Fri·Aug 12, 2016Friday·August 12, 2016

1. 01*

   Flavor Cosmology: Dynamical Yukawas in the Froggatt-Nielsen Mechanism

   Iason Baldes🇩🇪 · Thomas Konstandin🇩🇪 · Geraldine Servant🇩🇪

   Can the cosmological dynamics responsible for settling down the present values of the Cabibbo-Kobayashi-Maskawa matrix be related to electroweak symmetry breaking? If the Standard Model Yukawa couplings varied in the early universe and started with order one values before electroweak symmetry breaking, the CP violation associated with the CKM matrix could be the origin of the matter-antimatter asymmetry. The large effective Yukawa couplings which lead to the enhanced CP violation can also help in achieving a strong first-order electroweak phase transition. We study in detail the feasibility of this idea by implementing dynamical Yukawa couplings in the context of the Froggatt--Nielsen mechanism. We discuss two main realizations of such a mechanism, related phenomenology, cosmological and collider bounds, and provide an estimate of the baryonic yield. A generic prediction is that this scenario always features a new scalar field below the electroweak scale. We point out ways to get around this conclusion.

   hep-phJHEP(2016)·51 citations
2. 02*

   CP violation in multibody decays of beauty baryons

   Gauthier Durieux🇩🇪

   Beauty baryons are being observed in large numbers in the LHCb detector. The rich kinematic distributions of their multibody decays are therefore becoming accessible and provide us with new opportunities to search for CP violation. We analyse the angular distributions of some three- and four-body decays of spin-$1/2$ baryons using the Jacob-Wick helicity formalism. The asymmetries that provide access to small differences of CP-odd phases between decay amplitudes of identical CP-even phases are notably discussed. The understanding gained on processes featuring specific resonant intermediate states allows us to establish which asymmetries are relevant for what purpose. It is for instance shown that some CP-odd angular asymmetries measured by the LHCb collaboration in the ${\Lambda }_b\to \Lambda \phi \to p\pi K^{+}{K}^{-}$ decay are expected to vanish identically.

   hep-phhep-exJHEP(2016)·17 citations
3. 03*

   Study of weak corrections to Drell-Yan, top-quark pair and dijet Production at high energies with MCFM

   John M. Campbell🇺🇸 · Doreen Wackeroth🇺🇸 · Jia Zhou🇺🇸

   Electroweak (EW) corrections can be enhanced at high energies due to the soft or collinear radiation of virtual and real $W$ and $Z$ bosons that result in Sudakov-like corrections of the form ${\alpha }_W^l{\log }^n(Q^2/M_{W,Z}^2)$, where ${\alpha }_W=\alpha /(4\pi {\sin }^2{\theta }_W)$ and $n\le 2l-1$. The inclusion of EW corrections in predictions for hadron colliders is therefore especially important when searching for signals of possible new physics in distributions probing the kinematic regime $Q^2\gg M_V^2$. Next-to-leading order (NLO) EW corrections should also be taken into account when their size ($\mathcal{O}(\alpha )$) is comparable to that of QCD corrections at next-to-next-to-leading order (NNLO) ($\mathcal{O}({\alpha }_s^2)$). To this end we have implemented the NLO weak corrections to the Neutral-Current Drell-Yan process, top-quark pair production and di-jet production in the parton-level Monte-Carlo program MCFM. This enables a combined study with the corresponding QCD corrections at NLO and NNLO. We provide both the full NLO weak corrections and their Sudakov approximation since the latter is often used for a fast evaluation of weak effects at high energies and can be extended to higher orders. With both the exact and approximate results at hand, the validity of the Sudakov approximation can be readily quantified

   hep-phPRD(2016)·45 citations
4. 04*

   Magnetic Moments of Octet Baryons in Hot and Dense Nuclear Matter

   Harpreet Singh🇮🇳 · Arvind Kumar🇮🇳 · Harleen Dahiya🇮🇳

   We have calculated the in-medium magnetic moments of octet baryons in the presence of hot and dense symmetric nuclear matter. Effective magnetic moments of baryons have been derived from medium modified quark masses within chiral SU(3) quark mean field model. Further, for better insight of medium modification of baryonic magnetic moments, we have considered the explicit contributions from the valence quarks, sea quarks as well as sea orbital angular momentum of sea quarks. These effects have been successful in giving the description of baryonic magnetic moments in vacuum. The magnetic moments of baryons are found to vary significantly as a function of density of nuclear medium.

   hep-phnucl-thCPC(2017)·22 citations
5. 05*

   Phenomenology of additional scalar bosons at the LHC

   Mukesh Kumar🇿🇦 · Stefan von Buddenbrock🇿🇦 · Nabarun Chakrabarty🇮🇳 · Alan S. Cornell🇿🇦 · Deepak Kar🇿🇦 · Tanumoy Mandal🇸🇪 · Bruce Mellado🇿🇦 · Biswarup Mukhopadhyaya🇮🇳 · Robert G. Reed🇿🇦 · Xifeng Ruan🇿🇦

