Fri·Apr 21, 2017Friday·April 21, 2017

1. 01*

   Constraints on axion-like particles and non-Newtonian gravity from measuring the difference of Casimir forces

   G. L. Klimchitskaya🇷🇺 · V. M. Mostepanenko🇷🇺

   We derive constraints on the coupling constants of axion-like particles to nucleons and on the Yukawa-type corrections to Newton's gravitational law from the results of recent experiment on measuring the difference of Casimir forces between a Ni-coated sphere and Au and Ni sectors of a structured disc. Over the wide range of axion masses from 2.61\,meV to 0.9\,eV the obtained constraints on the axion-to-nucleon coupling are up to a factor of 14.6 stronger than all previously known constraints following from experiments on measuring the Casimir interaction. The constraints on non-Newtonian gravity found here are also stronger than all that following from the Casimir and Cavendish-type experiments over the interaction range from 30\,nm to $5.4\mu$m. They are up to a factor of 177 stronger than the constraints derived recently from measuring the difference of lateral forces. Our constraints confirm previous somewhat stronger limits obtained from the isoelectronic experiment, where the contribution of the Casimir force was nullified.

   hep-phPRD(2017)·34 citations
2. 02*

   A bound state model for a light scalar

   Bob Holdom🇨🇦 · Roman Koniuk🇨🇦

   Recent lattice studies of near-conformal strong dynamics suggest the existence of a light scalar. This provides motivation to consider a simple Hamiltonian-based bound-state model where the pseudoscalar, scalar, vector and axial-vector states are treated on an equal footing. The model interpolates between the non-relativistic limit and the highly relativistic chiral limit, where the pseudoscalar mass drops to zero. The fermion mass becomes purely dynamical at this point. When the gauge coupling is constant over a moderate range of scales the scalar becomes significantly lighter than the spin 1 states as the chiral limit is approached. We relate this result to the behavior of the form factors of the respective states and their decay constants. In the conformal limit of the model all masses vanish and the theory is characterized by scaling dimensions.

   hep-phhep-latJHEP(2017)·3 citations
3. 03*

   Fluctuations of the gluon distribution from the small-x effective action

   Adrian Dumitru🇺🇸 · Vladimir Skokov🇺🇸

   The computation of observables in high energy QCD involves an average over stochastic semiclassical small-x gluon fields. The weight of various configurations is determined by the effective action. We introduce a method to study fluctuations of observables, functionals of the small-x fields, which does not explicitly involve dipoles. We integrate out those fluctuations of the gluon field under which a given observable is invariant. Thereby we obtain the effective potential for that observable describing its fluctuations about the saddle point. We determine explicitly the effective potential for the covariant gauge gluon distribution both for the McLerran-Venugopalan (MV) model and for a (non-local) Gaussian approximation for the small-x effective action. This provides insight into the correlation of fluctuations of the number of hard gluons versus their typical transverse momentum. We find that the spectral shape of the fluctuations of the gluon distribution is fundamentally different in the MV model, where there is a pile-up of gluons near the saturation scale, versus the solution of the small-x JIMWLK renormalization group, which generates essentially scale invariant fluctuations above the absorptive boundary set by the saturation scale.

   hep-phPRD(2017)·13 citations
4. 04*

   Light and compressed gluinos at the LHC via string theory

   S.S. AbdusSalam🇮🇷

   In this article, we show that making global fits of string theory model parameters to data is an interesting mechanism for probing, mapping and forecasting connections of the theory to real world physics. We considered a large volume scenario (LVS) with D3-branes matter fields and supersymmetry breaking. A global fit of the parameters to low energy data shows that the set of LVS models are associated with light gluinos which are quasi-degenerate with the neutralinos and charginos they can promptly decay into and thus possibly hidden to current LHC gluino search strategies.

   hep-phhep-exhep-thEPJC(2017)·0 citations
5. 05*

   Lepton flavor universality violation without new sources of quark flavor violation

   Jernej F. Kamenik🇸🇮 · Yotam Soreq🇺🇸 · Jure Zupan🇺🇸

   We show that new physics models without new flavor violating interactions can explain the recent anomalies in the $b\to s{\ell }^{+}{\ell }^{-}$ transitions. The $b\to s{\ell }^{+}{\ell }^{-}$ arises from a $Z^{\prime }$ penguin which automatically predicts the $V-A$ structure for the quark currents in the effective operators. This framework can be realized either in a renormalizable $U(1{)}^{\prime }$ setup or be due to new strongly interacting dynamics. The di-muon resonance searches at the LHC are becoming sensitive to this scenario since the $Z^{\prime }$ is relatively light, and could well be discovered in future searches by ATLAS and CMS.

