Mon·Jan 18, 2016Monday·January 18, 2016

1. 01*

   Higgs + Multi-jets in Gluon Fusion

   Nicolas Greiner🇨🇭 · Stefan Hoeche🇺🇸 · Gionata Luisoni🇨🇭 · Marek Schonherr🇨🇭 · Jan-Christopher Winter🇺🇸 · Valery Yundin🇩🇪

   We present a detailed phenomenological analysis of the production of a Standard Model Higgs boson in association with up to three jets. The Higgs is produced via gluon fusion, which is an irreducible background to the vector boson fusion mechanism. We calculate the next-to-leading order corrections in QCD in the limit of an infinitely heavy top quark. Numerical results are presented for a large variety of observables, for different selection cuts, and for different choices of the jet tagging scheme.

   hep-phPoS(2016)·3 citations
2. 02*

   Hints for leptonic CP violation or New Physics?

   David V. Forero🇺🇸 · Patrick Huber🇺🇸

   One of the major open questions in the neutrino sector is the issue of leptonic CP violation. Current global oscillation data shows a mild preference for a large, potentially maximal value for the Dirac CP phase in the neutrino mixing matrix. In this letter, we point out that New Physics in the form of neutral-current like non-standard interactions with real couplings would likely yield a similar conclusion even if CP in the neutrino sector were conserved. Therefore, the claim for a discovery of leptonic CP violation will require a robust ability to test New Physics scenarios.

   hep-phhep-exPRL(2016)·75 citations
3. 03*

   New signatures and limits on R-parity violation from resonant squark production

   Angelo Monteux (Rutgers University)🇺🇸

   We discuss resonant squark production at the LHC via baryonic $R$-parity violating interactions. The cross section easily exceeds pair-production and a new set of signatures can be used to probe squarks, particularly stops. These include dijet resonances, same-sign top quarks and four-jet resonances with large $b$-jet multiplicities, as well as the possibility of displaced neutralino decays. We use publicly available searches at $\sqrt{s}=8$ TeV and first results from collisions at $\sqrt{s}=13$ TeV to set upper limits on $R$-parity violating couplings, with particular focus on simplified models with light stops and neutralinos. The exclusion reach of these signatures is comparable to $R$-parity-conserving searches, $m_{\tilde{t}}\simeq 500-700$ GeV. In addition, we find that O(1) couplings involving the stop can be excluded well into the multi-TeV range, and stress that new searches for single- and pair-produced four-jet resonances will be necessary to exclude sub-TeV stops for a natural SUSY spectrum with light higgsinos.

   hep-phhep-exJHEP(2016)·25 citations
4. 04*

   Transport coefficients of heavy baryons

   Laura Tolos🇪🇸 · Juan M. Torres-Rincon🇫🇷 · Santosh K. Das🇮🇹

   We compute the transport coefficients (drag and momentum diffusion) of the low-lying heavy baryons ${\Lambda }_c$ and ${\Lambda }_b$ in a medium of light mesons formed at the later stages of high-energy heavy-ion collisions. We employ the Fokker-Planck approach to obtain the transport coefficients from unitarized baryon-meson interactions based on effective field theories that respect chiral and heavy-quark symmetries. We provide the transport coefficients as a function of temperature and heavy-baryon momentum, and analyze the applicability of certain nonrelativistic estimates. Moreover we compare our outcome for the spatial diffusion coefficient to the one coming from the solution of the Boltzmann-Uehling-Uhlenbeck transport equation and we find a very good agreement between both calculations. The transport coefficients for ${\Lambda }_c$ and ${\Lambda }_b$ in a thermal bath will be used in a subsequent publication as input in a Langevin evolution code for the generation and propagation of heavy particles in heavy-ion collisions at LHC and RHIC energies.

   hep-phnucl-thPRD(2016)·22 citations
5. 05*

   Four-loop relation between the $\overline{\mathrm{MS}}$ and on-shell quark mass

   Peter Marquard🇩🇪 · Alexander V. Smirnov🇷🇺 · Vladimir A. Smirnov🇷🇺 · Matthias Steinhauser🇩🇪

