Thu·Sep 22, 2022Thursday·September 22, 2022

1. 01*

   Theoretical discrepancies in the nucleon spin structure and the hyperfine splitting of muonic hydrogen

   Vladimir Pascalutsa (JGU)🇩🇪 · Franziska Hagelstein (JGU & PSI)🇩🇪 · Vadim Lensky (JGU)🇩🇪

   Two groups, ours (Mainz) and Bochum, have recently been re-evaluating the spin polarizabilities and spin structure functions at low $Q$, using the baryon chiral perturbation theory (B$\chi$PT), the manifestly-covariant counterpart of the heavy-baryon chiral perturbation theory (HB$\chi$PT). Whilst the two groups agree that the B$\chi$PT framework works better than HB$\chi$PT in this sector, their quantitative results disagree in some of the quantities; most notably, the proton spin polarizabilities ${\gamma }_0$ and ${\delta }_{LT}$. These discrepancies are especially intriguing in light of new experimental data coming from the Jefferson Lab "Spin Physics Program". The preliminary data on the proton are reported by Karl Slifer in a plenary session of this workshop. Another theoretical discrepancy is emerging in the proton-polarizability contribution to the hyperfine splitting (hfs) in hydrogen and muonic hydrogen. Our B$\chi$PT calculation shows a significantly smaller effect than the state-of-the-art data-driven evaluations based on empirical spin structure functions. The smaller polarizability contribution leads to a smaller Zemach radius of the proton. This discrepancy could be relevant for the planned first-ever measurement of the ground-state hfs in muonic hydrogen.

   hep-phnucl-exnucl-thPoS(2024)·2 citations
2. 02*

   Structure around $p\bar{p}$ threshold in $J/\psi$ radiative decays

   Qin-He Yang🇨🇳 · Di Guo🇨🇳 · Ling-Yun Dai🇨🇳

   In this paper, we study the structure around the $p\bar{p}$ threshold that appears in ${\eta }^{\prime }{\pi }^{+}{\pi }^{-}$, $3({\pi }^{+}{\pi }^{-})$ and $K_S^0{K}_S^0\eta$ invariant mass spectra in the processes of relevant $J/\psi$ radiative decays. The $N\bar{N}$ rescattering is taken into account, and the distorted-wave Born approximation is applied to get the decaying amplitude through a two-step process: $J/\psi \to \gamma N\bar{N}\to \gamma {\eta }^{\prime }{\pi }^{+}{\pi }^{-}$, $\gamma 3({\pi }^{+}{\pi }^{-})$ and $\gamma K_S^0{K}_S^0\eta$. The $N\bar{N}$ scattering amplitudes are obtained by solving the Lippmann-Schwinger equation with the potentials given by chiral effective field theory. To fix the unknown couplings, we fit the amplitudes to the datasets of the latest measurements on the invariant mass spectra of $J/\psi$ radiative decays, as well as the phase shifts and inelasticities given by partial wave analysis. We vary the cutoffs ($R$=0.9, 1.0, and 1.1 fm) and find that the solutions are stable. The structures around $p\bar{p}$ threshold found in the processes of $J/\psi \to \gamma {\eta }^{\prime }{\pi }^{+}{\pi }^{-}$, $J/\psi \to \gamma 3({\pi }^{+}{\pi }^{-})$ and $J/\psi \to \gamma K_S^0{K}_S^0\eta$ can be attributed to threshold behavior of $N\bar{N}$ intermediate states.

   hep-phPRD(2023)·13 citations
3. 03*

   Do near-threshold molecular states mix with neighbouring $\bar{Q}Q$ states?

   Christoph Hanhart🇩🇪 · Alexey Nefediev🇸🇮

   The last two decades are marked by a renaissance in hadronic spectroscopy caused by the arrival of vast experimental information on exotic states in the spectrum of charmonium and bottomonium. Most of such states have properties at odds with the predictions of the quark model and reside very close to strong hadronic thresholds. Prominent examples are provided by the glorious $X(3872)$ charmonium-like state and the doubly charmed tetraquark $T_{cc}^{+}$ with the masses within less than 1 MeV from the $D{\bar{D}}^{\ast }$ and $D{D}^{\ast }$ open-charm thresholds, respectively. The universality of this feature hints towards the existence of a general pattern for such exotic states. In this work we discuss a possible generic mechanism for the formation of near-threshold molecular states as a result of the strong coupling of compact quark states with a hadronic continuum channel. The compact states that survive the strong coupling limit decouple from the continuum channel and therefore also from the formed hadronic molecule - if realised this scenario would provide a justification to treat hadronic molecules isolated, ignoring the possible influence from surrounding, compact quark-model states. We confront the phenomenology of the $D_{s1}(2460)$ and $D_{s1}(2536)$ with this picture and find consistency, although other explanations remain possible for those states.

