Mon·Jan 18, 2021Monday·January 18, 2021

1. 01*

   Chiral kinetic theory with small mass corrections and quantum coherent states

   Cristina Manuel🇪🇸 · Juan M. Torres-Rincon🇩🇪

   We study the effect of a small fermion mass in the formulation of the on-shell effective field theory (OSEFT). This is our starting point to derive small mass corrections to the chiral kinetic theory. In the massless case, only four Wigner functions are needed to describe positive and negative energy fermions of left and right chirality, corresponding to the vectorial components of a fermionic two-point Green's function. As soon as mass correction are introduced, tensorial components are also needed, while the scalar components strictly vanish in the OSEFT. The tensorial components are conveniently parametrized in the so-called spin coherence function, which describe quantum coherent mixtures of left-right and right-left chiral fermions, of either positive or negative energy. We show that, up to second order in the energy expansion, vectorial and tensorial components are decoupled, and obey the same dispersion law and transport equation, depending on their respective chirality. We study the mass modifications of the reparametrization invariance of the OSEFT, and check that vector and tensorial components are related by the associated symmetry transformations. We study how the macroscopic properties of the system are described in terms of the whole set of Wigner functions, and check that our framework allows to account for the mass modifications to the chiral anomaly equation.

   hep-phhep-thPRD(2021)·15 citations
2. 02*

   Hyper-order baryon number fluctuations at finite temperature and density

   Wei-jie Fu🇨🇳 · Xiaofeng Luo🇨🇳 · Jan M. Pawlowski🇩🇪 · Fabian Rennecke🇺🇸 · Rui Wen🇨🇳 · Shi Yin🇨🇳

   Fluctuations of conserved charges are sensitive to the QCD phase transition and a possible critical endpoint in the phase diagram at finite density. In this work, we compute the baryon number fluctuations up to tenth order at finite temperature and density. This is done in a QCD-assisted effective theory that accurately captures the quantum- and in-medium effects of QCD at low energies. A direct computation at finite density allows us to assess the applicability of expansions around vanishing density. By using different freeze-out scenarios in heavy-ion collisions, we translate these results into baryon number fluctuations as a function of collision energy. We show that a non-monotonic energy dependence of baryon number fluctuations can arise in the non-critical crossover region of the phase diagram. Our results compare well with recent experimental measurements of the kurtosis and the sixth-order cumulant of the net-proton distribution from the STAR collaboration. They indicate that the experimentally observed non-monotonic energy dependence of fourth-order net-proton fluctuations is highly non-trivial. It could be an experimental signature of an increasingly sharp chiral crossover and may indicate a QCD critical point. The physics implications and necessary upgrades of our analysis are discussed in detail.

   hep-phnucl-exnucl-thPRD(2021)·130 citations
3. 03*

   Structure Of Flavor Changing Goldstone Boson Interactions

   Jin Sun🇨🇳 · Yu Cheng🇨🇳 · Xiao-Gang He🇹🇼

   General flavor changing interactions for a Goldstone boson (GB) to fermions due to a spontaneous global $U(1{)}_G$ symmetry breaking are discussed. This GB may be the Axion, solving the strong QCD CP problem, if there is a QCD anomaly for the $U(1{)}_G$ charge assignments for quarks. Or it may be the Majoron in models from lepton number violation in producing seesaw Majorana neutrino masses if the symmetry breaking scale is much higher than the electroweak scale. It may also, in principle, play the roles of Axion and Majoron simultaneously as far as providing solution for the strong CP problem and generating a small Majorana neutrino masses are concerned. Great attentions have been focused on flavor conserving GB interactions. Recently flavor changing Axion and Majoron models have been studied in the hope to find new physics from rare decays in the intensity frontier. In this work, we will provide a systematic model building aspect study for a GB having flavor changing neutral current (FCNC) interactions in both the quark and lepton sectors, or separately in the quark, charged lepton and neutrino sectors with sources of FCNC interactions identified in detail. We provide a general proof of the equivalence of using physical GB components and GB broken generators for calculating GB couplings to two gluons and two photons, and some issues related to models having spontaneous CP violation are discussed. We will also provide some details for obtaining FCNC GB interactions in several popular models, such as the Type-I, -II, -III seesaw and Left-Right symmetric models, and point out some special features in these models.

