Wed·Feb 15, 2017Wednesday·February 15, 2017

1. 01*

   How light a higgsino or a wino dark matter can become in a compressed scenario of MSSM

   Manimala Chakraborti🇩🇪 · Utpal Chattopadhyay🇮🇳 · Sujoy Poddar🇮🇳

   Higgsinos and Wino have strong motivations for being Dark Matter (DM) candidates in supersymmetry, but their annihilation cross sections are quite large. For thermal generation and a single component DM setup the higgsinos or wino may have masses of around 1 or 2-3 TeV respectively. For such DM candidates, a small amount of slepton coannihilation may decrease the effective DM annihilation cross section. This, in turn reduces the lower limit of the relic density satisfied DM mass by more than 50%. Almost a similar degree of reduction of the same limit is also seen for squark coannihilations. However, on the contrary, for near degeneracy of squarks and higgsino DM, near its generic upper limit, the associated coannihilations may decrease the relic density, thus extending the upper limit towards higher DM masses. We also compute the direct and indirect detection signals. Here, because of the quasi-mass degeneracy of the squarks and the LSP, we come across a situation where squark exchange diagrams may contribute significantly or more strongly than the Higgs exchange contributions in the spin-independent direct detection cross section of DM. For the higgsino-DM scenario, we observe that a DM mass of 600 GeV to be consistent with WMAP/PLANCK and LUX data for sfermion coannihilations. The LUX data itself excludes the region of 450 to 600 GeV, by a half order of magnitude of the cross-section, well below the associated uncertainty. The similar combined lower limit for a wino DM is about 1.1 TeV. There is hardly any collider bound from the LHC for squarks and sleptons in such a compressed scenario where sfermion masses are close to the mass of a higgsino/wino LSP.

   hep-phJHEP(2017)·48 citations
2. 02*

   What are the low-$Q$ and large-$x$ boundaries of collinear QCD factorization theorems?

   E. Moffat🇺🇸 · W. Melnitchouk🇺🇸 · T. C. Rogers🇺🇸 · N. Sato🇺🇸

   Familiar factorized descriptions of classic QCD processes such as deeply-inelastic scattering (DIS) apply in the limit of very large hard scales, much larger than nonperturbative mass scales and other nonperturbative physical properties like intrinsic transverse momentum. Since many interesting DIS studies occur at kinematic regions where the hard scale, $Q\sim$ 1-2 GeV, is not very much greater than the hadron masses involved, and the Bjorken scaling variable $x_{bj}$ is large, $x_{bj}\gtrsim 0.5$, it is important to examine the boundaries of the most basic factorization assumptions and assess whether improved starting points are needed. Using an idealized field-theoretic model that contains most of the essential elements that a factorization derivation must confront, we retrace the steps of factorization approximations and compare with calculations that keep all kinematics exact. We examine the relative importance of such quantities as the target mass, light quark masses, and intrinsic parton transverse momentum, and argue that a careful accounting of parton virtuality is essential for treating power corrections to collinear factorization. We use our observations to motivate searches for new or enhanced factorization theorems specifically designed to deal with moderately low-$Q$ and large-$x_{bj}$ physics.

   hep-phhep-exnucl-thPRD(2017)·21 citations
3. 03*

   Scalar Production in Association with a Z Boson at LHC and ILC: the Mixed Higgs-Radion Case of Warped Models

   Andrei Angelescu🇫🇷 · Grégory Moreau🇫🇷 · François Richard🇫🇷

   The radion scalar field might be the lightest new particle predicted by extra-dimensional extensions of the Standard Model. It could thus lead to the first signatures of new physics at the LHC collider. We perform a complete study of the radion production in association with the Z gauge boson in the custodially protected warped model with a brane-localised Higgs boson addressing the gauge hierarchy problem. Radion-Higgs mixing effects are present. Such a radion production receives possibly resonant contributions from the Kaluza-Klein excitations of the Z boson as well as the extra neutral gauge boson (Z'). All the exchange and mixing effects induced by those heavy bosons are taken into account in the radion coupling and rate calculations. The investigation of the considered radion production at LHC allows to be sensitive to some parts of the parameter space but only the ILC program at high luminosity would cover most of the theoretically allowed parameter space via the studied reaction. Complementary tests of the same theoretical parameters can be realised through the high accuracy measurements of the Higgs couplings at ILC. The generic sensitivity limits on the rates discussed for the LHC and ILC potential reach can be applied to the searches for other (light) exotic scalar bosons.

