Fri·Aug 19, 2016Friday·August 19, 2016

1. 01*

   Modelling duality between bound and resonant meson spectra by means of free quantum motions on the de Sitter space time dS4

   M. Kirchbach🇲🇽 · C. Compean🇲🇽

   We seek for a pair of a well and barrier potentials such that the real parts of the complex energies of the resonances transmitted through the barrier equal the energies of the states bound within the well and find the hyperbolic Poeschl-Teller barrier, ~sech^2\rho, and the trigonometric Scarf well, ~ \sec^2\chi. The potentials are shown to be conformally symmetric by the aid of the de Sitter space time, dS4, related to flat conformal space time by a conformal map. Namely, we transform the quantum mechanical wave equations with the above potentials to free quantum motions on the respective open time like hyperbolic and the closed space like hyper spherical, S3, geodesics of dS4, the former by itself is related to Minkowski space time by a conformal map.We formulate a conformal symmetry respecting classification scheme for mesons seen either as resonances in scattering, or as states bound within a potential, according to trajectories in which the total spin of the meson, l-depends linearly on the first power of the invariant mass, M, and not as in the canonical Regge formalism on the squared mass.We analyze 71 reported mesons in this scheme and in finding good agreement with data predict the masses of 12 missing mesons. We observe that on S3 the color quantum number of mesons is limited to neutral. To the amount physics is independent of the choice of the set of coordinates, this property remains valid in the flat geometry too. We conclude on the usefulness of conformal maps of flat to curved space times as tools for modelling and interpreting the color neutrality of hadrons required by the confinement phenomenon and on the relevance of trigonometric and hyperbolic potentials for constituent quark models. Finally, all involved potentials have been motivated by Wilson loops with cusps.

   hep-phEPJA(2016)·10 citations
2. 02*

   The Strong Decays of X(3940) and X(4160)

   Zhi-Hui Wang🇨🇳 · Yi Zhang · Libo Jiang🇺🇸 · Tian-Hong Wang🇨🇳 · Yue Jiang🇨🇳 · Guo-Li Wang🇨🇳

   The new mesons $X(3940)$ and $X(4160)$ have been found by Belle Collaboration in the processes $e^{+}{e}^{-}\to J/\psi D^{(\ast )}{\bar{D}}^{(\ast )}$. Considering $X(3940)$ and $X(4160)$ as ${\eta }_c(3S)$ and ${\eta }_c(4S)$ states, the two-body open charm OZI-allowed strong decay of ${\eta }_c(3S)$ and ${\eta }_c(4S)$ are studied by the improved Bethe-Salpeter method combine with the ${}^3{P}_0$ model. The strong decay width of ${\eta }_c(3S)$ is ${\Gamma }_{{\eta }_c(3S)}=(33.5_{-15.3}^{+18.4})$ MeV, which is closed to the result of $X(3940)$, therefore, ${\eta }_c(3S)$ is a good candidate of $X(3940)$. The strong decay width of ${\eta }_c(4S)$ is ${\Gamma }_{{\eta }_c(4S)}=(69.9_{-21.1}^{+22.4})$ MeV, considering the errors of the results, it's closed to the lower limit of $X(4160)$. But the ratio of the decay width $\frac{\Gamma (D{\bar{D}}^{\ast })}{\Gamma (D^{\ast }{\bar{D}}^{\ast })}$ of ${\eta }_c(4S)$ is larger than the experimental data of $X(4160)$. According to the above analysis, ${\eta }_c(4S)$ is not the candidate of $X(4160)$, and more investigations of $X(4160)$ is needed.

   hep-phEPJC(2017)·13 citations
3. 03*

   New physics contributions in $B\to \pi \tau \bar{\nu }$ and $B\to \tau \bar{\nu }$

