Thu·Apr 19, 2018Thursday·April 19, 2018

1. 01*

   Quantum Field Theory of Particle Oscillations: Neutron-Antineutron Conversion

   Anca Tureanu🇫🇮

   We formulate the quantum field theory description of neutron-antineutron oscillations in the framework of canonical quantization, in analogy with the Bardeen--Cooper--Schrieffer (BCS) theory and the Nambu--Jona-Lasinio model. The physical vacuum of the theory is a condensate of pairs of {\it would-be neutrons and antineutrons} in the absence of the baryon-number violating interaction. The quantization procedure defines uniquely the mixing of massive Bogoliubov quasiparticle states which represent the neutron. In spite of not being mass eigenstates, neutron and antineutron states are defined on the physical vacuum and the oscillation formulated in asymptotic states. The exchange of baryonic number with the vacuum condensate engenders what may be observed as neutron-antineutron oscillation. The convergence between the present canonical approach and the Lagrangian/path integral approach to neutron oscillations is shown by the calculation of the anomalous (baryon-number violating) propagators. The quantization procedure proposed here can be extended to neutrino oscillations and, in general, to any particle oscillations.

   hep-phhep-thPRD(2018)·15 citations
2. 02*

   Workshop on Pion-Kaon Interactions (PKI2018) Mini-Proceedings. Editors: M. Amaryan, Ulf-G. Meißner, C. Meyer, J. Ritman, and I. Strakovsky

   M. Amaryan · M. Baalouch · G. Colangelo · J. R. de Elvira · D. Epifanov · A. Filippi · B. Grube · V. Ivanov · B. Kubis · P. M. Lo · M. Mai · V. Mathieu and 12 other authors

   This volume is a short summary of talks given at the PKI2018 Workshop organized to discuss current status and future prospects of pi-K interactions. The precise data on pi-K interaction will have a strong impact on strange meson spectroscopy and form factors that are important ingredients in the Dalitz plot analysis of a decays of heavy mesons as well as precision measurement of Vus matrix element and therefore on a test of unitarity in the first raw of the CKM matrix. The workshop has combined the efforts of experimentalists, Lattice QCD, and phenomenology communities. Experimental data relevant to the topic of the workshop were presented from the broad range of different collaborations like CLAS, GlueX, COMPASS, BaBar, BELLE, BESIII, VEPP-2000, and LHCb. One of the main goals of this workshop was to outline a need for a new high intensity and high precision secondary KL beam facility at JLab produced with the 12 GeV electron beam of CEBAF accelerator. This workshop is a successor of the workshops Physics with Neutral Kaon Beam at JLab [1] held at JLab, February, 2016; Excited Hyperons in QCD Thermodynamics at Freeze-Out [2] held at JLab, November, 2016; New Opportunities with High-Intensity Photon Sources [3] held at CUA, February, 2017. Further details about the PKI2018 Workshop can be found on the web page of the conference: http://www.jlab.org/conferences/pki2018/ .

   hep-phhep-exnucl-exnucl-th2 citations
3. 03*

   Semi-leptonic decays of $B^{\ast }$, $B_s^{\ast }$, and $B_c^{\ast }$ with the Bethe-Salpeter method