   hep-phhep-exPRD(2017)·20 citations
4. 04*

   Gauge Singlet Vector-like Fermion Dark Matter, LHC Diphoton Rate and Direct Detection

   Shrihari Gopalakrishna🇮🇳 · Tuhin Subhra Mukherjee🇮🇳

   We study a gauge-singlet vector-like fermion hidden-sector dark matter model, in which the communication between the dark matter and the visible standard model sector is via the Higgs-portal scalar-Higgs mixing, and also via a hidden-sector scalar with loop-level couplings to two gluons and also to two hypercharge gauge bosons induced by a vector-like quark. We find that the Higgs-portal possibility is stringently constrained to be small by the recent LHC di-Higgs search limits, and the loop-induced couplings are important to include. In the model parameter space, we present the dark matter relic-density, the dark-matter-nucleon direct-detection scattering cross-section, the LHC diphoton rate from gluon-gluon fusion, and the theoretical upper-bounds on the fermion-scalar couplings from perturbative unitarity.

   hep-phAdv.High Energy Phys.(2017)·7 citations
5. 05*

   Electroweak monopoles and the electroweak phase transition

   Suntharan Arunasalam🇦🇺 · Archil Kobakhidze🇦🇺

   We consider an isolated electroweak monopole solution within the Standard Model with a non-linear Born-Infeld extension of the hypercharge gauge field. Monopole (and dyon) solutions in such an extension are regular and their masses are predicted to be proportional to the Born-Infeld mass parameter. We argue that cosmological production of electroweak monopoles may delay the electroweak phase transition and make it more strongly first order for monopole masses $M\gtrsim 9.3\cdot 10^3$ TeV, while the nucleosynthesis constraints on the abundance of relic monopoles impose the bound $M\lesssim 2.3\cdot 10^4$ TeV. The monopoles with a mass in this shallow range may be responsible for the dynamical generation of the matter-antimatter asymmetry during the electroweak phase transition.

   hep-phastro-ph.HEhep-thEPJC(2017)·51 citations
6. 06*

   Newly observed ${\Lambda }_c(2860{)}^{+}$ at LHCb and its \emph{D}-wave partners ${\Lambda }_c(2880{)}^{+}$, ${\Xi }_c(3055{)}^{+}$ and ${\Xi }_c(3080{)}^{+}$

   Bing Chen🇨🇳 · Xiang Liu🇨🇳 · Ailin Zhang🇨🇳

   New resonance ${\Lambda }_c(2860{)}^{+}$, reported by LHCb, is a key to establish \emph{D}-wave charmed and charmed-strange baryon families. In this work, we first carry out an analysis of mass spectra of the $\lambda$-mode excited charmed and charmed-strange baryon states, which may reveal the relation of ${\Lambda }_c(2860{)}^{+}$, ${\Lambda }_c(2880{)}^{+}$, ${\Xi }_c(3055{)}^{+}$ and ${\Xi }_c(3080{)}^{+}$, $i.e.$, ${\Lambda }_c(2860{)}^{+}$ and ${\Lambda }_c(2880{)}^{+}$ can form a \emph{D}-wave doublet $[3/2^{+},5/2^{+}]$ while ${\Xi }_c(3055{)}^{+}$ and ${\Xi }_c(3080{)}^{+}$ are the strange partners of ${\Lambda }_c(2860{)}^{+}$ and ${\Lambda }_c(2880{)}^{+}$, respectively. Further study of their two-body Okubo-Zweig-Iizuka-allowed decays supports ${\Lambda }_c(2860{)}^{+}$ and ${\Xi }_c(3055{)}^{+}$ as the \emph{D}-wave charmed and charmed-strange baryons, respectively, with $J^P=3/2^{+}$. For ${\Lambda }_c(2880{)}^{+}$ and ${\Xi }_c(3080{)}^{+}$, however, there exist some difficulties under the \emph{D}-wave assignment with $J^P=5/2^{+}$ since the experimental widths and some ratios of partial width of ${\Lambda }_c(2880{)}^{+}$ and ${\Xi }_c(3080{)}^{+}$ cannot be reproduced in our calculation.