   Minoru Tanaka🇯🇵 · Ryoutaro Watanabe🇰🇷

   We study possible new physics contributions in $B\to \pi \tau \bar{\nu }$ and $B\to \tau \bar{\nu }$ employing the model-independent effective Lagrangian that describes the quark-level transition $b\to u\tau \nu$ at low energies. The decay rate of $B\to \pi \tau \bar{\nu }$ and its theoretical uncertainty are evaluated using the $B\to \pi$ form factors given by recent lattice QCD studies. Comparing theoretical results with the current experimental data, $\mathcal{B}(B\to \pi \tau \bar{\nu })<2.5\times 10^{-4}$ and $\mathcal{B}(B\to \tau \bar{\nu })=(1.14\pm 0.22)\times 10^{-4}$, we obtain constraints on the Wilson coefficients that quantify potential new physics. We also present the expected sensitivity of the SuperKEKB/Belle~II experiment.

   hep-phhep-exPTEP(2017)·18 citations
4. 04*

   Determination of the top-quark mass from hadro-production of single top-quarks

   S.Alekhin🇩🇪 · S.Moch🇩🇪 · S.Thier🇩🇪

   We present a new determination of the top-quark mass $m_t$ based on the experimental data from the Tevatron and the LHC for single-top hadro-production. We use the inclusive cross sections of $s$- and $t$-channel top-quark production to extract $m_t$ and to minimize the dependence on the strong coupling constant and the gluon distribution in the proton compared to the hadro-production of top-quark pairs. As part of our analysis we compute the next-to-next-to-leading order approximation for the $s$-channel cross section in perturbative QCD based on the known soft-gluon corrections and implement it in the program Hathor for the numerical evaluation of the hadronic cross section. Results for the top-quark mass are reported in the $\overline{MS}$ and in the on-shell renormalization scheme.

   hep-phPLB(2016)·27 citations
5. 05*

   Small size sources of secondaries observed in pp-collisions via Bose-Einstein correlations at the LHC ATLAS experiment

   V.A. Schegelsky🇷🇺 · M.G. Ryskin🇷🇺

   Bose-Einstein correlations in proton-proton collisions at the LHC are well descried by the formula with two different scales. It is shown for the first time that the pions are produced by few small size sources distributed over a much larger area in impact parameter space occupied by the interaction amplitude. The dependence of the two radii obtained in this procedure on the charged particle density and the mean transverse momentum of the pion/hadron in the correlated pair are discussed.

   hep-ph2 citations
6. 06*

   CP and other Symmetries of Symmetries

   Andreas Trautner🇩🇪

   Outer automorphisms of symmetries ("symmetries of symmetries") in relativistic quantum field theories are studied, including charge conjugation (C), space-reflection (P) , and time-reversal (T) transformations. The group theory of outer automorphisms is pedagogically introduced and it is shown that CP transformations are special outer automorphisms of the global, local, and space-time symmetries of a theory. It is shown that certain discrete groups allow for a group theoretical prediction of parameter independent CP violating complex phases with fixed geometrical values. The remainder of this thesis pioneers the study of outer automorphisms which are not related to C, P, or T. It is shown how outer automorphisms, in general, relate symmetry invariants and, in theories with spontaneous symmetry breaking, imply relations between different vacuum expectation values. Thereby, outer automorphisms can give rise to emergent symmetries. An example model with a discrete symmetry and three copies of the Standard Model Higgs field is discussed, in which the rich outer automorphism structure completely fixes the Higgs VEVs in their field space direction, including CP violating relative phases. This underlies the phenomenon of spontaneous geometrical CP violation. The possible relevance of outer automorphisms for a wide field of future studies is highlighted.

   hep-phcond-mat.otherhep-th27 citations
7. 07*

   The reheating era leptogenesis in models with seesaw mechanism

   Yuta Hamada🇯🇵 · Koji Tsumura🇯🇵 · Daiki Yasuhara🇯🇵

   Observed baryon asymmetry can be achieved not only by the decay of right-handed neutrinos but also by the scattering processes in the reheating era. In the latter scenario, new physics in high energy scale does not need to be specified, but only two types of the higher dimensional operator of the standard model particles are assumed in the previous work. In this paper, we examine the origin of the higher dimensional operators assuming models with a certain seesaw mechanism at the high energy scale. The seesaw mechanism seems to be a simple realization of the reheating era leptogenesis because the lepton number violating interaction is included. We show that the effective interaction giving CP violating phases is provided in the several types of models and also the reheating era leptogenesis actually works in such models. Additionally, we discuss a possibility for lowering the reheating temperature in the radiative seesaw models, where the large Yukawa coupling is naturally realized.