   hep-phJHEP(2021)·10 citations
4. 04*

   Framing energetic top-quark pair production at the LHC

   Fabrizio Caola🇬🇧 · Frédéric A. Dreyer🇬🇧 · Ross W. McDonald🇬🇧 · Gavin P. Salam🇬🇧

   Top-quark pair production is central to many facets of LHC physics. At leading order, the top and anti-top are produced in a back-to-back topology, however this topology accounts only for a minority of $t\bar{t}$ events with TeV-scale momentum transfer. The remaining events instead involve the splitting of an initial or final-state gluon to $t\bar{t}$. We provide simple quantitative arguments that explain why this is the case and examine the interplay between different topologies and a range of variables that characterise the event hardness. We then develop a method to classify the topologies of individual events and use it to illustrate our findings in the context of simulated events, using both top partons and suitably defined fiducial tops. For events with large $t\bar{t}$ invariant mass, we comment on additional features that have important experimental and theoretical implications.

   hep-phhep-exJHEP(2021)·7 citations
5. 05*

   Exploring the sensitivity of hadron colliders to non-universality in heavy neutral currents

   F. Conventi🇮🇹 · G. D'Ambrosio🇮🇹 · A.M. Iyer🇫🇷 · E. Rossi🇮🇹

   We present sensitivity projections for discovering a heavy resonance decaying to electron and muon pairs and for probing the charged lepton non-universality in such decays at the HL-LHC and FCC-hh. The analysis takes into account the expected differences in the reconstruction efficiencies and the dilepton mass resolutions for dielectron and dimuon final states. We demonstrate how the analyses at HL-LHC naturally paves the way for a FCC-hh machine thereby underlining its importance.

   hep-phhep-exInt.J.Mod.Phys.A(2022)·0 citations
6. 06*

   Electron-Ion Collider impact study on the tensor charge of the nucleon

   Leonard Gamberg🇺🇸 · Zhong-Bo Kang🇺🇸 · Daniel Pitonyak🇺🇸 · Alexei Prokudin🇺🇸 · Nobuo Sato🇺🇸 · Ralf Seidl🇺🇸

   In this letter we study the impact of the Electron-Ion Collider (EIC) on the phenomenological extraction of the tensor charge from a QCD global analysis of single transverse-spin asymmetries (SSAs). We generate EIC pseudo-data for the Collins effect in semi-inclusive deep-inelastic scattering for proton and ${}^{3}He$ beams across multiple center-of-mass energies. We find a significant reduction in the uncertainties for the up, down, and isovector tensor charges that will make their extraction from EIC data on SSAs as precise as current lattice QCD calculations. We also analyze the constraints placed by future data from the proposed SoLID experiment at Jefferson Lab, discuss its important complementary role to the EIC, and present the combined impact from both facilities.

   hep-phhep-exnucl-thPLB(2021)·18 citations
7. 07*

   Heavy quarkonia spectroscopy at zero and finite temperature in bottom-up AdS/QCD

   Miguel Angel Martin Contreras🇨🇱 · Saulo Diles🇧🇷 · Alfredo Vega🇨🇱

   S-wave states of charmonium and bottomonium are described using bottom-up AdS/QCD. We propose a holographic model that unifies the description of masses and decay constants, leading to a precise match with experimental data on heavy quarkonia. Finite temperature effects are considered by calculating the current-current spectral functions of heavy vector mesons. The identification of quasi-particle states as Breit-Wigner resonances in the holographic spectral function was made. We develop a prescription to subtract background contributions from the spectral function to isolate the Breit-Wigner peak. The quasi-particle holographic thermal evolution is described, allowing us to estimate the melting temperature for vector charmonia and bottomonia. Our holographic model predicts that $J/\Psi$ melts at $415$ MeV $(\sim 2.92T_c)$ and ${\rm Y}$ melts at $465$ MeV $(\sim 3.27T_c)$)

   hep-phPRD(2021)·38 citations
8. 08*

   The anomalous $Zb\bar{b}$ couplings: From LEP to LHC

   Bin Yan🇺🇸 · C.-P. Yuan🇺🇸

   The bottom quark forward-backward asymmetry ($A_{FB}^b$) data at LEP exhibits a long-standing discrepancy with the standard model prediction. We propose a novel method to probe the $Zb\bar{b}$ interactions through $gg\to Zh$ production at the LHC, which is sensitive to the axial-vector component of the $Zb\bar{b}$ couplings. We demonstrate that the $Zh$ data collected at the 13 TeV LHC can already resolve the apparent degeneracy of the anomalous $Zb\bar{b}$ couplings implied by the LEP precision electroweak measurements, with a strong dependence on the observed distribution of the $Z$ boson transverse momentum. We also show the potential of the HL-LHC to either verify or exclude the anomalous $Zb\bar{b}$ couplings observed at LEP through measuring the $Zh$ production rate at the HL-LHC, and this conclusion is not sensitive to possible new physics contribution induced by top quark or Higgs boson anomalous couplings in the loop.