   In this contribution we discuss the four-loop relation between the on-shell and $\overline{\mathrm{MS}}$ definition of heavy quark masses which is applied to the top, bottom and charm case. We also present relations between the $\overline{\mathrm{MS}}$ quark mass and various threshold mass definitions and discuss the uncertainty at next-to-next-to-next-to-leading order.

   hep-phPoS(2016)·4 citations
6. 06*

   A Pati-Salam Version of Subcritical Hybrid Inflation

   B. Charles Bryant🇺🇸 · Stuart Raby🇺🇸

   In this paper we present a model of subcritical hybrid inflation with a Pati-Salam [PS] symmetry group. Both the inflaton and waterfall fields contribute to the necessary e-foldings of inflation, while only the waterfall field spontaneously breaks PS hence monopoles produced during inflation are diluted during the inflationary epoch. The model is able to produce a tensor-to-scalar ratio, $r<0.09$ consistent with the latest BICEP2/Keck and Planck data, as well as scalar density perturbations and spectral index, $n_s$, consistent with Planck data. For particular values of the parameters, we find $r=0.084$ and $n_s=0.0963$. The energy density during inflation is directly related to the PS breaking scale, $v_{PS}$. The model also incorporates a ${\mathbb{Z}}_4^R$ symmetry which can resolve the $\mu$ problem and suppress dimension 5 operators for proton decay, leaving over an exact $R$-parity. Finally the model allows for a complete three family extension with a $D_4$ family symmetry which reproduces low energy precision electroweak and LHC data.

   hep-phPRD(2016)·16 citations
7. 07*

   The photon PDF in events with rapidity gaps

   L. A. Harland-Lang🇬🇧 · V. A. Khoze🇬🇧 · M. G. Ryskin🇷🇺

   We consider photon-initiated events with large rapidity gaps in proton-proton collisions, where one or both protons may break up. We formulate a modified photon PDF that accounts for the specific experimental rapidity gap veto, and demonstrate how the soft survival probability for these gaps may be implemented consistently. Finally, we present some phenomenological results for the two-photon induced production of lepton and $W$ boson pairs.

   hep-phEPJC(2016)·89 citations
8. 08*

   Factorization and angular distribution asymmetries in charmful baryonic B decays

   Y.K. Hsiao🇨🇳 · C.Q. Geng🇨🇳

   We examine the validity of the generalized factorization method and calculate the angular correlations in the charmful three-body baryonic decays of ${\bar{B}}^0\to \Lambda \bar{p}{D}^{(\ast )+}$. With the timelike baryonic form factors newly extracted from the measured baryonic $B$ decays, we obtain $\mathcal{B}({\bar{B}}^0\to \Lambda \bar{p}{D}^{+},\Lambda \bar{p}{D}^{\ast +})=(1.85\pm 0.30,2.75\pm 0.24)\times 10^{-5}$ to agree with the recent data from the BELLE Collaboration, which demonstrates that the theoretical approach based on the factorization still works well. For the angular distribution asymmetries, we find ${\mathcal{A}}_{\theta }({\bar{B}}^0\to \Lambda \bar{p}{D}^{+},\Lambda \bar{p}{D}^{\ast +})=(-0.030\pm 0.002,+0.150\pm 0.000)$, which are consistent with the current measurements. Moreover, we predict that ${\mathcal{A}}_{\theta }({\bar{B}}^0\to p\bar{p}{D}^0,p\bar{p}{D}^{\ast 0})=+0.04\pm 0.01$. Future precise explorations of these angular correlations at BELLE and LHCb as well as super-BELLE are important to justify the present factorization approach in the charmful three-body baryonic decays.