   hep-phhep-exPRD(2017)·42 citations
7. 07*

   Using the Tsallis distribution for hadron spectra in $pp$ collisions: Pions and quarkonia at $\sqrt{s}$ = 5--13000 GeV

   Smbat Grigoryan🇷🇺

   A thermal model, based on the Tsallis distribution and blast-wave model, is proposed to compute hadron double-differential spectra $d^{2}N/d{p}_{T}dy$ in $pp$ (also high energy $p\overline{p}$) collisions. It successfully describes the available experimental data on pion and quarkonia ($\varphi$, $J/\psi$, $\psi (2S)$, ${\rm Y}$ family) production at energies from $\sqrt{s}=5$ GeV to the LHC ones. Simple parametrizations for the $\sqrt{s}$ dependence of the model parameters are provided allowing predictions for the yields of these particles at new collision energies. The model can be used also for the pion Bose-Einstein correlation studies.

   hep-phPRD(2017)·47 citations
8. 08*

   Precise Determination of the U-235 Reactor Antineutrino Cross Section per Fission

   Carlo Giunti🇮🇹

   We consider the possibility that the reactor antineutrino anomaly is due to a miscalculation of one or more of the ${}^{235}\text{U}$, ${}^{238}\text{U}$, ${}^{239}\text{Pu}$, and ${}^{241}\text{Pu}$ reactor antineutrino fluxes. From the fit of the data we obtain the precise determination ${\sigma }_{f,235}=(6.33\pm 0.08)\times 10^{-43}{\text{cm}}^2/\text{fission}$ of the ${}^{235}\text{U}$ cross section per fission, which is more precise than the calculated value and differs from it by $2.2\sigma$. The cross sections per fission of the other fluxes have large uncertainties and in practice their values are undetermined by the fit. We conclude that it is very likely that at least the calculation of the ${}^{235}\text{U}$ flux must be revised.

   hep-phhep-exnucl-exJ.Phys.Conf.Ser.(2019)·0 citations
9. 09*

   Critical end point in a thermo-magnetic nonlocal NJL model

   F. Marquez🇨🇱 · R. Zamora🇨🇱

   In this article we explore the critical end point in the $T-\mu$ phase diagram of a thermomagnetic nonlocal Nambu--Jona-Lasinio model in the weak field limit. We work with the Gaussian regulator, and find that a crossover takes place at $\mu ,B=0$. The crossover turns to a first order phase transition as the chemical potential or the magnetic field increase. The critical end point of the phase diagram occurs at a higher temperature and lower chemical potential as the magnetic field increases. This result is in accordance to similar findings in other effective models. We also find there is a critical magnetic field, for which a first order phase transition takes place even at $\mu =0$.

   hep-phInt.J.Mod.Phys.A(2017)·7 citations
10. 10*

    Just a Scalar in THDM

    Busra Nis🇹🇷 · Ali Cici🇹🇷 · Zerrin Kirca🇹🇷 · Cem Salih Un🇹🇷

    We review the THDM model in which one of the Higgs doublets does not develop a vacuum expectation value. In this case, the Higgs fields with zero VEV does not contribute to the physical masses of the SM particles, and hence, its interactions with the SM particles can have more freedom than in the case of usual considerations on the THDM models. We show that the stability of the Higgs potential minima can be maintained. All the Higgs boson masses are found lighter than about 300 GeV in the low scale spectrum when v_1=0. Such light mass scales are in the detectable regime, and hence, the SM predictions and the experimental results are essential to be applied in the analyses. Especially the decay channels; h-->W^+ W^- and h-->bb exclude most of the solutions, while it is still possible to realize a small region, which coincides with the SM predictions. We highlight that it is also possible to realize an excess in h--> gamma gamma decay channel, even one applies the constraints from the Higgs boson decays into W^+ W^- and bb. In addition, if one assumes H is the SM-like Higgs boson of mass about 125 GeV, the solutions with m_h <~ 125 GeV can be acceptable. In this case, the solutions can still be realized consistent with the SM predictions; however, an excess in H --> gamma gamma cannot be observed, while the implications for this channel in THDM can stay in the SM prediction rates at most. Even though the light masses of the Higgs bosons can be favored in resolution to discrepancy between the Standard Model and the experiment in the muon anomalous magnetic moment measurements, we find that it is not possible to accommodate such a resolution with BR(b --> s gamma) results simultaneously.