   Tianhong Wang🇨🇳 · Yue Jiang🇨🇳 · Tian Zhou🇨🇳 · Xiao-Ze Tan🇨🇳 · Guo-Li Wang🇨🇳

   In this paper we study the semileptonic decays of $B^{\ast }$, $B_s^{\ast }$, and $B_c^{\ast }$ by using the Bethe-Salpeter method with instantaneous approximation. Both the $V\to P{l}^{-}{\bar{\nu }}_l$ and $V\to V{l}^{-}{\bar{\nu }}_l$ cases are considered. The largest partial width of these channels is of the order of $10^{-14}$ GeV. The branching ratios of these semileptonic decays are also estimated by using the partial width of the one photon decay channel to approximate the total width. For $B^{\ast -}\to D^{(\ast )0}{e}^{-}{\bar{\nu }}_e$ and $B_s^{\ast 0}\to D_s^{(\ast )+}{e}^{-}{\bar{\nu }}_e$, the branching ratios are of the order of $10^{-8}$ and $10^{-7}$, respectively. For $B_c^{\ast -}$, the $J/\psi e^{-}{\bar{\nu }}_e$ and $B_s^{\ast 0}{e}^{-}{\bar{\nu }}_e$ channels have the largest branching ratio, which is of the order of $10^{-6}$.

   hep-phJ.Phys.G(2018)·13 citations
4. 04*

   Wigner solution of the quark gap equation

   Zhu-Fang Cui🇨🇳 · Shu-Sheng Xu🇨🇳 · Bo-Lin Li🇨🇳 · An Sun🇨🇳 · Jing-Bo Zhang🇨🇳 · Hong-Shi Zong🇨🇳

   Solutions and their evolutions of the quark gap equation are studied within the Nambu-Jona--Lasinio model, which is a basic issue for studying the QCD phase structure and locating the possible critical end point. It is shown that in the chiral limit case of the vacuum, chiral symmetry will hold if the coupling strength $G$ is small, then the system only has the Wigner solution at $M=0$. If increasing $G$, two symmetric minima will appear as the positive and `negative' Nambu solutions, however, the solution $M=0$ now corresponds to a maximum instead of a minimum of the thermodynamical potential, so is not a physically stable state anymore (we call it `pseudo-Wigner solution'). Besides, it is shown that as the current quark mass $m$ increases, the pseudo-Wigner solution will become negative, and disappear together with the negative Nambu solution if $m$ is large enough. Similar things happen if we increase the temperature or quark chemical potential $\mu$. Some interesting phenomenon is, from some $\mu$ a second local minimum will show up. As $\mu$ increases gradually, it will be stabler than the Nambu solution, survives even the Nambu solution disappears, and approaches $m$, which are just the features of the Wigner solution we expect.

   hep-phEPJC(2018)·19 citations
5. 05*

   A new algorithm towards quasi-Wigner solution of the gap equation beyond the chiral limit

   Shu-Sheng Xu🇨🇳 · Zhu-Fang Cui🇨🇳 · An Sun🇨🇳 · Hong-Shi Zong🇨🇳

   We propose a new algorithm to solve the quasi-Wigner solution of the gap equation beyond chiral limit. Employing a Gaussian gluon model and rainbow truncation, we find that the quasi-Wigner solution exists in a limited region of current quark mass, $m<43.1$ MeV, at zero temperature $T$ and zero chemical potential $\mu$. The difference between Cornwall-Jackiw-Tomboulis (CJT) effective actions of quasi-Wigner and Nambu-Goldstone solutions shows that the Nambu-Goldstone solution is chosen by physics. Moreover, the quasi-Wigner solution is studied at finite temperature and chemical potential, the far infrared mass function of quasi-Wigner solution is negative and decrease along with $T$ at $\mu =0$. Its susceptibility is divergent at certain temperature with small $m$, and this temperature decreases along with $m$. Taking $T=80$ MeV as an example, the quasi-Wigner solution is shown at finite chemical potential upto $\mu =350$ MeV as well as Nambu solution, the coexistence of these two solutions indicates that the QCD system suffers the first order phase transition. The first order chiral phase transition line is determined by the difference of CJT effective actions.

