Conceptual Design for a Polarized Proton-Antiproton Collider Facility at Gsi

Two possible options of polarized proton-antiproton collider at the future HESR storage ring are considered. It is shown that the modifications of the present HESR project which are needed to arrange for the polarized proton-antiproton collisions are relatively moderate. An achievable luminosity of 5x10^31 cm^-2 sec^-1 will provide a possibility to carry out experiments in the CM energy range 10-30 GeV, a particularly interesting option for Drell-Yan physics

Nonthermal two component dark matter model for Fermi-LAT γ -ray excess and 3.55 keV X-ray line

A two component model of nonthermal dark matter is formulated to simultaneously explain the Fermi-LAT results indicating a γ -ray excess observed from our Galactic Centre in the 1–3 GeV energy range and the detection of an X-ray line at 3.55 keV from extragalactic sources. Two additional Standard Model singlet scalar fields S 2 and S 3 are introduced. These fields couple among themselves and with the Standard Model Higgs doublet H . The interaction terms among the scalar fields, namely H , S 2 and S 3 , are constrained by the application of a discrete ℤ 2  × ℤ 2 ′ symmetry which breaks softly to a remnant ℤ 2 ′ ′ symmetry. This residual discrete symmetry is then spontaneously broken through an MeV order vacuum expectation value u of the singlet scalar field S 3 . The resultant physical scalar spectrum has the Standard Model like Higgs as χ 1 with M χ 1 ∼ 125 $${M}_{\chi_1}\sim 125$$ GeV, a moderately heavy scalar χ 2 with 50 GeV ≤ M χ 2 ≤ 80 $${M}_{\chi_2}\le 80$$ GeV and a light χ 3 with M χ 3 ∼ 7 $${M}_{\chi_3}\sim 7$$ keV. There is only tiny mixing between χ 1 and χ 2 as well as between χ 1 and χ 3 . The lack of importance of domain wall formation in the present scenario from the spontaneous breaking of the discrete symmetry ℤ 2 ′ ′ , provided u ≤ 10 MeV, is pointed out. We find that our proposed two component dark matter model is able to explain successfully both the above mentioned phenomena — the Fermi-LAT observed γ -ray excess (from the χ 2 → b b ¯ $${\chi}_2\to \mathrm{b}\overline{\mathrm{b}}$$ decay mode) and the observation of the X-ray line (from the decay channel χ 3 → γγ ) by the XMM-Newton observatory

Application of TauSpinner for Studies on τ\tau -Lepton Polarization and Spin Correlations in ZZ, WW and HH Decays at the LHC

The $\tau$ lepton plays an important role in the physics program at the Large Hadron Collider. Spin of the $\tau$ lepton represents an interesting phenomenological quantity which can be used for separation of signal from background in searches for New Physics processes or in measuring properties of New Particles decaying to $\tau$ leptons. A proper treatment of $\tau$~spin effects in the Monte Carlo simulations is important for understanding the detector acceptance and for measurements of $\tau$ polarization and $\tau$ spin correlations. The {\sf TauSpinner} package is a software tool allowing to modify $\tau$ spin effects in any event sample containing $\tau$ leptons. By calculating spin weights, attributed on the event-by-event basis, it enables numerical evaluation and/or modification of the spin effects on experimentally measured distributions. We review a selection of simple distributions which can be used to monitor longitudinal spin effects in $\tau$ decays. New methods, with respect to previous publications, for validation of spin content of the user-prepared event sample are provided

Final analysis of KEDR data on J/ψ and ψ(2S) masses

We present the analysis of all KEDR data on the determination of J/ψ and ψ(2S) masses. The data comprise six scans of J/ψ and seven scans of ψ(2S) which were performed at the VEPP-4M e+e− collider in 2002–2008. The beam energy was determined using the resonance depolarization method. The detector and accelerator conditions during scans were very different that increases the reliability of the averaged results. The analysis accounts for partial correlations of systematic uncertainties on the masses. The following mass values were obtained: MJ/ψ=3096.900±0.002±0.006 MeV,Mψ(2S)=3686.099±0.004±0.009 MeV. These results supersede our previous measurements published in 2003 and 2012