   hep-phastro-ph.COPRD(2017)·10 citations
8. 08*

   Thermal Electromagnetic Radiation in Heavy-Ion Collisions

   R. Rapp🇺🇸 · H. van Hees🇩🇪

   We review the potential of precise measurements of electromagnetic probes in relativistic heavy-ion collisions for the theoretical understanding of strongly interacting matter. The penetrating nature of photons and dileptons implies that they can carry undistorted information about the hot and dense regions of the fireballs formed in these reactions and thus provide a unique opportunity to measure the electromagnetic spectral function of QCD matter as a function of both invariant mass and momentum. In particular we report on recent progress on how the medium modifications of the (dominant) isovector part of the vector current correlator ($\rho$ channel) can shed light on the mechanism of chiral symmetry restoration in the hot and/or dense environment. In addition, thermal dilepton radiation enables novel access to (a) the fireball lifetime through the dilepton yield in the low invariant-mass window $0.3\mathrm{GeV}\le M\le 0.7\mathrm{GeV}$, and (b) the early temperatures of the fireball through the slope of the invariant-mass spectrum in the intermediate-mass region ($1.5\mathrm{GeV}<M<2.5\mathrm{GeV}$). The investigation of the pertinent excitation function suggests that the beam energies provided by the NICA and FAIR projects are in a promising range for a potential discovery of the onset of a first order phase transition, as signaled by a non-monotonous behavior of both low-mass yields and temperature slopes.

   hep-phnucl-exnucl-thEPJA(2016)·34 citations
9. 09*

   CGC factorization for forward particle production in proton-nucleus collisions at next-to-leading order

   E. Iancu🇫🇷 · A.H. Mueller🇺🇸 · D.N. Triantafyllopoulos🇮🇹

   Within the Color Glass Condensate effective theory, we reconsider the next-to-leading order (NLO) calculation of the single inclusive particle production at forward rapidities in proton-nucleus collisions at high energy. Focusing on quark production for definiteness, we establish a new factorization scheme, perturbatively correct through NLO, in which there is no `rapidity subtraction'. That is, the NLO correction to the impact factor is not explicitly separated from the high-energy evolution. Our construction exploits the skeleton structure of the (NLO) Balitsky-Kovchegov equation, in which the first step of the evolution is explicitly singled out. The NLO impact factor is included by computing this first emission with the exact kinematics for the emitted gluon, rather than by using the eikonal approximation. This particular calculation has already been presented in the literature [1,2], but the reorganization of the perturbation theory that we propose is new. As compared to the proposal in [1,2], our scheme is free of the fine-tuning inherent in the rapidity subtraction, which might be the origin of the negativity of the NLO cross-section observed in previous studies.

   hep-phJHEP(2016)·84 citations
10. 10*

    NLO QCD off-shell effects for top pair production with a jet in the dilepton channel

    Manfred Kraus🇩🇪

    A short summary of a NLO QCD calculation for the top-quark pair production with a jet in the dilepton decay channel is presented. The calculation takes into account all double, single, non-resonant and interference contributions. Thus, NLO QCD corrections are computed for the process pp -> e+ ve mu- vm~ b b~ j + X. This calculation provides the first complete description, which overcomes the narrow width approximation for ttj process in the dilepton decay channel. Results for the total cross section and differential distributions for the LHC at sqrt(s) = 8 TeV are shown.

    hep-phPoS(2016)·4 citations
11. 11*

    331 Models and Grand Unification: From Minimal SU(5) to Minimal SU(6)

    Frank F. Deppisch🇬🇧 · Chandan Hati🇮🇳 · Sudhanwa Patra🇮🇳 · Utpal Sarkar🇮🇳 · Josè W.F. Valle🇪🇸