   hep-phhep-exhep-latPRD(2022)·20 citations
4. 04*

   Non-SUSY Lepton Flavor Model with 3HDM

   Yukimura Izawa🇯🇵 · Yusuke Shimizu🇯🇵 · Hironori Takei🇯🇵

   We propose a simple non-supersymmetric lepton flavor model with $A_4$ symmetry. The $A_4$ group is a minimal one which includes triplet irreducible representation. We introduce three Higgs doublets which are assigned as triplet of the $A_4$ symmetry. It is natural that there are three generations of the Higgs fields as same as the standard model fermions. We study the potential analysis and we get the vacuum expectation values for the local minimum. In the vacuum expectation values, we obtain the charged lepton, Dirac neutrino, and right-handed Majorana neutrino mass matrices. By using type-I seesaw mechanism, we get the left-handed Majorana neutrino mass matrix. In the NuFIT 5.1 data, we predict the Dirac CP phase and the Majorana phases for the only inverted neutrino mass hierarchy. Especially, the Dirac CP phase and lepton mixing angle ${\theta }_{23}$ are strongly correlated. If the ${\theta }_{23}$ is more precise measured, the Dirac CP phase is more precise predicted, and vice versa. We also predict the effective mass for neutrino-less double beta decay $m_{ee}\simeq 47.1[\mathrm{meV}]$ and the lightest neutrino mass $m_3\simeq 0.789$~-~$1.43[\mathrm{meV}]$. It is testable for our model in the near future neutrino experiments.

   hep-phhep-exPTEP(2023)·2 citations
5. 05*

   Probing non-unitarity of neutrino mixing in the scenario of Lorentz violation and dark nonstandard interaction

   Trisha Sarkar🇮🇳

   Neutrino flavour oscillation is one of the primary indication of the existence of new physics beyond standard model. The presence of small neutrino mass is indispensable to explicate the oscillation among different flavours of neutrino. By the addition of a right handed neutral lepton with the standard model fermions, it is possible to generate tiny neutrino mass. Such additional fermion may induce non-unitarity to the $3\times 3$ PMNS mixing matrix which influences the propagation of neutrino in space-time. In this work the effect of non-unitary mixing matrix is analyzed in neutrino oscillation in presence of two new physics scenarios, Lorentz violation and dark non-standard interaction. Lorentz symmetry violation mainly appears at the Planck scale, which may also be manifested at a lower energy level. On the other hand, dark non standard interaction arises due to the interaction of neutrino with the environmental dark matter which contributes as a perturbative correction to the neutrino mass. In this analysis, the comparative study of unitary and non-unitary mixing matrix is carried out considering the scenario of Lorentz violation and dark NSI in the context of long baseline DUNE and short baseline Daya Bay experimental set up. The signature of dark nonstandard interaction is observable in both DUNE and Daya Bay set up in terms of large value of neutrino survival and oscillation probability respectively and is a possible explanation for the excess flux observed at $\sim 5$ MeV in Daya Bay experiment. The signature of Lorentz violation is also possible to be observed in the short baseline Daya Bay experiment only.

   hep-ph9 citations
6. 06*

   Neutrino Frontier Topical Group Report (NF03): Physics Beyond the Standard Model

   Pilar Coloma🇪🇸 · Lisa W. Koerner🇺🇸 · Ian M. Shoemaker🇺🇸 · Jaehoon Yu🇺🇸

   This topical group focuses on searches for signals from physics Beyond the Standard Model (BSM), both from a theoretical and experimental perspective, including neutrino-related BSM and searches for BSM in other sectors using neutrino facilities.