   hep-phPRD(2018)·112 citations
6. 06*

   Electromagnetic decays of the neutral pion

   Esther Weil🇩🇪 · Gernot Eichmann🇩🇪 · Christian S. Fischer🇩🇪 · Richard Williams🇩🇪

   We complement studies of the neutral pion transition form factor pi^0 --> gamma^(*) gamma^(*) with calculations for the electromagnetic decay widths of the processes pi^0 --> e^+ e^-, pi^0 --> e^+ e^- gamma and pi^0 --> e^+ e^- e^+ e^-. Their common feature is that the singly- or doubly-virtual transition form factor serves as a vital input that is tested in the non-perturbative low-momentum region of QCD. We determine this form factor from a well-established and symmetry-preserving truncation of the Dyson-Schwinger equations. Our results for the three- and four-body decays match results of previous theoretical calculations and experimental measurements. For the rare decay we employ a numerical method to calculate the process directly by deforming integration contours, which in principle can be generalized to arbitrary integrals as long as the analytic structure of the integrands are known. Our result for the rare decay is in agreement with dispersive calculations but still leaves a 2 sigma discrepancy between theory and experiment.

   hep-phhep-latnucl-thPRD(2017)·65 citations
7. 07*

   A hybrid setup for fundamental unknowns in neutrino oscillations using T2HK ($\nu$) and $\mu$-DAR ($\bar{\nu }$)

   Sanjib Kumar Agarwalla🇮🇳 · Monojit Ghosh🇯🇵 · Sushant K. Raut🇸🇪

   Neutrino mass hierarchy, CP-violation, and octant of ${\theta }_{23}$ are the fundamental unknowns in neutrino oscillations. In order to address all these three unknowns, we study the physics reach of a setup, where we replace the antineutrino run of T2HK with antineutrinos from muon decay at rest ($\mu$-DAR). This approach has the advantages of having higher statistics in both neutrino and antineutrino modes, and lower beam-on backgrounds for antineutrino run with reduced systematics. We find that a hybrid setup consisting of T2HK ($\nu$) and $\mu$-DAR ($\bar{\nu }$) in conjunction with full exposure from T2K and NO$\nu$A can resolve the issue of mass hierarchy at greater than 3$\sigma$ C.L. irrespective of the choices of hierarchy, ${\delta }_{\mathrm{CP}}$, and ${\theta }_{23}$. This hybrid setup can also establish the CP-violation at 5$\sigma$ C.L. for $\sim$ 55% choices of ${\delta }_{\mathrm{CP}}$, whereas the same for conventional T2HK ($\nu +\bar{\nu }$) setup along with T2K and NO$\nu$A is around 30%. As far as the octant of ${\theta }_{23}$ is concerned, this hybrid setup can exclude the wrong octant at 5$\sigma$ C.L. if ${\theta }_{23}$ is at least $3^{\circ }$ away from maximal mixing for any ${\delta }_{\mathrm{CP}}$.