    We consider the possibility of grand unification of the $\mathrm{SU}(3{)}_{\mathrm{c}}\otimes \mathrm{SU}(3{)}_{\mathrm{L}}\otimes \mathrm{U}(1{)}_{\mathrm{X}}$ model in an SU(6) gauge unification group. Two possibilities arise. Unlike other conventional grand unified theories, in SU(6) one can embed the $\mathrm{SU}(3{)}_{\mathrm{c}}\otimes \mathrm{SU}(3{)}_{\mathrm{L}}\otimes \mathrm{U}(1{)}_{\mathrm{X}}$ model as a subgroup such that different multiplets appear with different multiplicities. Such a scenario may emerge from the flux breaking of the unified group in an E(6) F-theory GUT. This provides new ways of achieving gauge coupling unification in $\mathrm{SU}(3{)}_{\mathrm{c}}\otimes \mathrm{SU}(3{)}_{\mathrm{L}}\otimes \mathrm{U}(1{)}_{\mathrm{X}}$ models while providing the radiative origin of neutrino masses. Alternatively, a sequential variant of the $\mathrm{SU}(3{)}_{\mathrm{c}}\otimes \mathrm{SU}(3{)}_{\mathrm{L}}\otimes \mathrm{U}(1{)}_{\mathrm{X}}$ model can fit within a minimal SU(6) grand unification, which in turn can be a natural E(6) subgroup. This minimal SU(6) embedding does not require any bulk exotics to account for the chiral families while allowing for a TeV scale $\mathrm{SU}(3{)}_{\mathrm{c}}\otimes \mathrm{SU}(3{)}_{\mathrm{L}}\otimes \mathrm{U}(1{)}_{\mathrm{X}}$ model with seesaw-type neutrino masses.

    hep-phPLB(2016)·42 citations
12. 12*

    Fermion masses as mixing parameters in the SM

    U. J. Saldaña-Salazar🇲🇽

    Flavor transitions via the charged current interactions are parametrized by a three dimensional and unitary transformation. This so called mixing matrix requires of four mixing parameters. Here we show that under the phenomenological observation of hierarchical fermion masses, $m_3\gg m_2\gg m_1$, a mixing parametrization can be built with its mixing parameters being the corresponding four independent mass ratios of each fermion sector, i.e., $m_u/m_c$, $m_c/m_t$, $m_d/m_s$, and $m_s/m_b$ and $m_e/m_{\mu }$, $m_{\mu }/m_{\tau }$, $m_{\nu 1}/m_{\nu 2}$, and $m_{\nu 2}/m_{\nu 3}$, for the quark and lepton sector, respectively.

    hep-phJ.Phys.Conf.Ser.(2016)·2 citations
13. 13*

    Forbidden Dark Matter at the Weak Scale via the Top Portal

    Antonio Delgado🇺🇸 · Adam Martin🇺🇸 · Nirmal Raj🇺🇸

    At the tail of its velocity distribution, cold dark matter (DM) can annihilate at finite temperature to states heavier than itself. We explore the possibility that DM freezeout is dictated by these "forbidden annihilations" at the electroweak scale. Demanding that annihilation products be Standard Model particles, we find that for the forbidden mechanism to primarily set the DM relic abundance, DM must couple predominantly, if not solely, to top quarks. This can be arranged by invoking a non-trivial flavor structure such as Minimal Flavor Violation. We avail two avenues to achieve the correct thermal cross-section, requiring a mediator exchanged in the $s$- or $t$-channel. These simplified models submit easily to direct detection and collider searches, and necessarily hide from indirect detection signals. Viable supersymmetric spectra involving the forbidden mechanism may be found if combined with co-annihilation.