   hep-phhep-ex15 citations
7. 07*

   Rich structure of the hidden-charm pentaquarks near threshold regions

   Alessandro Giachino🇵🇱 · Atsushi Hosaka🇯🇵 · Elena Santopinto🇮🇹 · Sachiko Takeuchi🇯🇵 · Makoto Takizawa🇯🇵 · Yasuhiro Yamaguchi🇯🇵

   The recent abundant observations of pentaquarks and tetraquarks by high-energy accelerator facilities indicate the realization of the conjecture by Gell-Mann and Zweig, and by De Rujula, Georgi and Glashow [1-3]. We construct a coupled-channel model for the hidden-charm pentaquarks with strangeness whose quark content is $udsc\bar{c}$, $P_{cs}$, described as ${\Lambda }_c{\bar{D}}_s^{(\ast )},{\Xi }_c^{{(}^{\prime }\ast )}{\bar{D}}^{(\ast )}$ molecules coupled to the five-quark states. These molecules are formed by the suitable cooperation of heavy quark and chiral symmetries. We reproduce the experimental mass and quantum numbers $J^P$ of $P_{cs}(4338)$ for which LHCb has just announced the discovery. We make other predictions for new $P_{cs}$ states as molecular states near threshold regions that can be studied by LHCb.

   hep-phPRD(2023)·30 citations
8. 08*

   Unified Balance Functions

   Claude Pruneau🇺🇸 · Victor Gonzales · Brian Hanley🇺🇸 · Ana Marin🇩🇪 · Sumit Basu🇸🇪

   The use of charge balance functions in heavy-ion collision studies was initially proposed as a probe of delayed hadronization and two-stage quark production in these collisions. It later emerged that general balance functions can also serve as a probe of the diffusivity of light quarks as well as the evolution of the systems formed in heavy-ion collisions. In this work, we reexamine the formulation of general balance functions and consider how to best define and measure these correlation functions in terms of differences of conditional densities of unlike-sign and like-sign particle pairs. We define general balance functions in terms of associated particle functions and show these obey a simple sum rule. We additionally proceed to distinguish between balance functions expressed as differences of conditional densities valid irrespective of experimental acceptance boundaries and bound balance functions that explicitly account for the limited acceptance of experiments. General balance functions are additionally extended to accommodate strange, baryon, as well as charm and bottom quantum numbers based on the densities of these quantum numbers.

   hep-phnucl-exnucl-thPRC(2023)·16 citations
9. 09*

   Doubly charmed dibaryon states

   Zhe Liu🇨🇳 · Hong-Tao An🇨🇳 · Zhan-Wei Liu🇨🇳 · Xiang Liu🇨🇳

   In this work, we study the doubly charmed dibaryon states with the $qqqqcc$ ($q=u,d,s$) configuration. The mass spectra of doubly charmed dibaryon states are obtained systematically within the chromomagnetic interaction model. In addition to the mass spectrum analysis, we illustrate their two-body strong decay behaviours. Our results suggest that there may be narrow states or even stable states that cannot decay through the strong interaction. We hope that our results will provide valuable information for further experimental searches for doubly charmed dibaryon states.

   hep-phhep-exCPC(2023)·11 citations
10. 10*

    Far-off-equilibrium expansion trajectories in the QCD phase diagram

    Chandrodoy Chattopadhyay (North Carolina State University)🇺🇸 · Ulrich Heinz (Ohio State University)🇺🇸 · Thomas Schaefer (North Carolina State University)🇺🇸

    We consider the hydrodynamic evolution of a quark-gluon gas with non-zero quark masses and net baryon number in its phase diagram. For far-off-equilibrium initial conditions the expansion trajectories appear to violate simple rules based on the second law of thermodynamics that were previously established for ideal or weakly dissipative fluids. For Bjorken flow we present a detailed analysis within kinetic theory that provides a full microscopic understanding of these macroscopic phenomena and establishes their thermodynamic consistency. We point out that, for certain far-off-equilibrium initial conditions, the well-known phenomenon of "viscous heating" turns into "viscous cooling" where, driven by dissipative effects, the temperature decreases faster than in adiabatic expansion.