   hep-phhep-exPRD(2016)·15 citations
9. 09*

   Strong $Z_c^{+}(3900)\to J/\psi {\pi }^{+};{\eta }_c{\rho }^{+}$ decays in QCD

   S. S. Agaev🇦🇿 · K. Azizi🇹🇷 · H. Sundu🇹🇷

   The widths of the strong decays $Z_c^{+}(3900)\to J/\psi {\pi }^{+}$ and $Z_c^{+}(3900)\to {\eta }_c{\rho }^{+}$ are calculated. To this end, the mass and decay constant of the exotic $Z_c^{+}(3900)$ state are computed by means of a two-point sum rule. The obtained results are then used to calculate the strong couplings $g_{Z_{c}J/\psi \pi }$ and $g_{Z_c{\eta }_c\rho }$ employing QCD sum rules on the light-cone supplied by a technique of the soft-meson approximation. We compare our predictions on the mass and decay widths with available experimental data and other theoretical results.

   hep-phPRD(2016)·89 citations
10. 10*

    How to retrieve additional information from the multiplicity distributions

    Grzegorz Wilk🇵🇱 · Zbigniew Włodarczyk🇵🇱

    Multiplicity distributions $P(N)$ measured in multiparticle production processes are most frequently described by the Negative Binomial Distribution (NBD). However, with increasing collision energy some systematic discrepancies become more and more apparent. They are usually attributed to the possible multi-source structure of the production process and described using a multi-NBD form of the multiplicity distribution. We investigate the possibility of keeping a single NBD but with its parameters depending on the multiplicity $N$. This is done by modifying the widely known clan model of particle production leading to the NBD form of $P(N)$. This is then confronted with the approach based on the so-called cascade-stochastic formalism which is based on different types of recurrence relations defining $P(N)$. We demonstrate that a combination of both approaches allows the retrieval of additional valuable information from the multiplicity distributions, namely the oscillatory behavior of the counting statistics apparently visible in the high energy data.

    hep-phnucl-thJ.Phys.G(2017)·24 citations
11. 11*

    Partners of the $X(3872)$ and HQSS breaking

    D.R. Entem🇪🇸 · P.G. Ortega🇨🇭 · F. Fernandez🇪🇸

    Since the discovery of the $X(3872)$ the study of heavy meson molecules has been the subject of many investigations. On the experimental side different experiments have looked for its spin partners and the bottom analogs. On the theoretical side different approaches have been used to understand this state. Some of them are EFT that impose HQSS and so they make predictions for the partners of the $X(3872)$, suggesting the existence of a $J^{PC}=2^{++}$ partner in the charm sector or $J^{PC}=1^{++}$ or $2^{++}$ analogs in the bottom. In our work, in order to understand the $X(3872)$, we use a Chiral quark model in which, due to the proximity to the $D{D}^{\ast }$ threshold, we include $c\bar{c}$ states coupled to $D{D}^{\ast }$ molecular components. In this coupled channel model the relative position of the bare $c\bar{c}$ states with two meson thresholds are very important. We have looked for the $X(3872)$ partners and we don't find a bound state in the $D^{\ast }{D}^{\ast }$ $J^{PC}=2^{++}$. In the bottom sector we find the opposite situation where the $B^{\ast }{B}^{\ast }$ with $J^{PC}=2^{++}$ is bounded while the $J^{PC}=1^{++}$ is not bounded. These results shows how the coupling with $c\bar{c}$ states can induced different results than those expected by HQSS. The reason is that this symmetry is worse in the open heavy meson sector than in the hidden heavy meson sector.

    hep-phAIP Conf.Proc.(2016)·9 citations
12. 12*

    Pulsar timing signal from ultralight axion in $f(R)$ theory

    Arata Aoki🇯🇵 · Jiro Soda🇯🇵

    An ultralight axion around $10^{-23}$ eV is known as a viable dark matter candidate. A distinguished feature of such a dark matter is the oscillating pressure which produces the oscillation of the gravitational potential with frequency in the nano-Hz range. Recently, Khmelnitsky and Rubakov pointed out that this time dependent potential induces the pulse arrival residual and could be observed by the Square Kilometre Array (SKA) experiment. In this paper, we study the detectability of the oscillating pressure of the axion in the framework of $f(R)$ theory, and show that the amplitude of the gravitational potential can be enhanced or suppressed compared to that in Einstein's theory depending on the parameters of the $f(R)$ model and mass of the axion. In particular, we investigate the Hu-Sawicki model and find the condition that the Hu-Sawicki model is excluded.