   hep-phJ.Phys.G(2018)·15 citations
6. 06*

   Leptogenesis in Cosmological Relaxation with Particle Production

   Minho Son🇰🇷 · Fang Ye🇰🇷 · Tevong You🇬🇧

   Cosmological relaxation of the electroweak scale is improved by using particle production to trap the relaxion. We combine leptogenesis with such a relaxion model that has no extremely small parameters or large e-foldings. Scanning happens after inflation--now allowed to be at a high scale--over a sub-Planckian relaxion field range for an $\mathcal{O}(100)$ TeV cut-off scale of new physics. Particle production by the relaxion also reheats the universe and generates the baryonic matter-antimatter asymmetry. We propose a realisation in which out-of-equilibrium leptons, produced by the relaxion, scatter with the thermal bath through interactions that violate CP and lepton number via higher-dimensional operators. Such a minimal effective field theory setup, with no new physics below the cut-off, naturally decouples new physics while linking leptogenesis to relaxion particle production; the baryon asymmetry of the universe can thus be intrinsically tied to a weak scale hierarchy.

   hep-phastro-ph.COPRD(2019)·17 citations
7. 07*

   Dominant production of heavier Higgs bosons through vector boson fusion in NMSSM

   Debottam Das🇮🇳

   We study the features of the additional Higgs bosons in the Next-to-Minimal Supersymmetric Standard Model where the lightest beyond Standard Model Higgs boson does not dominantly couple to up-type quarks. The new state is dominantly singlet-like while it can also accommodate a small down-type Higgs component. The gluon-gluon fusion cannot be adequate enough for such a Higgs production. We show that the vector-boson fusion may become the leading production mechanism to probe this new scalar at the LHC. Using the existing 13 TeV LHC data for an integrated luminosity $36.1f{b}^{-1}$, we show the LHC constraints on the parameter space. Finally, we also study the reach of the planned high luminosity LHC ($\mathcal{L}=3{\mathrm{ab}}^{-1}$ at $\sqrt{s}=$~14 TeV) and the proposed high energy upgrade of the LHC ($\mathcal{L}=15{\mathrm{ab}}^{-1}$ at $\sqrt{s}=$~27 TeV) to probe this singlet-like Higgs scalar.

   hep-phPRD(2019)·11 citations
8. 08*

   Doubly charmed tetraquarks in a diquark-antidiquark model

   Xiaojun Yan🇨🇳 · Bin Zhong🇨🇳 · Ruilin Zhu🇨🇳

   We study the spectra of the doubly charmed tetraquark states in a diquark-antidiquark model. The doubly charmed tetraquark states form an antitriplet and a sextet configurations according to flavor SU(3) symmetry. For the tetraquark state $[q{q}^{\prime }][\bar{c}\bar{c}]$, we show the mass for both bound and excited states. The two-body decays of tetraquark states $T^{cc}[0^{+}]$ and $T^{cc}[1^{--}]$ to charmed mesons have also been studied. In the end,the doubly charmed tetraquarks decays to a charmed baryon and a light baryon have been studied in the SU(3) flavor symmetry.

   hep-phhep-exInt.J.Mod.Phys.A(2018)·30 citations
9. 09*

   Higgs portal dark matter in non-thermal cosmologies

   Edward Hardy🇬🇧

   A scalar particle with a relic density set by annihilations through a Higgs portal operator is a simple and minimal possibility for dark matter. However, assuming a thermal cosmological history this model is ruled out over most of parameter space by collider and direct detection constraints. We show that in theories with a non-thermal cosmological history Higgs portal dark matter is viable for a wide range of dark matter masses and values of the portal coupling, evading existing limits. In particular, we focus on the string theory motivated scenario of a period of late time matter domination due to a light modulus with a decay rate that is suppressed by the Planck scale. Dark matter with a mass < GeV is possible without additional hidden sector states, and this can have astrophysically relevant self-interactions. We also study the signatures of such models at future direct, indirect, and collider experiments. Searches for invisible Higgs decays at the high luminosity LHC or an e+ e- collider could cover a significant proportion of the parameter space for low mass dark matter, and future direct detection experiments will play a complementary role.

   hep-phJHEP(2018)·64 citations
10. 10*

    Exploring dynamical CP violation induced baryogenesis by gravitational waves and colliders