    hep-phnucl-thPRC(2023)·17 citations
11. 11*

    Conformal Freeze-In, Composite Dark Photon, and Asymmetric Reheating

    Wen Han Chiu🇺🇸 · Sungwoo Hong🇺🇸 · Lian-Tao Wang🇺🇸

    Large classes of dark sector models feature mass scales and couplings very different from the ones we observe in the Standard Model (SM). Moreover, in the freeze-in mechanism, often employed by the dark sector models, it is also required that the dark sector cannot be populated during the reheating process like the SM. This is the so called asymmetric reheating. Such disparities in sizes and scales often call for dynamical explanations. In this paper, we explore a scenario in which slow evolving conformal field theories (CFTs) offer such an explanation. Building on the recent work on conformal freeze-in (COFI), we focus on a coupling between the Standard Model Hypercharge gauge boson and an anti-symmetric tensor operator in the dark CFT. We present a scenario which dynamically realizes the asymmetric reheating and COFI production. With a detailed study of dark matter production, and taking into account limits on the dark matter (DM) self-interaction, warm DM bound, and constraints from the stellar evolution, we demonstrate that the correct relic abundance can be obtained with reasonable choices of parameters. The model predicts the existence of a dark photon as an emergent composite particle, with a small kinetic mixing also determined by the CFT dynamics, which correlates it with the generation of the mass scale of the dark sector. At the same time, COFI production of dark matter is very different from those freeze-in mediated by the dark photon. This is an example of the physics in which a realistic dark sector model can often be much richer and with unexpected features.

    hep-phJHEP(2023)·13 citations
12. 12*

    Thermal effects in Ising Cosmology

    Nikos Irges (NTU of Athens)🇬🇷 · Antonis Kalogirou (NTU of Athens)🇬🇷 · Fotis Koutroulis (Warsaw U.)🇵🇱

    We consider a real scalar field in de Sitter background and compute its thermal propagators. We propose that in a dS/CFT context, non-trivial thermal effects as seen by an 'out' observer can be encoded in the anomalous dimensions of the $d=3$ Ising model. One of these anomalous dimensions, the critical exponent $\eta$, fixes completely a number of cosmological observables, which we compute

    ↳ hep-thgr-qchep-phUniverse(2023)·5 citations
13. 13*

    Ising Cosmology

    Nikos Irges (NTU of Athens)🇬🇷 · Antonis Kalogirou (NTU of Athens)🇬🇷 · Fotis Koutroulis (Warsaw Un.)🇵🇱

    Using arguments from holography we propose that the deviation of the cosmological spectral index $n_S$ of scalar fluctuations from unity may be controlled almost entirely by the critical exponent $\eta$ of the $d=3$ Ising model

    ↳ hep-thgr-qchep-phEPJC(2023)·4 citations
14. 14*

    Pion-mediated Cooper pairing of neutrons: beyond the bare vertex approximation

    Hao-Fu Zhu🇨🇳 · Guo-Zhu Liu🇨🇳

    In some quantum many particle systems, the fermions could form Cooper pairs by exchanging intermediate bosons. This then drives a superconducting phase transition or a superfluid transition. Such transitions should be theoretically investigated by using proper non-perturbative methods. Here we take the neutron superfluid transition as an example and study the Cooper pairing of neutrons mediated by neutral $\pi$-mesons in the low density region of a neutron matter. We perform a non-perturbative analysis of the neutron-meson coupling and compute the pairing gap $\Delta$, the critical density ${\rho }_c$, and the critical temperature $T_c$ by solving the Dyson-Schwinger equation of the neutron propagator. We first carry out calculations under the widely used bare vertex approximation and then incorporate the contribution of the lowest-order vertex correction. This vertex correction is not negligible even at low densities and its importance is further enhanced as the density increases. The transition critical line on density-temperature plane obtained under the bare vertex approximation is substantially changed after including the vertex correction. These results indicate that the vertex corrections play a significant role and need to be seriously taken into account.