   hep-phhep-exPRL(2021)·27 citations
9. 09*

   TwInflation

   Kaustubh Deshpande🇺🇸 · Soubhik Kumar🇺🇸 · Raman Sundrum🇺🇸

   The general structure of Hybrid Inflation remains a very well-motivated mechanism for lower-scale cosmic inflation in the face of improving constraints on the tensor-to-scalar ratio. However, as originally modeled, the "waterfall" field in this mechanism gives rise to a hierarchy problem ($\eta -$problem) for the inflaton after demanding standard effective field theory (EFT) control. We modify the hybrid mechanism and incorporate a discrete "twin" symmetry, thereby yielding a viable, natural and EFT-controlled model of non-supersymmetric low-scale inflation, "Twinflation". Analogously to Twin Higgs models, the discrete exchange-symmetry with a "twin" sector reduces quadratic sensitivity in the inflationary potential to ultra-violet physics, at the root of the hierarchy problem. The observed phase of inflation takes place on a hilltop-like potential but without fine-tuning of the initial inflaton position in field-space. We also show that all parameters of the model can take natural values, below any associated EFT-cutoff mass scales and field values, thus ensuring straightforward theoretical control. We discuss the basic phenomenological considerations and constraints, as well as possible future directions.

   hep-phastro-ph.COgr-qcJHEP(2021)·5 citations
10. 10*

    Double Monodromy Inflation: A Gravity Waves Factory for CMB-S4, LiteBIRD and LISA

    Guido D'Amico🇮🇹 · Nemanja Kaloper🇺🇸 · Alexander Westphal🇩🇪

    We consider a short rollercoaster cosmology based on two stages of monodromy inflation separated by a stage of matter domination, generated after the early inflaton falls out of slow roll. If the first stage is controlled by a flat potential, $V\sim {\varphi }^p$ with $p<1$ and lasts $\mathcal{N}\sim 30-40$ efolds, the scalar and tensor perturbations at the largest scales will fit the CMB perfectly, and produce relic gravity waves with $0.02\lesssim r\lesssim 0.06$, which can be tested by LiteBIRD and CMB-S4 experiments. If in addition the first inflaton is strongly coupled to a hidden sector $U(1)$, there will be an enhanced production of vector fluctuations near the end of the first stage of inflation. These modes convert rapidly to tensors during the short epoch of matter domination, and then get pushed to superhorizon scales by the second stage of inflation, lasting another $20-30$ efolds. This band of gravity waves is chiral, arrives today with wavelengths in the range of $10^8$ km, and with amplitudes greatly enhanced compared to the long wavelength CMB modes by vector sources. It is therefore accessible to LISA. Thus our model presents a rare early universe theory predicting several simultaneous signals testable by a broad range of gravity wave searches in the very near future.

    ↳ hep-thastro-ph.COgr-qchep-phPRD(2021)·37 citations
11. 11*

    The chiral phase transition and equation of state in the chiral imbalance

    Qing-Wu Wang🇨🇳 · Chao shi🇨🇳 · Hong-Shi Zong🇨🇳

    The chiral phase transition and equation of state are studied within a new self-consistent mean-field approximation of the two-flavor Nambu$-$Jona-Lasinio model. In this newly developed model, modifications to the chemical potential $\mu$ and chiral chemical potential ${\mu }_5$ is naturally included by adding vector and axial-vector channels from Fierz-transformed Lagrangian to the standard Lagrangian. In proper-time scheme, the chiral phase transition is a crossover in the $T-\mu$ plane. But when ${\mu }_5$ is increased, our study shows that there may exist first order phase transition. Furthermore, the chiral imbalance will soften the equation of state of quark matter. The mass-radius relations and tidal deformability of quark stars are calculated. As ${\mu }_5$ increases, the maximum mass and radius decrease. The vector channel and axial-vector channel have opposite influence on the equation of state. However, when EOS is constrained by astronomical observations, the shape of the mass-radius curve can be used to determine whether there is chiral imbalance in the dense object, and thus indirectly proving the CP violation in the dense matter. Our study shows a different influence of the chiral imbalance on the chiral phase transition in contrary to tree-momentum-cutoff scheme.

