergata)🇨🇾

    We extract the neutron electric dipole moment $|{\vec{d}}_N|$ within the lattice QCD formalism. We analyse one ensemble of $N_f=2+1+1$ twisted mass clover-improved fermions with lattice spacing of $a\simeq 0.08\mathrm{fm}$ and physical values of the quark masses corresponding to a pion mass $m_{\pi }\simeq 139\mathrm{MeV}$. The neutron electric dipole moment is extracted by computing the $CP$-odd electromagnetic form factor $F_3(Q^2\to 0)$ through small $\theta$-expansion of the action. This approach requires the calculation of the topological charge for which we employ a fermionic definition by means of spectral projectors while we also provide a comparison with the gluonic definition accompanied by the gradient flow. We show that using the topological charge from spectral projectors leads to absolute errors that are more than two times smaller than those provided when the field theoretic definition is employed. We find a value of $|{\vec{d}}_N|=0.0009(24)\theta e\cdot \mathrm{fm}$ when using the fermionic definition, which is statistically consistent with zero.

    ↳ hep-lathep-exhep-phPRD(2021)·57 citations
34. 34*

    Spin precession as a new window into disformal scalar fields

    Philippe Brax🇫🇷 · Anne-Christine Davis🇬🇧 · Scott Melville🇬🇧 · Leong Khim Wong🇫🇷

    We launch a first investigation into how a light scalar field coupled both conformally and disformally to matter influences the evolution of spinning point-like bodies. Working directly at the level of the equations of motion, we derive novel spin-orbit and spin-spin effects accurate to leading order in a nonrelativistic and weak-field expansion. Crucially, unlike the spin-independent effects induced by the disformal coupling, which have been shown to vanish in circular binaries due to rotational symmetry, the spin-dependent effects we study here persist even in the limit of zero eccentricity, and so provide a new and qualitatively distinct way of probing these kinds of interactions. To illustrate their potential, we confront our predictions with spin-precession measurements from the Gravity Probe B experiment and find that the resulting constraint improves upon existing bounds from perihelion precession by over 5 orders of magnitude. Our results therefore establish spin effects as a promising window into the disformally coupled dark sector.

    ↳ gr-qcastro-ph.COhep-phhep-thJCAP(2021)·15 citations

* Reconstructed cohort: no mailing for this day survives in the archive. Papers are grouped by their submission times and arXiv's announcement cut-off, assuming announcement without delay; positions follow identifier order. Validated at ~91% exact-day agreement against the archived era.