   hep-phhep-exphysics.ins-detJHEP(2017)·15 citations
8. 08*

   Scale Invariance in Heavy Hadron Molecules

   Lisheng Geng🇨🇳 · Junxu Lu🇨🇳 · Manuel Pavon Valderrama🇨🇳

   We discuss a scenario in which the $P_c(4450{)}^{+}$ heavy pentaquark is a ${\Sigma }_c{\bar{D}}^{\ast }$-${\Lambda }_c(2595)\bar{D}$ molecule. The ${\Lambda }_{c1}\bar{D}\to {\Sigma }_c{\bar{D}}^{\ast }$ transition is mediated by the exchange of a pion almost on the mass shell that generates a long-range $1/r^2$ potential. This is analogous to the effective force that is responsible for the Efimov spectrum in three-boson systems interacting through short-range forces. The equations describing this molecule exhibit approximate scale invariance, which is anomalous and broken by the solutions. If the $1/r^2$ potential is strong enough this symmetry survives in the form of discrete scale invariance, opening the prospect of an Efimov-like geometrical spectrum in two-hadron systems. For a molecular pentaquark with quantum numbers ${\frac{3}{2}}^{-}$ the attraction is not enough to exhibit discrete scale invariance, but this prospect might very well be realized in a ${\frac{1}{2}}^{+}$ pentaquark or in other hadron molecules involving transitions between particle channels with opposite intrinsic parity and a pion near the mass shell. A very good candidate is the ${\Lambda }_c(2595){\bar{\Xi }}_b-{\Sigma }_c{\bar{\Xi }}_b^{\prime }$ molecule. Independently of this, the $1/r^2$ force is expected to play a very important role in the formation of this type of hadron molecule, which points to the existence of ${\frac{1}{2}}^{+}$ ${\Sigma }_c{D}^{\ast }$-${\Lambda }_c(2595)D$ and $1^{+}$ ${\Lambda }_c(2595){\Xi }_b-{\Sigma }_c{\Xi }_b^{\prime }$ molecules and $0^{+}$/$1^{-}$ ${\Lambda }_c(2595){\bar{\Xi }}_b-{\Sigma }_c{\bar{\Xi }}_b^{\prime }$ baryonia.

   hep-phnucl-thPRD(2018)·40 citations
9. 09*

   A New Light Particle in B Decays?

   Filippo Sala🇫🇷 · David M. Straub🇩🇪

   We investigate the possibility whether the tensions with SM expectations observed in several b -> sll transitions, including hints for lepton flavour non-universality, could be due to the decay of B into a new light resonance. We find that qualitative agreement with the data can be obtained with a light vector resonance dominantly decaying invisibly. This scenario predicts a shift in the muon anomalous magnetic moment that could explain the long-standing discrepancy. The most stringent constraint comes from searches for B decays with missing energy. A striking prediction is a strong q^2 dependence of the lepton flavour universality ratios R_K and R_K* that should allow to clearly confirm or rule out this possibility experimentally. We also comment on the possible connection of the invisible decay product with Dark Matter.

   hep-phPLB(2017)·87 citations
10. 10*

    Minimal flavor-changing $Z^{\prime }$ models and muon $g-2$ after the $R_{K^{\ast }}$ measurement

    Stefano Di Chiara🇪🇪 · Andrew Fowlie🇦🇺 · Sean Fraser🇪🇪 · Carlo Marzo🇪🇪 · Luca Marzola🇪🇪 · Martti Raidal🇪🇪 · Christian Spethmann🇪🇪

    There has been a steady interest in flavor anomalies and their global fits as ideal probes of new physics. If the anomalies are real, one promising explanation is a new $Z^{\prime }$ gauge boson with flavor-changing coupling to bottom and strange quarks and a flavor-conserving coupling to muons and, possibly, electrons. We point out that direct production of such a $Z^{\prime }$, emerging from the collision of $b$ and $s$ quarks, may offer a complementary window into these phenomena because collider searches already provide competitive constraints. On top of that, we analyse the same $Z^{\prime }$ scenario in relation to another long-standing discrepancy between theory and experiment that concerns the anomalous magnetic moment of the muon. By scanning the allowed $Z^{\prime }$ coupling strengths in the low-mass region, we assess the compatibility of the signals from LHCb with the $Z^{\prime }$ searches in the high energy LHC data and the measurements of the anomalous magnetic moment of the involved leptons. We also argue that observations of the latter can break the degeneracy pattern in the Wilson coefficients $C_9$ and $C_{10}$ presented by LHCb data. The $Z^{\prime }$ model we consider is compatible with the new measurement of $R_{K^{\ast }}$, therefore it can potentially account for the long-standing deviations observed in $B$-physics.

    hep-phNPB(2017)·71 citations
11. 11*

    Fradkin-Shenker Continuity and "Instead-of-Confinement" Phase

    M. Shifman🇺🇸 · A. Yung🇺🇸

    In 1979 Fradkin and Shenker observed \cite{Frad} that if one considers a Yang-Mills theory fully Higgsed by virtue of scalar fields in the fundamental representation of the $\mathrm{SU}(N)$ gauge group there is no phase transition in passing from the Higgs regime (weak coupling) to the "QCD confinement" regime at strong coupling. The above two regimes are continuously connected. We combine this observations with lessons from supersymmetric gauge theories which show that the Higgs phase is continuously connected to what is called "instead-of-confinement" phase rather than the phase with quark confinement. In the "instead-of-confinement" phase monopoles are confined and play a role of "constituent" quarks inside hadrons. In contrast, the Seiberg-Witten phase of quark confinement is not analytically connected to the Higgs phase. We propose dedicated lattice studies of Yang-Mills theories with scalar quarks.