    Fa Peng Huang🇰🇷 · Zhuoni Qian🇰🇷 · Mengchao Zhang🇰🇷

    By assuming a dynamical source of CP violation, the tension between sufficient CP violation for successful electroweak baryogenesis and strong constraints from current electric dipole moment measurements could be alleviated. We study how to explore such scenarios through gravitational wave detection, collider experiments, and their possible synergies with a well-studied example.

    hep-phPRD(2018)·68 citations
11. 11*

    Systematic approximation of multi-scale Feynman integrals

    Sophia Borowka🇨🇭 · Thomas Gehrmann🇨🇭 · Daniel Hulme🇨🇭

    An algorithm for the systematic analytical approximation of multi-scale Feynman integrals is presented. The algorithm produces algebraic expressions as functions of the kinematical parameters and mass scales appearing in the Feynman integrals, allowing for fast numerical evaluation. The results are valid in all kinematical regions, both above and below thresholds, up to in principle arbitrary orders in the dimensional regulator. The scope of the algorithm is demonstrated by presenting results for selected two-loop three-point and four-point integrals with an internal mass scale that appear in the two-loop amplitudes for Higgs+jet production.

    hep-phJHEP(2018)·17 citations
12. 12*

    Displaced vertex signature of type-I seesaw

    Sudip Jana🇺🇸 · Nobuchika Okada🇺🇸 · Digesh Raut🇺🇸

    A certain class of new physics models includes long-lived particles which are singlet under the Standard Model (SM) gauge group.A displaced vertex is a spectacular signature to probe such particles productions at the high energy colliders, with a negligible SM background. In the context of the minimal gauged $B-L$ extended SM, we consider a pair creation of Majorana right-handed neutrinos (RHNs) at the high energy colliders through the production of the SM and the $B-L$ Higgs bosons and their subsequent decays into RHNs. With parameters reproducing the neutrino oscillation data, we show that the RHNs are long-lived and their displaced vertex signature can be observed at the next generation displaced vertex search experiments, such as the HL-LHC, the MATHUSLA, the LHeC, and the FCC-eh.We find that the lifetime of the RHNs is controlled by the lightest light neutrino mass, which leads to a correlation between the displaced vertex search and the search limit of the future neutrinoless double beta-decay experiments.

    hep-phhep-exPRD(2018)·42 citations
13. 13*

    Hybrid seesaw leptogenesis and TeV singlets

    Kaustubh Agashe🇺🇸 · Peizhi Du🇺🇸 · Majid Ekhterachian🇺🇸 · Chee Sheng Fong🇧🇷 · Sungwoo Hong🇺🇸 · Luca Vecchi🇨🇭

    The appealing feature of inverse seesaw models is that the Standard Model (SM) neutrino mass emerges from the exchange of TeV scale singlets with sizable Yukawa couplings, which can be tested at colliders. However, the tiny Majorana mass splitting between TeV singlets, introduced to accommodate small neutrino masses, is left unexplained. Moreover, we argue that these models suffer from a structural limitation that prevents a successful leptogenesis if one insists on having unsuppressed Yukawa couplings and TeV scale singlets. In this work we propose a hybrid seesaw model, where we replace the mass splitting with a coupling to a high scale seesaw module including a TeV scalar. We show that this structure achieves the goal of filling both the above gaps with couplings of order unity. The necessary structure automatically arises embedding the seesaw mechanism in composite Higgs models, but may also be enforced by new gauge symmetries in a weakly-coupled theory. Our hybrid seesaw models have distinguishing features compared to the standard high scale type-I seesaw and inverse seesaw. Firstly, they have much richer phenomenology. Indeed, they generally predict new TeV scale physics (including scalars) potentially accessible at present and future colliders, whereas weakly-coupled versions may also have astrophysical and cosmological signatures due to the presence of a light Nambu-Goldstone boson coupled to neutrinos. Secondly, our scenario features an interesting interplay between high scale and TeV scale physics in leptogenesis and enlarges the range of allowed high scale singlet masses beyond the usual $\sim 10^9-10^{15}$ GeV, without large hierarchies in the Yukawa couplings nor small mass splitting among the singlets.