    hep-phastro-ph.COgr-qcPRD(2016)·22 citations
13. 13*

    Weak decays of heavy hadrons into dynamically generated resonances

    Eulogio Oset🇪🇸 · Wei-Hong Liang🇨🇳 · Melahat Bayar🇹🇷 · Ju-Jun Xie🇨🇳 · Lian Rong Dai🇨🇳 · Miguel Albaladejo🇪🇸 · Marina Nielsen🇧🇷 · Takayasu Sekihara🇯🇵 · Fernando Navarra🇧🇷 · Luis Roca🇪🇸 · Maxim Mai🇩🇪 · Juan Nieves🇪🇸 and 15 other authors

    In this review we give a perspective of the theoretical work done recently on the interpretation of results from $B$, $D$, ${\Lambda }_b$, ${\Lambda }_c$ weak decays into final states that contain interacting hadrons, and how it is possible to obtain additional valuable information that is increasing our understanding of hadron interactions and the nature of many hadronic resonances. The novelty of these processes is that one begins with a clean picture at the quark level which allows one to select the basic mechanisms by means of which the process proceeds. Finally, one has a final state described in terms of quarks. To make contact with the experiments, where mesons and baryons are observed, one must hadronize, creating pairs of $q\bar{q}$ and writing the new states in terms of mesons and baryons. This concludes the primary hadron production in these processes. After that, the interaction of these hadrons takes place, offering a rich spectrum of resonances and special features from where it is possible to learn much about the interaction of these hadrons and the nature of many resonances in terms of the components of their wave functions.

    hep-phnucl-thIJMPE(2016)·160 citations
14. 14*

    Flavor Changing Leptonic Decays of Heavy Higgs Bosons

    Marc Sher🇺🇸 · Keith Thrasher🇺🇸

    CMS has reported indications (2.4\sigma) of the decay of the Higgs boson into \mu\tau. The simplest explanation for such a decay would be a general Two Higgs Doublet Model (2HDM). In this case, one would expect the heavy neutral Higgs bosons, H and A, to also decay in a similar manner. We study two specific models. The first is the type III 2HDM, and the second is a 2HDM, originally proposed by Branco et al., in which all flavor-changing neutral processes are given by the weak mixing matrix. In the latter model, since mixing between the second and third generations in the lepton sector is large, flavor-changing interactions are large. In this model it is found that the decays of H and A to \mu\tau can be as high as 60 percent. This work has nothing to do with the 750 GeV diphoton resonance.

    hep-phPRD(2016)·41 citations
15. 15*

    Calculation of Multi-Loop Integrals with SecDec-3.0

    Johannes Schlenk🇩🇪 · Tom Zirke🇩🇪

    In this contribution we discuss new features of SecDec-3.0, a public program for the evaluation of dimensionally-regulated parametric integrals using sector decomposition. We will focus on two main aspects: the implementation of an improved geometric decomposition algorithm and the recently added support for complex masses.

    hep-phPoS(2016)·10 citations
16. 16*

    Predictions on the second-class current decays ${\tau }^{-}\to {\pi }^{-}{\eta }^{(\prime )}{\nu }_{\tau }$

    Rafel Escribano🇪🇸 · Sergi Gonzalez-Solis🇪🇸 · Pablo Roig🇲🇽

    We analyze the second-class current decays ${\tau }^{-}\to {\pi }^{-}{\eta }^{(\prime )}{\nu }_{\tau }$ in the framework of Chiral Perturbation Theory with resonances. Taking into account ${\pi }^0$-$\eta$-${\eta }^{\prime }$ mixing, the ${\pi }^{-}{\eta }^{(\prime )}$ vector form factor is extracted, in a model-independent way, using existing data on the ${\pi }^{-}{\pi }^0$ one. For the participant scalar form factor, we have considered different parameterizations ordered according to their increasing fulfillment of analyticity and unitarity constraints. We start with a Breit-Wigner parameterization dominated by the $a_0(980)$ scalar resonance and after we include its excited state, the $a_0(1450)$. We follow by an elastic dispersion relation representation through the Omnès integral. Then, we illustrate a method to derive a closed-form expression for the ${\pi }^{-}\eta$, ${\pi }^{-}{\eta }^{\prime }$ (and $K^{-}{K}^0$) scalar form factors in a coupled-channels treatment. Finally, predictions for the branching ratios and spectra are discussed emphasizing the error analysis. An interesting result of this study is that both ${\tau }^{-}\to {\pi }^{-}{\eta }^{(\prime )}{\nu }_{\tau }$ decay channels are promising for the soon discovery of second-class currents at Belle-II. We also predict the relevant observables for the partner ${\eta }_{\ell 3}^{(\prime )}$ decays, which are extremely suppressed in the Standard Model.