    hep-phhep-thMod.Phys.Lett.A(2017)·4 citations
12. 12*

    Effect of emission of extra lepton pair for precise measurement of W-boson mass

    Sergii Antropov🇵🇱

    In the paper we present results for final state emissions of lepton pairs in decays of heavy intermediate states principally of Z boson, but of some importance for the W decays as well. The presented semi-analytical calculation and PHOTOS MC program are in numerical agreement to better than $5\%$ of pair effects. Suggestions for the future works are given.

    hep-phActa Phys.Polon.B(2017)·2 citations
13. 13*

    ${\sin }^2(\theta )w$ estimate and bounds on nonstandard interactions at source and detector in the solar neutrino low-energy regime

    Amir N. Khan🇨🇳 · Douglas W. McKay🇺🇸

    We explore the implications of the Borexino experiment's real time measurements of the lowest energy part of the neutrino spectrum from the primary pp fusion process up to 0.420 MeV through the 7^Be decay at 0.862 MeV to the pep reaction at 1.44 MeV. We exploit the fact that at such low energies, the large mixing angle solution to the Mikheyev-Smirnov-Wolfenstein matter effects in the sun are small for 7^Be and pep and negligible for pp. Consequently, the neutrinos produced in the sun change their flavor almost entirely through vacuum oscillations during propagation from the sun's surface and through possible nonstandard interactions acting at the solar source and Borexino detector. We combine the different NSI effects at source and detector in a single framework and use the current Borexino data to bound NSI non-universal and flavor- changing parameters at energies below the reach of reactor neutrino experiments. We also study the implication of the current data for the weak- mixing angle at this "low-energy frontier" data from the Borexino experiment, where it is expected to be slightly larger than its value at the Z mass. We find ${\sin }^2(\theta )w=0.224+-0.016$, the lowest energy-scale estimate to date. Looking to the future, we use projected sensitivities to solar neutrinos in next generation dedicated solar experiments and direct dark matter detection experiments and find a potential factor five improvement in determination of the weak-mixing angle and up to an order of magnitude improvement in probing the NSI parameters space.

    hep-phhep-exJHEP(2017)·27 citations
14. 14*

    Explaining the $R_K$ and $R_{K^{\ast }}$ anomalies

    Diptimoy Ghosh🇮🇱

    Recent LHCb results on $R_{K^{\ast }}$, the ratio of the branching fractions of $B\to K^{\ast }{\mu }^{+}{\mu }^{-}$ to that of $B\to K^{\ast }{e}^{+}{e}^{-}$, for the dilepton invariant mass bins $q^2\equiv m_{\ell \ell }^2=[0.045-1.1]$ GeV${}^2$ and $[1.1-6]$ GeV${}^2$ show approximately $2.5\sigma$ deviations from the corresponding Standard Model prediction in each of the bins. This, when combined with the measurement of $R_K(q^2=[1-6]\mathrm{Ge}{\mathrm{V}}^2)$, a similar ratio for the decay to a pseudo scalar meson, highly suggests for lepton non-universal new physics in semi-leptonic $B$ meson decays. In this work, we perform a model independent analysis of these potential new physics signals and identify the operators that do the best job in satisfying all these measurements. We show that heavy new physics, giving rise to $q^2$ independent local 4-Fermi operators of scalar, pseudo-scalar, vector or axial-vector type, is unable to explain all the three measurements simultaneously, in particular $R_{K^{\ast }}$ in the bin [0.045 - 1.1], within their experimental $1\sigma$ regions. We point out the possibility to explain $R_{K^{\ast }}$ in the low bin by an additional light ($\lesssim 20\mathrm{MeV}$) vector boson with appropriate coupling strengths to ($\bar{b}s$) and ($\bar{e}e$).

    hep-phhep-exEPJC(2017)·91 citations
15. 15*

    Casimir Meets Poisson: Improved Quark/Gluon Discrimination with Counting Observables