    ↳ nucl-thhep-phCPC(2021)·3 citations
12. 12*

    X-ray Intraday Variability of the TeV Blazar PKS 2155-304 with Suzaku During 2005-2014

    Zhongli Zhang🇨🇳 · Alok C. Gupta🇨🇳 · Haritma Gaur🇮🇳 · Paul J. Wiita🇺🇸 · Tao An🇨🇳 · Yang Lu🇨🇳 · Shida Fan🇨🇳 · Haiguang Xu🇨🇳

    We have examined 13 pointed observations of the TeV emitting high synchrotron peak blazar PKS 2155-304, taken by the Suzaku satellite throughout its operational period. We found that the blazar showed large-amplitude intraday variabilities in the soft (0.8 - 1.5 keV) and the hard (1.5 - 8.0 keV) bands in the light curves. Spectral variability on intraday timescales is estimated using the hardness ratio. The blazar usually becomes harder when brighter and vice versa, following the typical behavior of high synchrotron peak blazars. The power spectral density (PSD) analyses of 11 out of 13 light curves in the total energy (0.8 - 8.0 keV) are found to be red-noise dominated, with power-law spectral indices that span a large range, from -2.81 to -0.88. Discrete correlation function analyses of all the 13 light curves between the soft and the hard bands show that they are well correlated and peak at, or very close to, zero lag. This indicates that the emissions in soft and hard bands are probably cospatial and emitted from the same population of leptons. Considering fluxes versus variability timescales, we found no correlation on intraday timescales, implying that X-ray emission from PKS 2155-304 is not dominated by simple changes in the Doppler factor. We briefly discuss the most likely emission mechanisms responsible for the observed flux and spectral variabilities and place constraints on magnetic field strength and Lorentz factors of the electrons emitting the X-rays in the most likely scenario.

    ↳ astro-ph.HEhep-phApJ(2021)·23 citations
13. 13*

    Three-body interactions from the finite-volume QCD spectrum

    Ruairí Brett🇺🇸 · Chris Culver🇬🇧 · Maxim Mai🇺🇸 · Andrei Alexandru🇺🇸 · Michael Döring🇺🇸 · Frank X. Lee🇺🇸

    We perform a fit of the finite-volume QCD spectrum of three pions at maximal isospin to constrain the three-body force. We use the unitarity-based relativistic three-particle quantization condition, with the GWUQCD spectrum obtained at 315 MeV and 220 MeV pion mass in two-flavor QCD. For the heavier pion mass we find that the data is consistent with a constant contact term close to zero, whereas for the lighter mass we see a statistically significant energy dependence in tension with the prediction of leading order ChPT. Our results also suggest that with enough three-body energy levels, the two-body amplitude could be constrained.

    ↳ hep-lathep-phnucl-thPRD(2021)·73 citations
14. 14*

    Tachyonic de Sitter solutions of 10d type II supergravities

    David Andriot🇦🇹

    Cosmological models of the early or late universe exhibit (quasi) de Sitter space-times with different stability properties. Considering models derived from string theory, the swampland program does not provide for now a definite characterisation of this stability. In this work we focus on de Sitter solutions of 10d type II supergravities, candidates for classical de Sitter string backgrounds: surprisingly, all known examples are unstable with ${\eta }_V<-1$. We aim at proving the existence of such a systematic tachyon, and getting formally a bound on the value of ${\eta }_V$. To that end, we develop three methods, giving us various sufficient conditions for having a tachyon upon assumptions, in analogy with de Sitter no-go theorems. Our analysis eventually indicates the existence of variety of different tachyons, and related bounds on ${\eta }_V$. We use this knowledge to find 10 new de Sitter solutions of type IIB supergravity, that have tachyons of a different kind, higher ${\eta }_V$ values and new 6d geometries. One solution even appears to be stable, with however non-compact extra dimensions.

    ↳ hep-thastro-ph.COgr-qchep-phFortsch.Phys.(2021)·42 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.