   The confirmation of the Higgs boson in Run I data at the Large Hadron Collider (LHC) and the excesses in recent Run II data suggest scenarios beyond the Standard Model (SM). We pursue a study in a minimal model which is an extension of a scalar doublet in the SM known as two-Higgs doublet model (THDM). Following earlier suggestions two real scalars $\chi$ and $S$ have been introduced in the THDM where $\chi$ is treated as a candidate for dark matter. $\chi$ does not receive any vacuum expectation value ($vev$) in the model whereas the Higgs-like scalar $S$ acquires $vev$. This allows small mixing between the $CP$-even scalars of the THDM, $h$, $H$ and $S$. In this study the mass spectrum of new scalars is taken to be $2m_h<m_H<2m_t$, $m_{\chi }<m_h/2$, $m_h\lesssim m_S\lesssim m_H-m_h$, $m_A>2m_t$ and $m_H^{\pm }<m_A$, where $m_h$ and $m_t$ is masses of the SM Higgs and top-quark respectively, $m_H,m_A$ and $m_{H^{\pm }}$ are the masses of the heavy $CP$-even scalar $H$, $CP$-odd scalar $A$, and charged Higgs $H^{\pm }$, respectively. A partial list of potential search channels at the LHC has been provided with possible phenomenological consequences. The expected phenomenology and constraints on parameters are also discussed in a model-independent approach .

   hep-ph2 citations
6. 06*

   Gravitino production in a thermal Universe revisited

   Richa Arya🇮🇳 · Namit Mahajan🇮🇳 · Raghavan Rangarajan🇮🇳

   We study the production of spin 1/2 gravitinos in a thermal Universe. Taking into account supersymmetry breaking due to the finite thermal energy density of the Universe, there is a large enhancement in the cross section of production of these gravitino states. We consider gravitinos with zero temperature masses of 0.1 eV, 1 keV, 100 GeV and 30 TeV as representative of gauge mediated, gravity mediated and anomaly mediated supersymmetry breaking scenarios. We find that the abundance of gravitinos produced in the early Universe is very high for gravitinos of mass 1 keV and 100 GeV. The gravitino abundances can be sufficiently suppressed if the reheat temperature is less than 100 GeV and $4\cdot 10^4$ gev respectively. However such low reheat temperatures will rule out many models of baryogenesis including those via leptogenesis.

   ↳ astro-ph.COhep-phPLB(2017)·6 citations
7. 07*

   Dynamical freeze-out criterion in a hydrodynamical description of Au + Au collisions at $\sqrt{s_{\mathrm{NN}}}=200$ GeV and Pb + Pb collisions at $\sqrt{s_{\mathrm{NN}}}=2760$ GeV

   Saeed Ahmad🇮🇳 · Hannu Holopainen🇩🇪 · Pasi Huovinen🇩🇪

   In hydrodynamical modeling of ultrarelativistic heavy-ion collisions, the freeze-out is typically assumed to take place at a surface of constant temperature or energy density. A more physical approach is to assume that freeze-out takes place at a surface of constant Knudsen number. We evaluate the Knudsen number as a ratio of the expansion rate of the system to the pion scattering rate, and apply the constant Knudsen number freeze-out criterion to ideal hydrodynamical description of heavy-ion collisions at RHIC ($\sqrt{s_{\mathrm{NN}}}=200$ GeV) and the LHC ($\sqrt{s_{\mathrm{NN}}}=2760$ GeV) energies. We see that once the numerical values of freeze-out temperature and freeze-out Knudsen number are chosen to produce similar $p_T$ distributions, the elliptic and triangular anisotropies are similar too, in both event-by-event and averaged initial state calculations.

   ↳ nucl-thhep-phnucl-exPRC(2017)·15 citations
8. 08*

   Toward establishing low-lying $\Lambda$ and $\Sigma$ hyperon resonances with the $\bar{K}+d\to \pi +Y+N$ reaction

   H. Kamano🇯🇵 · T.-S. H. Lee🇺🇸

   A model for the $\bar{K}d\to \pi YN$ reactions with $Y=\Lambda ,\Sigma$ is developed, aiming at establishing the low-lying $\Lambda$ and $\Sigma$ hyperon resonances through analyzing the forthcoming data from the J-PARC E31 experiment. The off-shell amplitudes generated from the dynamical coupled-channels (DCC) model, which was developed in Kamano et al. [Phys. Rev. C 90, 065204 (2014)], are used as input to the calculations of the elementary $\bar{K}N\to \bar{K}N$ and $\bar{K}N\to \pi Y$ subprocesses in the $\bar{K}d\to \pi YN$ reactions. It is shown that the cross sections for the J-PARC E31 experiment with a rather high incoming-$\bar{K}$ momentum, $|{\vec{p}}_{\bar{K}}|=1$ GeV, can be predicted reliably only when the input $\bar{K}N\to \bar{K}N$ amplitudes are generated from a $\bar{K}N$ model, such as the DCC model used in this investigation, which describes the data of the $\bar{K}N$ reactions at energies far beyond the $\bar{K}N$ threshold. We find that the data of the threefold differential cross section $d\sigma /(d{M}_{\pi \Sigma }d{\Omega }_{p_n})$ for the $K^{-}d\to \pi \Sigma n$ reaction below the $\bar{K}N$ threshold can be used to test the predictions of the resonance poles associated with $\Lambda (1405)$. We also find that the momentum dependence of the threefold differential cross sections for the $K^{-}d\to {\pi }^{-}\Lambda p$ reaction can be used to examine the existence of a low-lying $J^P=1/2^{+}$ $\Sigma$ resonance with a pole mass $M_R=1457-i39$ MeV, which was found from analyzing the $K^{-}p$ reaction data within the employed DCC model.