    Christopher Frye🇺🇸 · Andrew J. Larkoski🇺🇸 · Jesse Thaler🇺🇸 · Kevin Zhou🇺🇸

    Charged track multiplicity is among the most powerful observables for discriminating quark- from gluon-initiated jets. Despite its utility, it is not infrared and collinear (IRC) safe, so perturbative calculations are limited to studying the energy evolution of multiplicity moments. While IRC-safe observables, like jet mass, are perturbatively calculable, their distributions often exhibit Casimir scaling, such that their quark/gluon discrimination power is limited by the ratio of quark to gluon color factors. In this paper, we introduce new IRC-safe counting observables whose discrimination performance exceeds that of jet mass and approaches that of track multiplicity. The key observation is that track multiplicity is approximately Poisson distributed, with more suppressed tails than the Sudakov peak structure from jet mass. By using an iterated version of the soft drop jet grooming algorithm, we can define a "soft drop multiplicity" which is Poisson distributed at leading-logarithmic accuracy. In addition, we calculate the next-to-leading-logarithmic corrections to this Poisson structure. If we allow the soft drop groomer to proceed to the end of the jet branching history, we can define a collinear-unsafe (but still infrared-safe) counting observable. Exploiting the universality of the collinear limit, we define generalized fragmentation functions to study the perturbative energy evolution of collinear-unsafe multiplicity.

    hep-phhep-exJHEP(2017)·110 citations
16. 16*

    Shape of the acoustic gravitational wave power spectrum from a first order phase transition

    Mark Hindmarsh🇫🇮 · Stephan J. Huber🇬🇧 · Kari Rummukainen🇫🇮 · David J. Weir🇫🇮

    We present results from large-scale numerical simulations of a first order thermal phase transition in the early universe, in order to explore the shape of the acoustic gravitational wave and the velocity power spectra. We compare the results with the predictions of the recently proposed sound shell model. For the gravitational wave power spectrum, we find that the predicted $k^{-3}$ behaviour, where $k$ is the wavenumber, emerges clearly for detonations. The power spectra from deflagrations show similar features, but exhibit a steeper high-$k$ decay and an extra feature not accounted for in the model. There are two independent length scales: the mean bubble separation and the thickness of the sound shell around the expanding bubble of the low temperature phase. It is the sound shell thickness which sets the position of the peak of the power spectrum. The low wavenumber behaviour of the velocity power spectrum is consistent with a causal $k^3$, except for the thinnest sound shell, where it is steeper. We present parameters for a simple broken power law fit to the gravitational wave power spectrum for wall speeds well away from the speed of sound where this form can be usefully applied. We examine the prospects for the detection, showing that a LISA-like mission has the sensitivity to detect a gravitational wave signal from sound waves with an RMS fluid velocity of about $0.05c$, produced from bubbles with a mean separation of about $10^{-2}$ of the Hubble radius. The shape of the gravitational wave power spectrum depends on the bubble wall speed, and it may be possible to estimate the wall speed, and constrain other phase transition parameters, with an accurate measurement of a stochastic gravitational wave background.

    ↳ astro-ph.COhep-phPRD(2017)·591 citations
17. 17*

    Physics with ions at the Future Circular Collider

    David d'Enterria🇨🇭 · L. Apolinario🇵🇹 · N. Armesto🇪🇸 · A. Dainese🇮🇹 · J. Jowett🇨🇭 · J.P. Lansberg🇫🇷 · S. Masciocchi🇩🇪 · G. Milhano🇨🇭 · C. Roland🇨🇭 · C.A. Salgado🇪🇸 · M. Schaumann🇨🇭 · M. van Leeuwen🇨🇭 · U.A. Wiedemann🇨🇭

    The unique physics opportunities accessible with nuclear collisions at the CERN Future Circular Collider (FCC) are summarized. Lead-lead (PbPb) and proton-lead (pPb) collisions at $\sqrt{s_{NN}}$ = 39 and 63 TeV respectively with ${\mathcal{L}}_{int}$ = 33 nb${}^{-1}$ and 8 pb${}^{-1}$ monthly integrated luminosities, will provide unprecedented experimental conditions to study quark-gluon matter at temperatures $\mathcal{O}$(1 GeV). The following topics are succinctly discussed: (i) charm-quark densities thrice larger than at the LHC, leading to direct heavy-quark impact in the bulk QGP properties, (ii) quarkonia, including ${\rm Y}(1S)$, melting at temperatures up to five times above the QCD critical temperature, (iii) access to initial-state nuclear parton distributions (nPDF) at fractional momenta as low as $x\approx 10^{-7}$, (iv) availability of $5\cdot 10^5$ top-quark pairs per run to study the high-$x$ gluon nPDF and the energy loss properties of boosted colour-antennas, (v) study of possible Higgs boson suppression in the QGP, and (vi) high-luminosity $\gamma \gamma$ (ultraperipheral) collisions at c.m. energies up to 1 TeV.