    hep-ph1 citation
11. 11*

    Constraining secret gauge interactions of neutrinos by meson decays

    Pouya Bakhti🇮🇷 · Yasaman Farzan🇮🇷

    Secret coupling of neutrinos to a new light vector boson, $Z^{\prime }$, with a mass smaller than 100 MeV is motivated within a myriad of scenarios which are designed to explain various anomalies in particle physics and cosmology. Due to the longitudinal component of the massive vector boson, the rates of three-body decay of charged mesons ($M$) such as the pion and the kaon to the light lepton plus neutrino and $Z^{\prime }$ ($M\to l\nu Z^{\prime }$) are enhanced by a factor of $(m_M/m_{Z^{\prime }}{)}^2$. On the other hand, the standard two body decay $M\to l\nu$ is suppressed by a factor of $(m_l/m_M{)}^2$ due to chirality. We show that in the case of ($M\to e\nu Z^{\prime }$), the enhancement of $m_M^4/m_e^2{m}_{Z^{\prime }}^2\sim 10^8-10^{10}$ relative to two-body decay ($M\to e\nu$) enables us to probe very small values of gauge coupling for ${\nu }_e$. The strongest bound comes from the $R_K\equiv Br(K\to e+\nu )/Br(K\to \mu +\nu )$ measurement in the NA62 experiment. The bound can be significantly improved by customized searches for signals of three-body charged meson decay into the positron plus missing energy in the NA62 and/or PIENU data.

    hep-phhep-exPRD(2017)·47 citations
12. 12*

    Quarkonium production at the LHC: a phenomenological analysis of surprisingly simple data patterns

    Pietro Faccioli · Mariana Araújo · Valentin Knünz · Ilse Krätschmer · Carlos Lourenço · João Seixas

    The LHC quarkonium production measurements reveal a startling observation: the J/$\psi$, $\psi$(2S), ${\chi }_{c1,2}$ and ${\rm Y}$(nS) $p_{\mathrm{T}}$-differential cross sections are compatible with one universal momentum scaling pattern. Considering also the absence of strong polarizations of directly and indirectly produced S-wave mesons, we are led to the conclusion that there is currently no evidence of a dependence of the partonic production mechanisms on the quantum numbers and mass of the final state. The experimental observations supporting this universal production scenario are remarkably significant, as shown by a new analysis approach, unbiased by specific theoretical calculations of partonic cross sections, which are only considered a posteriori, in comparisons with the data-driven results.

    hep-ph
13. 13*

    Quarkonium production at the LHC: a data-driven analysis of NRQCD's predictions

    Pietro Faccioli🇵🇹 · Mariana Araújo🇨🇭 · Valentin Knünz🇨🇭 · Ilse Krätschmer🇦🇹 · Carlos Lourenço🇨🇭 · João Seixas🇵🇹

    While non-relativistic QCD (NRQCD) foresees a variety of elementary quarkonium production mechanisms naturally leading to state-dependent kinematic patterns, the LHC cross sections and polarization measurements reveal a remarkably simple production scenario, independent of the quantum numbers and masses of the quarkonia. Surprisingly, NRQCD is able to accommodate the observed universal scenario, through a series of conspiring cancellations smoothing out its otherwise variegated hierarchy of mechanisms. This seemingly unnatural solution implies that the ${\chi }_{c1}$ and ${\chi }_{c2}$ polarizations, not yet measured, are strong and opposite, representing the only potential exception to a remarkably simple picture of quarkonium production. The observation of a large difference between ${\chi }_{c2}$ and ${\chi }_{c1}$ polarizations, which cannot be indirectly extracted from existing measurements because they mutually cancel each other in their contribution to the observed J/$\psi$ production, would be a smoking gun signal finally proving the multifaceted but mysteriously elusive structure of NRQCD. On the other hand, the measurement of two similar, small polarizations will urge improved P-wave calculations, if not a substantial revision of the NRQCD hierarchies.