    hep-phhep-exPRD(2016)·80 citations
17. 17*

    Automating Predictions for Standard Model Effective Field Theory in MadGraph5_aMC@NLO

    Cen Zhang🇺🇸

    Next-to-leading order event generation for the Standard Model effective field theory has started to become available in the MadGraph5_aMC@NLO framework. In this talk we discuss some of the recent progresses in this direction, with a focus on the top-quark sector.

    hep-phhep-exPoS(2016)·7 citations
18. 18*

    Schwinger-Dyson approach and its application to generate a light composite scalar

    A. Doff🇧🇷 · A. A. Natale🇧🇷

    We discuss the possibility of generating a light composite scalar boson, in a scenario that we may generically call Technicolor, or in any variation of a strongly interacting theory, where by light we mean a scalar composite mass about one order of magnitude below the characteristic scale of the strong theory. Instead of most of the studies about a composite Higgs boson, which are based on effective Lagrangians, we consider this problem in the framework of non-perturbative solutions of the fermionic Schwinger-Dyson and Bethe-Salpeter equations. We study a range of mechanisms proposed during the recent years to form such light composite boson, and verify that such possibility seems to be necessarily associated to a fermionic self-energy that decreases slowly with the momentum.

    hep-phInt.J.Mod.Phys.A(2016)·7 citations
19. 19*

    Sensitivity of the COSY Dibaryon Candidate to np Elastic Scattering Measurements

    R.L. Workman🇺🇸 · W.J. Briscoe🇺🇸 · I.I. Strakovsky (GWU)🇺🇸

    The case for a dibaryon resonance, appearing in np scattering, has support from a WASA-at-COSY measurement of the polarization quantity A_y over a center-of-mass energy region suggested by structures seen earlier in two-pion production experiments. Here we compare fits with and without an associated pole in order to clarify the impact of these COSY data. We then consider what further np scattering measurements would most clearly distinguish between the pole and non-pole fit results.

    ↳ nucl-thhep-exhep-phnucl-exPRC(2016)·20 citations
20. 20*

    Gravitational Black Hole Hair from Event Horizon Supertranslations

    Artem Averin🇩🇪 · Gia Dvali🇩🇪 · Cesar Gomez🇪🇸 · Dieter Lust🇩🇪

    We discuss BMS supertranslations both at null-infinity and on the horizon for the case of the Schwarzschild black hole. We show that both kinds of supertranslations lead to infinetly many gapless physical excitations. On this basis we construct a quotient algebra using suited superpositions of both kinds of transformations which cannot be compensated by an ordinary BMS-supertranslation and therefore are intrinsically due to the presence of an event horizon. We show that these quotient transformations are physical and generate gapless excitations on the horizon that can account for the gravitational hair as well as for the black hole entropy. We identify the physics of these modes as associated with Bogolioubov-Goldstone modes due to quantum criticality. Classically the number of these gapless modes is infinite. However, we show that due to quantum criticality the actual amount of information-carriers becomes finite and consistent with Bekenstein entropy. Although we only consider the case of Schwarzschild geometry, the arguments are extendable to arbitrary space-times containing event horizons.