    ↳ hep-exhep-phnucl-exnucl-thNPA(2017)·10 citations
18. 18*

    The QCD Equation of state and critical end-point estimates at $\mathcal{O}({\mu }_B^6)$

    Sayantan Sharma · for Bielefeld-BNL-CCNU collaboration

    We present results for the QCD Equation of State at non-zero chemical potentials corresponding to the conserved charges in QCD using Taylor expansion upto sixth order in the baryon number, electric charge and strangeness chemical potentials. The latter two are constrained by the strangeness neutrality and a fixed electric charge to baryon number ratio. In our calculations, we use the Highly Improved Staggered Quarks (HISQ) discretization scheme at physical quark masses and at different values of the lattice spacings to control lattice cut-off effects. Furthermore we calculate the pressure along lines of constant energy density, which serve as proxies for the freeze-out conditions and discuss their dependence on ${\mu }_B$ , which is necessary for hydrodynamic modelling near freezeout. We also provide an estimate of the radius of convergence of the Taylor series from the 6th order coefficients which provides a new constraint on the location of the critical end-point in the T-${\mu }_B$ plane of the QCD phase diagram.

    ↳ hep-lathep-phnucl-exnucl-thNPA(2017)·9 citations
19. 19*

    Constraining Anisotropic Lorentz Violation via the Spectral-Lag Transition of GRB 160625B

    Jun-Jie Wei🇨🇳 · Xue-Feng Wu🇨🇳 · Bin-Bin Zhang🇪🇸 · Lang Shao🇨🇳 · Peter Mészáros🇺🇸 · V. Alan Kostelecký🇺🇸

    Violations of Lorentz invariance can lead to an energy-dependent vacuum dispersion of light, which results in arrival-time differences of photons arising with different energies from a given transient source. In this work, direction-dependent dispersion constraints are obtained on nonbirefringent Lorentz-violating effects, using the observed spectral lags of the gamma-ray burst GRB 160625B. This burst has unusually large high-energy photon statistics, so we can obtain constraints from the true spectral time lags of bunches of high-energy photons rather than from the rough time lag of a single highest-energy photon. Also, GRB 160625B is the only burst to date having a well-defined transition from positive lags to negative lags, which provides a unique opportunity to distinguish Lorentz-violating effects from any source-intrinsic time lag in the emission of photons of different energy bands. Our results place comparatively robust two-sided constraints on a variety of isotropic and anisotropic coefficients for Lorentz violation, including first bounds on Lorentz-violating effects from operators of mass dimension ten in the photon sector.

    ↳ astro-ph.HEgr-qchep-phApJ(2017)·31 citations
20. 20*

    Extraction of HQE parameters from unquenched lattice data on pseudoscalar and vector heavy-light meson masses

    P. Gambino🇮🇹 · A. Melis🇪🇸 · S. Simula🇮🇹

    We present a precise lattice computation of pseudoscalar and vector heavy-light meson masses for heavy-quark masses ranging from the physical charm mass up to $\simeq 4$ times the physical b-quark mass. We employ the gauge configurations generated by the European Twisted Mass Collaboration (ETMC) with $N_f=2+1+1$ dynamical quarks at three values of the lattice spacing ($a\simeq 0.062,0.082,0.089$ fm) with pion masses in the range $M_{\pi }\simeq 210-450$ MeV. The heavy-quark mass is simulated directly on the lattice up to $\simeq 3$ times the physical charm mass. The interpolation to the physical $b$-quark mass is performed using the ETMC ratio method, based on ratios of the meson masses computed at nearby heavy-quark masses, and adopting the kinetic mass scheme. The extrapolation to the physical pion mass and to the continuum limit yields $m_b^{\mathrm{kin}}(1\text{mbox}GeV)=4.61(20)$ GeV, which corresponds to ${\overline{m}}_b({\overline{m}}_b)=4.26(18)$ GeV in the $\overline{MS}$ scheme. The lattice data are analyzed in terms of the Heavy Quark Expansion (HQE) and the matrix elements of dimension-4 and dimension-5 operators are extracted with a good precision, namely: $\overline{\Lambda }=0.552(26)$ GeV, ${\mu }_{\pi }^2=0.321(32)$ GeV${}^2$ and ${\mu }_G^2(m_b)=0.253(25)$ GeV${}^2$. The data also allow for a rough estimate of the dimension-6 operator matrix elements. As the HQE parameters play a crucial role in the inclusive determination of the Cabibbo-Kobayashi-Maskawa matrix elements $V_{ub}$ and $V_{cb}$, their precise determination on the lattice may eventually validate and improve the analyses based on fits to the semileptonic moments.