   ↳ nucl-thhep-exhep-phnucl-exPRC(2016)·19 citations
9. 09*

   Anomalous transport in second order hydrodynamics

   Eugenio Megias🇩🇪 · Manuel Valle🇪🇸

   We study the non-dissipative transport effects appearing at second order in the hydrodynamic expansion for a non-interacting gas of chiral fermions by using the partition function formalism. We discuss some features of the corresponding constitutive relations, derive the explicit expressions for the conductivities and compare with existing results in the literature.

   ↳ hep-thhep-phEPJ Web Conf.(2016)·1 citation
10. 10*

    Implementing quantum electrodynamics with ultracold atomic systems

    V. Kasper🇩🇪 · F. Hebenstreit🇨🇭 · F. Jendrzejewski🇩🇪 · M. K. Oberthaler🇩🇪 · J. Berges🇩🇪

    We discuss the experimental engineering of model systems for the description of QED in one spatial dimension via a mixture of bosonic ${}^{23}$Na and fermionic ${}^6$Li atoms. The local gauge symmetry is realized in an optical superlattice, using heteronuclear boson-fermion spin-changing interactions which preserve the total spin in every local collision. We consider a large number of bosons residing in the coherent state of a Bose-Einstein condensate on each link between the fermion lattice sites, such that the behavior of lattice QED in the continuum limit can be recovered. The discussion about the range of possible experimental parameters builds, in particular, upon experiences with related setups of fermions interacting with coherent samples of bosonic atoms. We determine the atomic system's parameters required for the description of fundamental QED processes, such as Schwinger pair production and string breaking. This is achieved by benchmark calculations of the atomic system and of QED itself using functional integral techniques. Our results demonstrate that the dynamics of one-dimensional QED may be realized with ultracold atoms using state-of-the-art experimental resources. The experimental setup proposed may provide a unique access to longstanding open questions for which classical computational methods are no longer applicable.

    ↳ cond-mat.quant-gashep-phNew J.Phys.(2017)·130 citations
11. 11*

    Stabilizing semilocal strings by polarization

    Minoru Eto🇯🇵 · Muneto Nitta🇯🇵 · Kohei Sakurai🇯🇵

    Semilocal strings are vortices in the extended Abelian-Higgs model with two complex Higgs scalar fields among which a global $SU(2)$ symmetry acts. They are known to be stable (unstable against expansion) in type-I (II) superconductors, in which gauge field is heavier (lighter) than the Higgs scalar field. In this paper, we find that vortices can be stabilized in the whole parameter region including the type-II region by adding a potential term breaking the $SU(2)$ symmetry. We construct numerical solutions in various parameters and determine the vortex phase diagram consisting of six phases. In two phases, a vortex is polarized, that is, split into two half-quantized vortices with a certain distance, to form a vortex molecule, while in the rests a vortex is identical to the conventional Abrikosov-Nielsen-Olesen vortex.

    ↳ hep-thhep-phJHEP(2016)·7 citations
12. 12*

    Measurement of the low-energy quenching factor in germanium using an ${}^{88}$Y/Be photoneutron source

    B.J. Scholz🇺🇸 · A.E. Chavarria🇺🇸 · J.I. Collar🇺🇸 · P. Privitera🇺🇸 · A.E. Robinson🇺🇸

    We employ an ${}^{88}$Y/Be photoneutron source to derive the quenching factor for neutron-induced nuclear recoils in germanium, probing recoil energies from a few hundred eV${}_{nr}$ to 8.5keV${}_{nr}$. A comprehensive Monte Carlo simulation of our setup is compared to experimental data employing a Lindhard model with a free electronic energy loss $k$ and an adiabatic correction for sub-keV${}_{nr}$ nuclear recoils. The best fit $k=0.179\pm 0.001$ obtained using a Monte Carlo Markov Chain (MCMC) ensemble sampler is in good agreement with previous measurements, confirming the adequacy of the Lindhard model to describe the stopping of few-keV ions in germanium crystals at a temperature of $\sim$77 K. This value of $k$ corresponds to a quenching factor of 13.7 % to 25.3 % for nuclear recoil energies between 0.3 keV${}_{nr}$ and 8.5 keV${}_{nr}$, respectively.

    ↳ physics.ins-detastro-ph.COastro-ph.IMhep-ex+2PRD(2016)·70 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.