    hep-phPRD(2017)·31 citations
14. 14*

    Physical Angular Momentum Separation for QED

    Weimin Sun🇨🇳

    We study the non-uniqueness problem of the gauge-invariant angular momentum separation for the case of QED, which stems from the recent controversy concerning the proper definitions of the orbital angular momentum and spin operator of the individual parts of a gauge field system. For the free quantum electrodynamics without matter, we show that the basic requirement of Euclidean symmetry selects a unique physical angular momentum separation scheme from the multitude of the possible angular momentum separation schemes constructed using the various Gauge Invariant Extentions. Based on these results, we propose a set of natural angular momentum separation schemes for the case of interacting QED by invoking the formalism of asymptotic fields. Some perspectives on such a problem for the case of QCD are briefly discussed.

    hep-phMod.Phys.Lett.A(2017)·0 citations
15. 15*

    Nonperturbative quantization à la Heisenberg for non-Abelian gauge theories: two-equation approximation

    Vladimir Dzhunushaliev🇰🇿

    The nonperturbative quantization technique à la Heisenberg is applied for non-Abelian gauge theories. The operator Yang-Mills equation is written, which on the corresponding averaging gives an infinite set of equations for all Green functions. We split all degrees of freedom into two groups: in the former, we have $A_{\mu }^a\in \mathcal{G}\subset SU(N)$, and in the second group we have coset degrees of freedom $SU(N)/\mathcal{G}$. Using such splitting and some assumptions about 2- and 4-point Green functions, we truncate the infinite set of equations to two equations. The first equation is for the gauge fields from the subgroup $\mathcal{G}$, and the second equation is for a gluon condensate which is the dispersion of quantum fluctuations of the coset fields. Two examples are considered: The first one is a flux tube solution describing longitudinal color electric fields stretched between quark and antiquark located at the $\pm$ infinities. The second one is a flux tube stretched between two quarks (antiquarks) located at $\pm \infty$. A special case is considered when the longitudinal electric field produced by a quark located at $+\infty$ is equal and oppositely directed to the field generated by a quark located at $-\infty$ that leads to zero total electric field. Both solutions represents the dual Meissner effect: the electric field is pushed out from the gluon condensate.

    hep-phEPJ Web Conf.(2017)·5 citations
16. 16*

    A novel probe of chiral restoration in nuclear medium

    Philipp Gubler🇰🇷 · Teiji Kunihiro🇯🇵 · Su Houng Lee🇰🇷

    We propose measuring the mass shift and width broadening of the $f_1(1285)$ meson together with those of the $\omega$ from a nuclear target as a means to experimentally probe the partial restoration of chiral symmetry inside the nuclear matter. The relation between the order parameter of chiral symmetry and the difference in the correlation functions of the $f_1(1285)$ current and the $\omega$ current is discussed in the limit where the disconnected diagrams are neglected. A QCD sum rule analysis of the $f_1(1285)$ meson mass leads to about 100 MeV attraction in nuclear matter, which can be probed in future experiments.

    ↳ nucl-thhep-phnucl-exPLB(2017)·22 citations
17. 17*

    Maximal isospin few-body systems of nucleons and $\Xi$ hyperons

    H. Garcilazo🇲🇽 · A. Valcarce🇪🇸 · J. Vijande🇪🇸

    By using local central Yukawa-type interactions that reproduce the low-energy parameters of the latest updates of the Nijmegen ESC08c potentials we show that the $N\Xi$, $NN\Xi$, $N\Xi \Xi$ and $NN\Xi \Xi$ systems with maximal isospin are bound. Since in these states the strong decay $N\Xi \to \Lambda \Lambda$ is forbidden by isospin conservation, these strange few-body systems will be stable under the strong interaction. These results may suggest that other states with different number of $N$'s and $\Xi$'s in the maximal isospin channel could also be bound.

    ↳ nucl-thhep-phPRC(2016)·24 citations
18. 18*

    Color-factor symmetry and BCJ relations for QCD amplitudes

    Robert W. Brown🇺🇸 · Stephen G. Naculich🇺🇸

    Tree-level $n$-point gauge-theory amplitudes with $n-2k$ gluons and $k$ pairs of (massless or massive) particles in the fundamental (or other) representation of the gauge group are invariant under a set of symmetries that act as momentum-dependent shifts on the color factors in the cubic decomposition of the amplitude. These symmetries lead to gauge-invariant constraints on the kinematic numerators. They also directly imply the BCJ relations among the Melia-basis primitive amplitudes previously obtained by Johansson and Ochirov.