    ↳ nucl-thcond-mat.supr-conhep-phJ.Phys.G(2023)·0 citations
15. 15*

    Chiral spin symmetry and hot/dense QCD

    L. Ya. Glozman🇦🇹

    Above the chiral symmetry restoration crossover around T_{ch} ~ 155 MeV a new regime arises in QCD, a stringy fluid, which is characterized by an approximate chiral spin symmetry of the thermal partition function. This symmetry is not a symmetry of the Dirac Lagrangian and is a symmetry of the electric part of the QCD Lagrangian. In this regime the medium consists of the chirally symmetric and approximately chiral spin symmetric hadrons that are made of the chirally symmetric quarks connected into the color singlet compounds by a confining chromoelectric field. This regime is evidenced by the approximate chiral spin symmetry of the spatial and temporal correlators and by the breakdown of the thermal perturbation theory at the crossover between the partonic (the quark-gluon plasma) and stringy fluid regimes at ~ 3 T_{ch}. The chiral spin symmetry smoothly disappears above ~ 3T_{ch} which means that the chromoelectric confining interaction gets screened. A direct evidence that the stringy fluid medium consists of densely packed hadrons is the pion spectral function that shows a distinct pion state and its first radial excitation above T_{ch}. Another direct evidence of the hadron degrees of freedom in the stringy fluid is the bottomonium spectrum with the 1S,2S,3S and 1P,2P radial and orbital excitations that become broad with temperature. The hadrons between T_{ch} and ~ 3 T_{ch} in the stringy fluid interact strongly which makes the stringy fluid more a liquid rather than a gas. We discuss how this chiral spin symmetric regime extends into the finite chemical potentials domain and present a qualitative sketch of the QCD phase diagram.

    ↳ hep-lathep-phhep-thnucl-ex+1PPNP(2023)·35 citations
16. 16*

    Impact of Rastall gravity on mass, radius and sound speed of the pulsar PSR J0740+6620

    Waleed El Hanafy🇪🇬

    Millisecond pulsars are perfect laboratories to test possible matter-geometry coupling and its physical implications in light of recent Neutron Star Interior Composition Explorer (NICER) observations. We apply Rastall field equations of gravity, where matter and geometry are nonminimally coupled, to Krori-Barua interior spacetime whereas the matter source is assumed to be anisotropic fluid. We show that all physical quantities inside the star can be expressed in terms of Rastall, $ϵ$, and compactness, $C=2GM/R{c}^2$, parameters. Using NICER and X-ray Multi-Mirror X-ray observational constraints on the mass and radius of the pulsar PSR J0740+6620 we determine Rastall parameter to be at most $ϵ=0.041$ in the positive range. The obtained solution provides a stable compact object; in addition the squared sound speed does not violate the conjectured sound speed $c_s^2\le c^2/3$ unlike the general relativistic treatment. We note that no equations of state are assumed; the model however fits well with linear patterns with bag constants. In general, for $ϵ>0$, the theory predicts a slightly larger size star in comparison to general relativity for the same mass. This has been explained as an additional force, due to matter-geometry coupling, in the hydrodynamic equilibrium equation, which contributes to partially diminish the gravitational force effect. Consequently, we calculate the maximal compactness as allowed by the strong energy condition to be $C=0.735$ which is $\sim 2\%$ higher than general relativity prediction. Moreover, for the surface density at saturation nuclear density ${\rho }_{\text{nuc}}=2.7\times 10^{14}$ g/cm${}^3$ we estimate the maximum mass $M=4M_{\odot }$ at radius $R=16$ km.

    ↳ astro-ph.HEgr-qchep-phApJ(2022)·42 citations
17. 17*

    Cumulants of net-strangeness multiplicity distributions at energies available at the BNL Relativistic Heavy Ion Collider

    Changfeng Li🇨🇳 · Deeptak Biswas🇮🇳 · Nihar Ranjan Sahoo🇨🇳

    The higher-order cumulants of net-proton number, net-charge, and net-strangeness multiplicity distributions are widely studied to search for the quantum-chromodynamics critical point and extract the chemical freeze-out parameters in heavy-ion collisions. In this context, the event-by-event fluctuations of the net-strangeness multiplicity distributions play important roles in extracting the chemical freeze-out parameter in the strangeness sector. Due to having difficulties in detecting all strange hadrons event by event, the kaon ($K$) and lambda ($\Lambda$) particles serve as a proxy for the strangeness-related observables in heavy-ion collisions. We have studied the net-$K$, net-$\Lambda$, and net-($K$ + $\Lambda$) multiplicity distributions and calculated their different order of cumulants using the ultrarelativistic quantum molecular dynamics model and hadron resonance gas calculation. To adequately account for the net-strangeness cumulants, it has been found that the inclusion of resonance decay contributions in $K$ and $\Lambda$ is necessary.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2023)·1 citation
18. 18*