    hep-phPLB(2017)·24 citations
14. 14*

    Simplifying differential equations for multi-scale Feynman integrals beyond multiple polylogarithms

    Luise Adams🇩🇪 · Ekta Chaubey🇩🇪 · Stefan Weinzierl🇩🇪

    In this paper we exploit factorisation properties of Picard-Fuchs operators to decouple differential equations for multi-scale Feynman integrals. The algorithm reduces the differential equations to blocks of the size of the order of the irreducible factors of the Picard-Fuchs operator. As a side product, our method can be used to easily convert the differential equations for Feynman integrals which evaluate to multiple polylogarithms to $\epsilon$-form.

    hep-phhep-thPRL(2017)·102 citations
15. 15*

    Anomalies in (semi)-leptonic $B$ decays $B^{\pm }\to {\tau }^{\pm }\nu$, $B^{\pm }\to D{\tau }^{\pm }\nu$ and $B^{\pm }\to D^{\ast }{\tau }^{\pm }\nu$, and possible resolution with sterile neutrino

    G. Cvetič🇨🇱 · Francis Halzen🇺🇸 · C. S. Kim🇰🇷 · Sechul Oh🇰🇷

    The universality of the weak interactions can be tested in semileptonic $b\to c$ transitions, and in particular in the ratios $R(D^{(\ast )})\equiv \Gamma (B\to D^{(\ast )}\tau \nu )/\Gamma (B\to D^{(\ast )}\ell \nu )$ (where $\ell =\mu$ or $e$). Due to the recent differences between the experimental measurements of these observables by BaBar, Belle and LHCb on the one hand and the Standard Model predicted values on the other hand, we study the predicted ratios $R(D^{(\ast )})=\Gamma (B\to D^{(\ast )}\tau +$ "missing" $)/\Gamma (B\to D^{(\ast )}\ell \nu )$ in scenarios with an additional sterile heavy neutrino of mass $\sim 1$ GeV. Further, we evaluate the newly defined ratio $R(0)\equiv \Gamma (B\to \tau +$ "missing" $)/\Gamma (B\to \mu \nu )$ in such scenarios, in view of the future possibilities of measuring the quantity at Belle-II.

    hep-phCPC(2017)·45 citations
16. 16*

    Cosmological CP odd axion field as the coherent Berry's phase of the Universe

    Shuailiang Ge🇨🇦 · Xunyu Liang🇨🇦 · Ariel Zhitnitsky🇨🇦

    We consider a dark matter (DM) model offering a very natural explanation of the observed relation, ${\Omega }_{\mathrm{dark}}\sim {\Omega }_{\mathrm{visible}}$. This generic consequence of the model is a result of the common origin of both types of matter (DM and visible) which are formed during the same QCD transition. The masses of both types of matter in this framework are proportional to one and the same dimensional parameter of the system, ${\Lambda }_{\mathrm{QCD}}$. The focus of the present work is the detail study of the dynamics of the $\mathcal{C}\mathcal{P}$-odd coherent axion field $a(x)$ just before the QCD transition. We argue that the baryon charge separation effect on the largest possible scales inevitably occurs as a result of merely existence of the coherent axion field in early Universe. It leads to preferential formation of one species of nuggets on the scales of the visible Universe where the axion field $a(x)$ is coherent. A natural outcome of this preferential evolution is that only one type of the visible baryons remains in the system after the nuggets complete their formation. This represents a specific mechanism on how the baryon charge separation mechanism (when the Universe is neutral, but visible part of matter consists the baryons only) replaces the conventional "baryogenesis" scenarios.

    hep-phastro-ph.COastro-ph.HEnucl-thPRD(2017)·38 citations
17. 17*

    Fock-space projection operators for semi-inclusive final states

    Robert Dickinson🇬🇧 · Jeff Forshaw🇬🇧 · Peter Millington🇬🇧

    We present explicit expressions for Fock-space projection operators that correspond to realistic final states in scattering experiments. Our operators automatically sum over unobserved quanta and account for non-emission into sub-regions of momentum space.