    ↳ hep-thgr-qchep-phJHEP(2016)·83 citations
21. 21*

    Research infrastructures in the LHC era: a scientometric approach

    Stefano Carrazza🇨🇭 · Alfio Ferrara🇮🇹 · Silvia Salini🇮🇹

    When a research infrastructure is funded and implemented, new information and new publications are created. This new information is the measurable output of discovery process. In this paper, we describe the impact of infrastructure for physics experiments in terms of publications and citations. In particular, we consider the Large Hadron Collider (LHC) experiments (ATLAS, CMS, ALICE, LHCb) and compare them to the Large Electron Positron Collider (LEP) experiments (ALEPH, DELPHI, L3, OPAL) and the Tevatron experiments (CDF, D0). We provide an overview of the scientific output of these projects over time and highlight the role played by remarkable project results in the publication-citation distribution trends. The methodological and technical contribution of this work provides a starting point for the development of a theoretical model of modern scientific knowledge propagation over time.

    ↳ physics.soc-phcs.DLhep-exhep-phTechnol.Forecast.Soc.Chang.(2016)·3 citations
22. 22*

    Chiral Charge Erasure via Thermal Fluctuations of Magnetic Helicity

    Andrew J. Long🇺🇸 · Eray Sabancilar🇨🇭

    We consider a relativistic plasma of fermions coupled to an Abelian gauge field and carrying a chiral charge asymmetry, which might arise in the early Universe through baryogenesis. It is known that on large length scales, $\lambda \gtrsim 1/(\alpha {\mu }_5)$, the chiral anomaly opens an instability toward the erasure of chiral charge and growth of magnetic helicity. Here the chemical potential ${\mu }_5$ parametrizes the chiral asymmetry and $\alpha$ is the fine-structure constant. We study the process of chiral charge erasure through the thermal fluctuations of magnetic helicity and contrast with the well-studied phenomenon of Chern-Simons number diffusion. Through the fluctuation-dissipation theorem we estimate the amplitude and time scale of helicity fluctuations on the length scale $\lambda$, finding $\delta \mathcal{H}\sim \lambda T$ and $\tau \sim \alpha {\lambda }^3{T}^2$ for a relativistic plasma at temperature $T$. We argue that the presence of a chiral asymmetry allows the helicity to grow diffusively for a time $t\sim T^3/({\alpha }^5{\mu }_5^4)$ until it reaches an equilibrium value $\mathcal{H}\sim {\mu }_5{T}^2/\alpha$, and the chiral asymmetry is partially erased. If the chiral asymmetry is small, ${\mu }_5<T/\alpha$, this avenue for chiral charge erasure is found to be slower than the chiral magnetic effect for which $t\sim T/({\alpha }^3{\mu }_5^2)$. This mechanism for chiral charge erasure can be important for the hypercharge sector of the Standard Model as well as extensions including $\mathrm{U}(1)$ gauge interactions, such as asymmetric dark matter models.

    ↳ hep-thastro-ph.COhep-phJCAP(2016)·22 citations
23. 23*

    The String BCJ Relations Revisited and Extended Recurrence relations of Nonrelativistic String Scattering Amplitudes

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

    We review and extend high energy string BCJ relations in both the fixed angle and Regge regimes. We then give an explicit proof of four point string BCJ relations for all energy. This calculation provides an alternative proof of the one based on monodromy of integration in string amplitude calculation. In addition, we calculate both s-t and t-u channel nonrelativistic low energy string scattering amplitudes of three tachyons and one leading trojectory string state at arbitrary mass levels. We discover that the mass and spin dependent nonrelativistic string BCJ relations can be expressed in terms of Gauss hypergeometry functions. As an application, for each fixed mass level N, we derive extended recurrence relations among nonrelativistic low energy string scattering amplitudes of string states with different spins and different channels.