    Exact results for the Boltzmann collision operator in $\lambda {\varphi }^4$ theory

    Gabriel S. Denicol (Niteroi, Fluminense U.)🇧🇷 · Jorge Noronha (Illinois U., Urbana)🇺🇸

    We analytically determine all the eigenvalues and eigenfunctions of the linearized Boltzmann collision operator in massless scalar $\lambda {\varphi }^4$ theory in the high-temperature (classical) regime. This is used to exactly compute the shear viscosity and particle diffusion transport coefficients of this system. The corresponding relaxation time approximation for this linearized Boltzmann equation is also derived.

    ↳ nucl-thhep-phhep-thPLB(2024)·34 citations
19. 19*

    Asymptotically Safe Hilbert-Palatini Gravity in an On-Shell Reduction Scheme

    Holger Gies🇩🇪 · Abdol Sabor Salek🇩🇪

    We study the renormalization flow of Hilbert-Palatini gravity to lowest non-trivial order. We find evidence for an asymptotically safe high-energy completion based on the existence of an ultraviolet fixed point similar to the Reuter fixed point of quantum Einstein gravity. In order to manage the quantization of the large number of independent degrees of freedom in terms of the metric as well as the connection, we use an on-shell reduction scheme: for this, we quantize all degrees of freedom beyond Einstein gravity at a given order that remain after using the equations of motion at the preceding order. In this way, we can straightforwardly keep track of the differences emerging from quantizing Hilbert-Palatini gravity in comparison with Einstein gravity. To lowest non-trivial order, the difference is parametrized by fluctuations of an additional abelian gauge field. The critical properties of the ultraviolet fixed point of Hilbert-Palatini gravity are similar to those of the Reuter fixed point, occurring at a smaller Newton coupling and exhibiting more stable higher order exponents.

    ↳ hep-thgr-qchep-phEPJC(2023)·14 citations
20. 20*

    Stability studies of first order spin-hydrodynamic frameworks

    Asaad Daher🇵🇱 · Arpan Das🇵🇱 · Radoslaw Ryblewski🇵🇱

    We study the stability of first-order dissipative spin-hydrodynamic frameworks. We considered two different first-order dissipative spin-hydrodynamic frameworks. The first one considers the spin chemical potential (${\omega }^{\alpha \beta }$) to be first order ($\mathcal{O}(\partial )$) in the hydrodynamic gradient expansion. The hydrodynamic gradient ordering of the spin chemical potential is a debatable issue within the frameworks of spin hydrodynamics. Therefore as a second choice, we also consider the spin hydrodynamic equations with ${\omega }^{\alpha \beta }\sim \mathcal{O}(1)$. We find that for both frameworks, at the level of linear perturbations some spin modes can be unstable. To remove these generic instabilities we consider the Frenkel condition. We argue that Frenkel condition helps get rid of the unstable solutions in both cases, but with a physical drawback for the case where ${\omega }^{\mu \nu }\sim \mathcal{O}(\partial )$.

    ↳ nucl-thhep-phPRD(2023)·48 citations
21. 21*

    Cross effects in spin hydrodynamics: A revisit Entropy analysis and statistical operator

    Jin Hu🇨🇳

    We revisit the construction of first-order spin hydrodynamics and find that the constitution relations receive the corrections from the cross effects resulting from spin-orbit coupling. Starting from a routine entropy analysis, we show how to identify cross effects and new cross transport coefficients from the second law of thermodynamics. Interestingly, the conventional transport coefficient heat conductivity $\kappa$ is bounded from below by the product of cross transport coefficients, which means the threshold of heat conduction is changed. With recourse to Zubarev's non-equilibrium statistical operator, we reproduce the construction of first-order spin hydrodynamics and identification of cross effects in a more rigorous way. By seeking the dispersion relations of normal modes, we find that these cross effects suppress the attenuation of sound modes and heat mode appearing in conventional hydrodynamics and also have impacts on the damping of non-hydrodynamic spin modes.

    ↳ nucl-thhep-phPRC(2023)·23 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.