    ↳ hep-thhep-phquant-phPLB(2017)·5 citations
18. 18*

    The Power of Perturbation Theory

    Marco Serone🇮🇹 · Gabriele Spada🇮🇹 · Giovanni Villadoro🇮🇹

    We study quantum mechanical systems with a discrete spectrum. We show that the asymptotic series associated to certain paths of steepest-descent (Lefschetz thimbles) are Borel resummable to the full result. Using a geometrical approach based on the Picard-Lefschetz theory we characterize the conditions under which perturbative expansions lead to exact results. Even when such conditions are not met, we explain how to define a different perturbative expansion that reproduces the full answer without the need of transseries, i.e. non-perturbative effects, such as real (or complex) instantons. Applications to several quantum mechanical systems are presented.

    ↳ hep-thcond-mat.stat-mechhep-phmath-ph+2JHEP(2017)·66 citations
19. 19*

    Weighing neutrinos in the scenario of vacuum energy interacting with cold dark matter: application of the parameterized post-Friedmann approach

    Rui-Yun Guo🇨🇳 · Yun-He Li🇨🇳 · Jing-Fei Zhang🇨🇳 · Xin Zhang🇨🇳

    We constrain the neutrino mass in the scenario of vacuum energy interacting with cold dark matter by using current cosmological observations. To avoid the large-scale instability problem in interacting dark energy models, we employ the parameterized post-Friedmann (PPF) approach to do the calculation of perturbation evolution, for the $Q=\beta H{\rho }_{\mathrm{c}}$ and $Q=\beta H{\rho }_{\Lambda }$ models. The current observational data sets used in this work include Planck (cosmic microwave background), BSH (baryon acoustic oscillations, type Ia supernovae, and Hubble constant), and LSS (redshift space distortions and weak lensing). According to the constraint results, we find that $\beta >0$ at more than $1\sigma$ level for the $Q=\beta H{\rho }_{\mathrm{c}}$ model, which indicates that cold dark matter decays into vacuum energy; while $\beta =0$ is consistent with the current data at $1\sigma$ level for the $Q=\beta H{\rho }_{\Lambda }$ model. Taking the $\Lambda$CDM model as a baseline model, we find that a smaller upper limit, $\sum m_{\nu }<0.11$ eV ($2\sigma$), is induced by the latest BAO BOSS DR12 data and the Hubble constant measurement $H_0=73.00\pm 1.75$ km~s${}^{-1}$~Mpc${}^{-1}$. For the $Q=\beta H{\rho }_{\mathrm{c}}$ model, we obtain $\sum m_{\nu }<0.20$ eV ($2\sigma$) from Planck+BSH. For the $Q=\beta H{\rho }_{\Lambda }$ model, $\sum m_{\nu }<0.10$ eV ($2\sigma$) and $\sum m_{\nu }<0.14$ eV ($2\sigma$) are derived from Planck+BSH and Planck+BSH+LSS, respectively. We show that these smaller upper limits on $\sum m_{\nu }$ are affected more or less by the tension between $H_0$ and other observational data.