    ↳ hep-thhep-phJHEP(2016)·24 citations
19. 19*

    Correlations of flow harmonics in 2.76A TeV Pb--Pb collisions

    Xiangrong Zhu🇨🇳 · You Zhou🇩🇰 · Haojie Xu🇨🇳 · Huichao Song🇨🇳

    Using the event-by-event viscous hydrodynamics VISH2+1 with MC-Glauber, MC-KLN, and AMPT initial conditions, we investigate the correlations of flow harmonics, including the symmetric cumulants $S{C}^v(m,n)$, the normalized symmetric cumulants $NSC(m,n)$, and the Pearson correlation coefficients $C(v_m^2,v_n^2)$ in 2.76A TeV Pb--Pb collisions. We find $S{C}^v(m,n)$ is sensitive to both initial conditions and the specific shear viscosity $\eta /s$. A comparison with the recent ALICE data show that our hydrodynamic calculations can qualitatively describe the data of $S{C}^v(3,2)$ and $S{C}^v(4,2)$ for various initial conditions, which demonstrate that $v_2$, $v_4$ are correlated and $v_2$, $v_3$ are anti-correlated. Meanwhile, the predicted symmetric cumulants $S{C}^v(5,2)$, $S{C}^v(5,3)$, and $S{C}^v(4,3)$ reveal that $v_2$ and $v_5$, $v_3$ and $v_5$ are correlated, $v_3$ and $v_4$ are anti-correlated in most centrality classes. We also find $NS{C}^v(3,2)$ and $C(v_3^2,v_2^2)$, which are insensitive to $\eta /s$, are mainly determined by corresponding $NS{C}^{\epsilon }(3,2)$ and $C({\epsilon }_3^2,{\epsilon }_2^2)$ correlators from the initial state. In contrast, other $NS{C}^v(m,n)$ and $C(v_m^2,v_n^2)$ correlators are influenced by both initial conditions and $\eta /s$, which illustrates the non-linear mode couplings in higher flow harmonics with $n\ge 4$.

    ↳ nucl-thhep-phnucl-exPRC(2017)·68 citations
20. 20*

    Two-loop scale-invariant scalar potential and quantum effective operators

    D. M. Ghilencea🇷🇴 · Z. Lalak🇵🇱 · P. Olszewski🇵🇱

    Spontaneous breaking of quantum scale invariance may provide a solution to the hierarchy and cosmological constant problems. In a scale-invariant regularization, we compute the two-loop potential of a higgs-like scalar $\varphi$ in theories in which scale symmetry is broken only spontaneously by the dilaton ($\sigma$). Its vev $⟨\sigma ⟩$ generates the DR subtraction scale ($\mu \sim ⟨\sigma ⟩$), which avoids the explicit scale symmetry breaking by traditional regularizations (where $\mu$=fixed scale). The two-loop potential contains effective operators of non-polynomial nature as well as new corrections, beyond those obtained with explicit breaking ($\mu$=fixed scale). These operators have the form: ${\varphi }^6/{\sigma }^2$, ${\varphi }^8/{\sigma }^4$, etc, which generate an infinite series of higher dimensional polynomial operators upon expansion about $⟨\sigma ⟩\gg ⟨\varphi ⟩$, where such hierarchy is arranged by {\it one} initial, classical tuning. These operators emerge at the quantum level from evanescent interactions ($\propto ϵ$) between $\sigma$ and $\varphi$ that vanish in $d=4$ but are demanded by classical scale invariance in $d=4-2ϵ$. The Callan-Symanzik equation of the two-loop potential is respected and the two-loop beta functions of the couplings differ from those of the same theory regularized with $\mu =$fixed scale. Therefore the running of the couplings enables one to distinguish between spontaneous and explicit scale symmetry breaking.

    ↳ hep-thhep-phEPJC(2016)·53 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.