    hep-phPLB(2018)·14 citations
14. 14*

    Production and hadronic decays of Higgs bosons in heavy ion collisions

    Edmond L. Berger🇺🇸 · Jun Gao🇨🇳 · Adil Jueid🇨🇳 · Hao Zhang🇨🇳

    We examine Higgs boson production and decay in heavy-ion collisions at the LHC and future colliders. Owing to the long lifetime of the Higgs boson, its hadronic decays may experience little or no screening from the hot and dense quark-gluon plasma whereas jets from hard scattering processes and from decays of the electro-weak gauge bosons and the top-quark suffer significant energy loss. This distinction can lead to enhanced signal to background ratios in hadronic decay channels and thus, for example, provide alternative ways to probe the Yukawa coupling of the Higgs boson to the bottom quark and its lifetime.

    hep-phPRL(2019)·9 citations
15. 15*

    Levy analysis of Bose-Einstein correlation in pp collisions at s 7 TeV measured with the ATLAS

    V.A. Schegelsky🇷🇺

    Bose-Einstein correlations in proton-proton collisions is an effective tool to study the space structure of the production amplitude. Usually rather simple parametrization of particle-emission distribution function has been used - exponential or gaussian form. However if one consider a particle source as an expanding media the symmetric Levy distribution as the generalization exponential can be used.Then additional parameter - the index of stability - will appear. All parameters dependencies on the charged particle density and on the mean transverse momentum of the pion/hadron in the correlated pair are investigated.

    hep-phPhys.Part.Nucl.Lett.(2019)·5 citations
16. 16*

    Bayesian parameter estimation for relativistic heavy-ion collisions

    Jonah E. Bernhard🇺🇸

    I develop and apply a Bayesian method for quantitatively estimating properties of the quark-gluon plasma (QGP), an extremely hot and dense state of fluid-like matter created in relativistic heavy-ion collisions. The QGP cannot be directly observed -- it is extraordinarily tiny and ephemeral, about $10^{-14}$ meters in size and living $10^{-23}$ seconds before freezing into discrete particles -- but it can be indirectly characterized by matching the output of a computational collision model to experimental observations. The model, which takes the QGP properties of interest as input parameters, is calibrated to fit the experimental data, thereby extracting a posterior probability distribution for the parameters. In this dissertation, I construct a specific computational model of heavy-ion collisions and formulate the Bayesian parameter estimation method, which is based on general statistical techniques. I then apply these tools to estimate fundamental QGP properties, including its key transport coefficients and characteristics of the initial state of heavy-ion collisions. Perhaps most notably, I report the most precise estimate to date of the temperature-dependent specific shear viscosity $\eta /s$, the measurement of which is a primary goal of heavy-ion physics. The estimated minimum value is $\eta /s=0.085_{-0.025}^{+0.026}$ (posterior median and 90% uncertainty), remarkably close to the conjectured lower bound of $1/4\pi \simeq 0.08$. The analysis also shows that $\eta /s$ likely increases slowly as a function of temperature. Other estimated quantities include the temperature-dependent bulk viscosity $\zeta /s$, the scaling of initial state entropy deposition, and the duration of the pre-equilibrium stage that precedes QGP formation.

    ↳ nucl-thhep-phnucl-exstat.AP108 citations
17. 17*

    Modular symmetry and non-Abelian discrete flavor symmetries in string compactification

    Tatsuo Kobayashi🇯🇵 · Satoshi Nagamoto🇯🇵 · Shintaro Takada🇯🇵 · Shio Tamba🇯🇵 · Takuya H. Tatsuishi🇯🇵

    We study the modular symmetry in magnetized D-brane models on $T^2$. Non-Abelian flavor symmetry $D_4$ in the model with magnetic flux $M=2$ (in a certain unit) is a subgroup of the modular symmetry. We also study the modular symmetry in heterotic orbifold models. The $T^2/Z_4$ orbifold model has the same modular symmetry as the magnetized brane model with $M=2$, and its flavor symmetry $D_4$ is a subgroup of the modular symmetry.