    ↳ hep-thhep-phJHEP(2016)·10 citations
24. 24*

    Precision Electroweak measurements at the FCC-ee

    Mogens Dam🇩🇰

    Because of a luminosity of up to five orders of magnitude larger than at LEP, electroweak precision measurements at the FCC-ee -- the Future Circular Collider with electron-positron beams -- would provide improvements by orders of magnitude over the present status and constitute a broad search for the existence of new, weakly interacting particles up to very high energy scales. The FCC-ee will address centre-of-mass energies ranging from below the Z pole to the $\mathrm{t}\bar{\mathrm{t}}$ threshold and above. At energies around the Z pole, the Z-boson mass and width can be measured to better than 100 keV each. Asymmetry measurements at the Z pole allow improvements in the determination of the weak mixing angle by at least a factor 30 to $\delta {\sin }^2\theta {}_{\mathrm{W}}^{\mathrm{eff}}\simeq 6\times 10^{-6}$. A determination of the electromagnetic coupling constant at the Z energy scale, ${\alpha }_{\mathrm{QED}}(m_{\mathrm{Z}}^2)$, to a relative precision of $3\times 10^{-5}$ can be obtained via measurement of the forward-backward asymmetry of lepton pairs at two energy points $\pm 3.2\text{GeV}$ away from the Z peak. At energies around the WW threshold, high-statistic cross section measurements can provide a determination of the W mass to 300 keV. The key breakthrough advantage of the FCC-ee in these achievements, beside the large luminosity, is the possibility of a continous, precise determination of the beam energy by resonant depolarization at the Z peak and at the WW threshold. Precise measurements of the hadronic branching fractions of the Z and W bosons allow for considerably improvements in the determination of the strong coupling constant down to a precision of $\delta {\alpha }_{\mathrm{s}}(m_{\mathrm{Z}}^2)\simeq 0.0001$. An energy scan around the 350 GeV $\mathrm{t}\bar{\mathrm{t}}$ threshold allows a 10 MeV measurement of the top-quark mass.

    ↳ hep-exhep-phPoS(2015)·10 citations
25. 25*

    What can we learn from the directed flow in heavy-ion collisions at BES RHIC energies?

    Yu. B. Ivanov🇷🇺 · A. A. Soldatov🇷🇺

    Analysis of directed flow ($v_1$) of protons, antiprotons and pions in heavy-ion collisions is performed in the range of collision energies $\sqrt{s_{NN}}$ = 2.7--39 GeV. Simulations have been done within a three-fluid model employing a purely hadronic equation of state (EoS) and two versions of the EoS with deconfinement transitions: a first-order phase transition and a smooth crossover transition. The crossover EoS is unambiguously preferable for the description of the most part of experimental data in this energy range. The directed flow indicates that the crossover deconfinement transition takes place in semicentral Au+Au collisions in a wide range of collision energies 4 \lsim\sqrt{s_{NN}}\lsim$ 30 GeV. The obtained results suggest that the deconfinement EoS's in the quark-gluon sector should be stiffer at high baryon densities than those used in the calculation. The latter finding is in agreement with that discussed in astrophysics.

    ↳ nucl-thhep-phnucl-exEPJA(2016)·35 citations
26. 26*

    Quantum and thermal fluctuations in quantum mechanics and field theories from a new version of semiclassical theory

    M.A. Escobar-Ruiz🇲🇽 · E. Shuryak🇺🇸 · A.V. Turbiner🇺🇸

    We develop a new semiclassical approach, which starts with the density matrix given by the Euclidean time path integral with fixed coinciding endpoints, and proceed by identifying classical (minimal Euclidean action) path, to be referred to as {\it flucton}, which passes through this endpoint. Fluctuations around flucton path are included, by standard Feynman diagrams, previously developed for instantons. We calculate the Green function and evaluate the one loop determinant both by direct diagonalization of the fluctuation equation, and also via the trick with the Green functions. The two-loop corrections are evaluated by explicit Feynman diagrams, and some curious cancellation of logarithmic and polylog terms is observed. The results are fully consistent with large-distance asymptotics obtained in quantum mechanics. Two classic examples -- quartic double-well and sine-Gordon potentials -- are discussed in detail, while power-like potential and quartic anharmonic oscillator are discussed in brief. Unlike other semiclassical methods, like WKB, we do not use the Schrödinger equation, and all the steps generalize to multi-dimensional or quantum fields cases straightforwardly.