    ↳ hep-lathep-phPRD(2017)·69 citations
21. 21*

    Nuclear final-state interactions in deep inelastic scattering off the lightest nuclei

    W. Cosyn🇧🇪 · M. Sargsian🇺🇸

    We review recent progress in studies of nuclear final-state interactions in deep inelastic scattering (DIS) off the lightest nuclei tagged by a recoil nucleon. These processes hold a lot of potential for resolving the outstanding issues related to the dynamics of hadronization in QCD. Within the minimal Fock component framework, valid at large Bjorken $x$, the main features of the theoretical approach based on the virtual nucleon approximation are elaborated. In this approach, the strong final-state interaction of the DIS products with the nuclear fragments is described by an effective eikonal amplitude, whose parameters can be extracted from the analysis of semi-inclusive DIS off the deuteron target. The extraction of the $Q^2$ and $W$ mass dependences of these parameters gives a new observable in studying the QCD structure of DIS final states. Another important feature of tagged DIS off the lightest nuclei is the possibility of performing pole extrapolation with a high degree of accuracy. Such extrapolation allows an extraction of the neutron structure function in a model independent way due to suppression of the final-state interaction in the on-shell limit of the struck nucleon propagator. We review the first application of the pole extrapolation to recent experimental data. Finally, we outline the extension of the framework to inclusive DIS, including a polarized deuteron target as well as its application to the tagged DIS reactions for future experiments at fixed target and collider energies.

    ↳ nucl-thhep-phnucl-exIJMPE(2017)·18 citations
22. 22*

    Flavour composition and entropy increase of cosmological neutrinos after decoherence

    Daniel Boriero🇩🇪 · Dominik J. Schwarz🇩🇪 · Hermano Velten🇧🇷

    We propose that gravitational interactions of cosmic neutrinos with the statistically homogeneous and isotropic fluctuations of space-time leads to decoherence. This working hypothesis, which we describe by means of a Lindblad operator, is applied to the system of two- and three-flavour neutrinos undergoing vacuum oscillations and the consequences are investigated. As result of this decoherence we find that the neutrino entropy would increase as a function of initial spectral distortions, mixing angles and CP-violation phase. Subsequently we discuss the chances to discover such an increase observationally (in principle). We also present the expected flavour composition of the cosmic neutrino background after decoherence is completed. The physics of two- or three-flavour oscillation of cosmological neutrinos resembles in many aspects two- or three-level systems in atomic clocks, which were recently proposed by Weinberg for the study of decoherence phenomena.

    ↳ astro-ph.COhep-phUniverse(2019)·15 citations
23. 23*

    Final state interactions and the extraction of neutron single spin asymmetries from SIDIS by a transversely polarized ${}^3$He target

    A. Del Dotto🇮🇹 · L.P. Kaptari🇷🇺 · E. Pace🇮🇹 · G. Salmè🇮🇹 · S. Scopetta🇮🇹

    The semi-inclusive deep inelastic electron scattering off transversely polarized ${}^3$He, i.e. the process, $e+\overrightarrow{{}^3\mathrm{He}}\to e^{\prime }+h+X$, with $h$ a detected fast hadron, is studied beyond the plane wave impulse approximation. To this end, a distorted spin-dependent spectral function of a nucleon inside an A=3 nucleus is actually evaluated through a generalized eikonal approximation, in order to take into account the final state interactions between the hadronizing system and the (A-1) nucleon spectator one. Our realistic description of both nuclear target and final state is a substantial step forward for achieving a reliable extraction of the Sivers and Collins single spin asymmetries of the free neutron. To illustrate how and to what extent the model dependence due to the treatment of the nuclear effects is under control, we apply our approach to the extraction procedure of the neutron single spin asymmetries from those measured for ${}^3$He for values of the kinematical variables relevant both for forthcoming experiments at Jefferson Lab and, with an exploratory purpose, for the future Electron Ion Collider.

    ↳ nucl-thhep-phPRC(2017)·8 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.