    ↳ hep-thhep-phPRD(2018)·131 citations
18. 18*

    Unexpected Dip in the Solar Gamma-Ray Spectrum

    Qing-Wen Tang🇺🇸 · Kenny C. Y. Ng🇮🇱 · Tim Linden🇺🇸 · Bei Zhou🇺🇸 · John F. Beacom🇺🇸 · Annika H. G. Peter🇺🇸

    The solar disk is a bright source of multi-GeV gamma rays, due to the interactions of hadronic cosmic rays with the solar atmosphere. However, the underlying production mechanism is not understood, except that its efficiency must be greatly enhanced by magnetic fields that redirect some cosmic rays from ingoing to outgoing before they interact. To elucidate the nature of this emission, we perform a new analysis of solar atmospheric gamma rays with 9 years of Fermi-LAT data, which spans nearly the full 11-year solar cycle. We detect significant gamma-ray emission from the solar disk from 1 GeV up to $\gtrsim 200$ GeV. The overall gamma-ray spectrum is much harder ($\sim E_{\gamma }^{-2.2}$) than the cosmic-ray spectrum ($\sim E_{\mathrm{CR}}^{-2.7}$). We find a clear anticorrelation between the solar cycle phase and the gamma-ray flux between 1-10 GeV. Surprisingly, we observe a spectral dip between $\sim$30-50 GeV in an otherwise power-law spectrum. This was not predicted, is not understood, and may provide crucial clues to the gamma-ray emission mechanism. The flux above 100 GeV, which is brightest during the solar minimum, poses exciting opportunities for HAWC, LHAASO, IceCube, and KM3NeT.

    ↳ astro-ph.HEastro-ph.SRhep-phPRD(2018)·62 citations
19. 19*

    Vacuum structure of Yang-Mills theory as a function of $\theta$

    Kyle Aitken🇺🇸 · Aleksey Cherman🇺🇸 · Mithat Ünsal🇺🇸

    It is believed that in $SU(N)$ Yang-Mills theory observables are $N$-branched functions of the topological $\theta$ angle. This is supposed to be due to the existence of a set of locally-stable candidate vacua, which compete for global stability as a function of $\theta$. We study the number of $\theta$ vacua, their interpretation, and their stability properties using systematic semiclassical analysis in the context of adiabatic circle compactification on ${\mathbb{R}}^3\times S^1$. We find that while observables are indeed N-branched functions of $\theta$, there are only $\approx N/2$ locally-stable candidate vacua for any given $\theta$. We point out that the different $\theta$ vacua are distinguished by the expectation values of certain magnetic line operators that carry non-zero GNO charge but zero 't Hooft charge. Finally, we show that in the regime of validity of our analysis YM theory has spinodal points as a function of $\theta$, and gather evidence for the conjecture that these spinodal points are present even in the ${\mathbb{R}}^4$ limit.

    ↳ hep-thhep-phJHEP(2018)·33 citations
20. 20*

    A microscopic model for an emergent cosmological constant

    Alejandro Perez🇫🇷 · Daniel Sudarsky🇲🇽 · James D. Bjorken🇺🇸

    The value of the cosmological constant is explained in terms of a noisy diffusion of energy from the low energy particle physics degrees of freedom to the fundamental Planckian granularity which is expected from general arguments in quantum gravity. The quantitative success of our phenomenological model is encouraging and provides possibly useful insights about physics at the scale of quantum gravity.

    ↳ gr-qcastro-ph.COhep-phhep-thInt.J.Mod.Phys.D(2018)·40 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.