    ↳ hep-thhep-phPRD(2016)·17 citations
27. 27*

    Initial conditions from the shadowed Glauber model for Pb+Pb at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV

    Snigdha Ghosh🇮🇳 · Sushant K. Singh🇮🇳 · Sandeep Chatterjee🇮🇳 · Jane Alam🇮🇳 · Sourav Sarkar🇮🇳

    We study the initial conditions for Pb+Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2.76$ TeV using the two component Monte-Carlo Glauber model with shadowing of the nucleons in the interior by the leading ones. The model parameters are fixed by comparing to the multiplicity data of p+Pb and Pb+Pb at $\sqrt{s_{\mathrm{NN}}}=5.02$ and $2.76$ TeV respectively. We then compute the centrality dependence of the eccentricities upto the fourth order as well as their event by event distributions. The inclusion of shadowing brings the Monte-Carlo Glauber model predictions in agreement with data as well as with results from other dynamical models of initial conditions based on gluon saturation at high energy nuclear collisions. Further, we find that the shadowed Glauber model provides the desired relative magnitude between the ellipticity and triangularity of the initial energy distribution required to explain the data on the even and odd flow harmonics $v_2$ and $v_3$ respectively at the LHC.

    ↳ nucl-thhep-phnucl-exPRC(2016)·14 citations
28. 28*

    Strongly interacting dynamics and the search for new physics at the LHC

    Thomas Appelquist🇺🇸 · Richard C. Brower🇺🇸 · George T. Fleming🇺🇸 · Anna Hasenfratz🇺🇸 · Xiao-Yong Jin🇺🇸 · Joe Kiskis🇺🇸 · Ethan T. Neil🇺🇸 · James C. Osborn🇺🇸 · Claudio Rebbi🇺🇸 · Enrico Rinaldi🇺🇸 · David Schaich🇺🇸 · Pavlos Vranas🇺🇸 · Evan Weinberg🇺🇸 · Oliver Witzel🇬🇧

    We present results for the spectrum of a strongly interacting SU(3) gauge theory with $N_f=8$ light fermions in the fundamental representation. Carrying out non-perturbative lattice calculations at the lightest masses and largest volumes considered to date, we confirm the existence of a remarkably light singlet scalar particle. We explore the rich resonance spectrum of the 8-flavor theory in the context of the search for new physics beyond the standard model at the Large Hadron Collider (LHC). Connecting our results to models of dynamical electroweak symmetry breaking, we estimate the vector resonance mass to be about 2 TeV with a width of roughly 450 GeV, and predict additional resonances with masses below ~3 TeV.

    ↳ hep-lathep-phPRD(2016)·159 citations
29. 29*

    Quark matter nucleation in neutron stars and astrophysical implications

    Ignazio Bombaci🇮🇹 · Domenico Logoteta🇮🇹 · Isaac Vidana🇵🇹 · Constanca Providencia🇵🇹

    A phase of strong interacting matter with deconfined quarks is expected in the core of massive neutron stars. We investigate the quark deconfinement phase transition in cold (T = 0) and hot beta-stable hadronic matter. Assuming a first order phase transition, we calculate and compare the nucleation rate and the nucleation time due to quantum and thermal nucleation mechanisms. We show that above a threshold value of the central pressure a pure hadronic star (HS) (i.e. a compact star with no fraction of deconfined quark matter) is metastable to the conversion to a quark star (QS) (i.e. a hybrid star or a strange star). This process liberates an enormous amount of energy, of the order of 10^{53}~erg, which causes a powerful neutrino burst, likely accompanied by intense gravitational waves emission, and possibly by a second delayed (with respect to the supernova explosion forming the HS) explosion which could be the energy source of a powerful gamma-ray burst (GRB). This stellar conversion process populates the QS branch of compact stars, thus one has in the Universe two coexisting families of compact stars: pure hadronic stars and quark stars. We introduce the concept of critical mass M_{cr} for cold HSs and proto-hadronic stars (PHSs), and the concept of limiting conversion temperature for PHSs. We show that PHSs with a mass M < M_{cr} could survive the early stages of their evolution without decaying to QSs. Finally, we discuss the possible evolutionary paths of proto-hadronic stars.

    ↳ astro-ph.HEastro-ph.SRhep-phnucl-thEPJA(2016)·83 citations

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