Probing the short range spin dependent interactions by polarized 3 He atom beams

Experiments using polarized 3 He atom beams to search for short range spin dependent forces are proposed. High intensity, high polarization, small beam size 3 He atom beams have been successfully produced and used in surface science researches. By incorporating background reduction designs as combination shielding by μ -metal and superconductor and double beam paths, the precision of spin rotation angle per unit length could be improved by a factor of ∼104 . By this precision, in combination with a high density and low magnetic susceptibility sample source mass, and reversing one beam path if necessary, sensitivities on three different types of spin dependent interactions could be improved by as much as ∼102 to ∼108 over the current experiments at the millimeter range

Inner-most stable circular orbits in extremal and non-extremal Kerr–Taub-NUT spacetimes

We study causal geodesics in the equatorial plane of the extremal Kerr–Taub-NUT spacetime, focusing on the inner-most stable circular orbit (ISCO), and we compare its behavior with extant results for the ISCO in the extremal Kerr spacetime. Calculations of the radii of the direct ISCO, its Kepler frequency, and the rotational velocity show that the ISCO coincides with the horizon in the exactly extremal situation. We also study geodesics in the strong non -extremal limit, i.e., in the limit of a vanishing Kerr parameter (i.e., for Taub-NUT and massless Taub-NUT spacetimes as special cases of this spacetime). It is shown that the radius of the direct ISCO increases with NUT charge in Taub-NUT spacetime. As a corollary, it is shown that there is no stable circular orbit in massless NUT spacetimes for timelike geodesics

Reducing differential equations for multiloop master integrals

We present an algorithm of the reduction of the differential equations for master integrals the Fuchsian form with the right-hand side matrix linearly depending on dimensional regularization parameter ϵ . We consider linear transformations of the functions column which are rational in the variable and in ϵ . Apart from some degenerate cases described below, the algorithm allows one to obtain the required transformation or to ascertain irreducibility to the form required. Degenerate cases are quite anticipated and likely to correspond to irreducible systems

Production of two charm quark–antiquark pairs in single-parton scattering within the kt -factorization approach

We present first results for the 2→4 single-parton scattering gg→cc¯cc¯ subprocess for the first time fully within the kt -factorization approach. In this calculation we have used the Kimber–Martin–Ryskin unintegrated gluon distribution which effectively includes some class of higher-order gluon emissions, and an off-shell matrix element squared calculated using recently developed techniques. The results are compared with our earlier result obtained within the collinear-factorization approach. Only slightly larger cross sections are obtained than in the case of the collinear approach. Inclusion of transverse momenta of gluons entering the hard process leads to a much stronger azimuthal decorrelation between cc and c¯c¯ than in the collinear-factorization approach. A comparison to predictions of double parton scattering (DPS) results and the LHCb data strongly suggests that the assumption of two fully independent DPS ( gg→cc¯⊗gg→cc¯ ) may be too approximate

Primary Energy Measurement with EAS Cherenkov Light: Experiment QUEST and CORSIKA Simulation

A new primary mass independent method of energy measurement has been developed by exploiting: a) the joint analysis of the shower size, obtained by EAS-TOP, and of the EAS atmospheric Cherenkov light lateral distribution, obtained by the QUEST array, and b) simulations based on the CORSIKA/QGSJET code. The method is based on the correlation between the size/energy ratio and the steepness of Cherenkov light lateral distribution and has been compared with a "classical" one based on the Cherenkov light flux at a fixed distance (175 m) from the EAS core. An absolute energy calibration of the EAS atmospheric Cherenkov light flux has been obtained

Space-like D p branes: accelerating cosmologies versus conformally de Sitter space-time

We consider the space-like D p brane solutions of type II string theories having isometries ISO( p + 1) × SO(8 − p, 1). These are asymptotically flat solutions or in other words, the metrics become flat at the time scale τ ≫ τ 0 . On the other hand, when τ ∼ τ 0 , we get ( p + 1) + 1 dimensional flat FLRW metrics upon compactification on a (8 − p ) dimensional hyperbolic space with time dependent radii. We show that the resultant ( p + 1) + 1 dimensional metrics describe transient accelerating cosmologies for all p from 1 to 6, i.e., from (2+1) to (7+1) space-time dimensions. We show how the accelerating phase changes with the interplay of the various parameters characterizing the solutions in (3 + 1) dimensions. Finally, for τ ≪ τ 0 , after compactification on (8 − p ) dimensional hyperbolic space, the resultant metrics are shown to take the form of ( p + 1) + 1 dimensional de Sitter spaces upto a conformal transformation. Cosmologies here are decelerating, but, only in a particular conformal frame we get eternal acceleration