    ↳ astro-ph.COgr-qchep-phhep-thJCAP(2017)·79 citations
20. 20*

    Transport coefficients of two-flavor quark matter from the Kubo formalism

    Arus Harutyunyan🇩🇪 · Dirk H. Rischke🇩🇪 · Armen Sedrakian🇩🇪

    The transport coefficients of quark matter at non-zero chemical potential and temperature are computed within the two-flavor Nambu--Jona-Lasinio model. We apply the Kubo formalism to obtain the thermal ($\kappa$) and electrical ($\sigma$) conductivities as well as an update of the shear viscosity ($\eta$) by evaluating the corresponding equilibrium two-point correlation functions to leading order in the $1/N_c$ expansion. The Dirac structure of the self-energies and spectral functions is taken into account as these are evaluated from the meson-exchange Fock diagrams for on-mass-shell quarks. We find that the thermal and electrical conductivities are decreasing functions of temperature and density above the Mott temperature $T_{\mathrm{M}}$ of dissolution of mesons into quarks, the main contributions being generated by the temporal and vector components of the spectral functions. The coefficients show a universal dependence on the ratio $T/T_{\mathrm{M}}$ for different densities, i.e., the results differ by a chemical-potential dependent constant. We also show that the Wiedemann-Franz law for the ratio $\sigma /\kappa$ does not hold. The ratio $\eta /s$, where $s$ is the entropy density, is of order of unity (or larger) close to the Mott temperature and, as the temperature increases, approaches the AdS/CFT bound $1/4\pi$. It is also conjectured that the ratio $\kappa T/c_V$, with $c_V$ being the specific heat, is bounded from below by $1/18$.

    ↳ nucl-thastro-ph.HEhep-phPRD(2017)·33 citations
21. 21*

    Hypermagnetic knots and gravitational radiation at intermediate frequencies

    Massimo Giovannini🇨🇭

    The maximally gyrotropic configurations of the hypermagnetic field at the electroweak epoch can induce a stochastic background of relic gravitational waves with comoving frequencies ranging from the $\mu$Hz to the kHz. Using two complementary approaches we construct a physical template family for the emission of the gravitational radiation produced by the hypermagnetic knots. The current constraints and the presumed sensitivities of the advanced wide-band interferometers (both terrestrial and space-borne) are combined to infer that the lack of observations at intermediate frequencies may invalidate the premise of baryogenesis models based (directly or indirectly) on the presence of gyrotropic configurations of the hypermagnetic field at the electroweak epoch. Over the intermediate frequency range the spectral energy density of the gravitational waves emitted by the hypermagnetic knots at the electroweak scale can exceed the inflationary signal even by nine orders of magnitude without affecting the standard bounds applicable on the stochastic backgrounds of gravitational radiation. The signal of hypermagnetic knots can be disambiguated, at least in principle, since the the produced gravitational waves are polarized.

    ↳ gr-qcastro-ph.COhep-phhep-thClass.Quant.Grav.(2017)·6 citations
22. 22*

    Study of charged particle production in $U$-$U$ collisions in a Wounded Quark Model

    O. S. K. Chaturvedi🇮🇳 · P. K. Srivastava🇮🇳 · Ashwini Kumar🇮🇳 · B. K. Singh🇮🇳

    Recently, there has been a growing interest in the study of deformed uranium-uranium ($U$-$U$) collisions in its various geometrical configurations due to their usefulness in understanding the different aspects of quantum chromodynamics (QCD). In this paper we have studied the particle production in deformed $U$-$U$ collisions at $\sqrt{s_{NN}}$ = $193$ GeV using modified wounded quark model (WQM). At first, we have shown the variation of quark-nucleus inelastic scattering cross-section (${\sigma }_{qA}^{in}$) with respect to centralities for various geometrical orientations of $U$-$U$ collisions in WQM. After that we have calculated the pseudorapidity density ($d{n}_{ch}/d\eta$) within WQM using two-component prescription. Further we have calculated the transverse energy density distribution ($d{E}_T/d\eta$) along with the ratio of transverse energy to charged hadron multiplicity ($E_T/N_{ch}$) for $U$-$U$ collisions and compared them with the corresponding experimental data. We have shown the scaling behavior of $d{n}_{ch}/d\eta$ and $d{E}_T/d\eta$ for different initial geometry of $U$-$U$ collision with respect to $p$-$p$ data at $\sqrt{s_{NN}}=200$ GeV. Furthermore we have shown the Bjorken energy density achieved in $U$-$U$ collisions for various configurations and compared them with experimental data of $Au$-$Au$ at 200 GeV. We observe that the present model suitably describes the experimental data for minimum bias geometrical configuration of $U$-$U$ collisions. An estimate for various observables in different initial geometries of $U$-$U$ collisions is also presented which will be tested in future by experimental data.

    ↳ nucl-thhep-phEur.Phys.J.Plus(2017)·9 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.