APFELgrid: a high performance tool for parton density determinations

We present a new software package designed to reduce the computational burden of hadron collider measurements in Parton Distribution Function (PDF) fits. The APFELgrid package converts interpolated weight tables provided by APPLgrid files into a more efficient format for PDF fitting by the combination with PDF and $\alpha_s$ evolution factors provided by APFEL. This combination significantly reduces the number of operations required to perform the calculation of hadronic observables in PDF fits and simplifies the structure of the calculation into a readily optimised scalar product. We demonstrate that our technique can lead to a substantial speed improvement when compared to existing methods without any reduction in numerical accuracy.Comment: 13 pages, 2 figures. Submitted to CPC. Code available from https://github.com/nhartland/APFELgri

Antiproton and Positron Signal Enhancement in Dark Matter Mini-Spikes Scenarios

The annihilation of dark matter (DM) in the Galaxy could produce specific imprints on the spectra of antimatter species in Galactic cosmic rays, which could be detected by upcoming experiments such as PAMELA and AMS02. Recent studies show that the presence of substructures can enhance the annihilation signal by a "boost factor" that not only depends on energy, but that is intrinsically a statistical property of the distribution of DM substructures inside the Milky Way. We investigate a scenario in which substructures consist of $\sim 100$ "mini-spikes" around intermediate-mass black holes. Focusing on primary positrons and antiprotons, we find large boost factors, up to a few thousand, that exhibit a large variance at high energy in the case of positrons and at low energy in the case of antiprotons. As a consequence, an estimate of the DM particle mass based on the observed cut-off in the positron spectrum could lead to a substantial underestimate of its actual value.Comment: 13 pages, 9 figures, minor changes, version accepted for publication in PR

Test of the gravitational redshift with stable clocks in eccentric orbits: application to Galileo satellites 5 and 6

The Einstein Equivalence Principle (EEP) is one of the foundations of the theory of General Relativity and several alternative theories of gravitation predict violations of the EEP. Experimental constraints on this fundamental principle of nature are therefore of paramount importance. The EEP can be split in three sub-principles: the Universality of Free Fall (UFF), the Local Lorentz Invariance (LLI) and the Local Position Invariance (LPI). In this paper we propose to use stable clocks in eccentric orbits to perform a test of the gravitational redshift, a consequence of the LPI. The best test to date was performed with the Gravity Probe A (GP-A) experiment in 1976 with an uncertainty of $1.4\times10^{-4}$. Our proposal considers the opportunity of using Galileo satellites 5 and 6 to improve on the GP-A test uncertainty. We show that considering realistic noise and systematic effects, and thanks to a highly eccentric orbit, it is possible to improve on the GP-A limit to an uncertainty around $(3-4)\times 10^{-5}$ after one year of integration of Galileo 5 and 6 data.Comment: 13 pages, 5 figures, accepted in Classical and Quantum Gravity as a Fast Track Communicatio

Statistical properties of the GALEX spectroscopic stellar sample

The GALEX General Data Release 4/5 includes 174 spectroscopic tiles, obtained from slitless grism observations, for a total of more than 60,000 ultraviolet spectra. We have determined statistical properties of the sample of GALEX stars. We have defined a suitable system of spectroscopic indices, which measure the main mid-UV features at the GALEX low spectral resolution and we have employed it to determine the atmospheric parameters of of stars in the range 4500<Teff<9000 K. Our preliminary results indicate that the sample is formed by a majority of main sequence F- and G-type stars, with metallicity [M/H]>-1 dex.Comment: 9 pages, 9 figures, accepted for publication in Astrophysics & Space Science, UV universe special issu

Neutron Measurements at the Lunar Surface (NMLS)

The Neutron Measurement System (NMS-Lunar) is an instrument payload manifested on Astrobotics Peregrine Mission One (M1). Astrobotic Mission One will land at Lacus Mortis (~44oN, 254oE). Astrobotic will fly up to fourteen NASA payloads to the lunar surface in addition to other payload customers on M1. NMS-Lunar is a re-design of the MSFC Fast Neutron Spectrometer (FNS) currently operating on the ISS. The design of NMS-Lunar enables operation on the lunar surface, integration onto the Peregrine lander, and measurement of thermal neutron count rates on the lunar surface. The primary science objectives for NMS-Lunar is to provide ground truth of mapped neutron data from the Lunar Reconnaissance Orbiter and Lunar Prospector missions. Neutrons are created when galactic cosmic rays interact with the lunar regolith, and can provide valuable elemental composition information

Probing the Nature of the Weakest Intergalactic Magnetic Fields with the High Energy Emission of Gamma-Ray Bursts

We investigate the delayed, secondary GeV-TeV emission of gamma-ray bursts and its potential to probe the nature of intergalactic magnetic fields. Geometrical effects are properly taken into account for the time delay between primary high energy photons and secondary inverse Compton photons from electron-positron pairs, which are produced in $\gamma$-$\gamma$ interactions with background radiation fields and deflected by intervening magnetic fields. The time-dependent spectra of the delayed emission are evaluated for a wide range of magnetic field strengths and redshifts. The typical flux and delay time of secondary photons from bursts at $z \sim 1$ are respectively $\sim 10^{-8}$ GeV cm$^{-2}$ s$^{-1}$ and $\sim 10^4$ s if the field strengths are $\sim 10^{-18}$ G, as might be the case in intergalactic void regions. We find crucial differences between the cases of coherent and tangled magnetic fields, as well as dependences on the field coherence length.Comment: 19 pages, 9 figures, formulation revised, accepted for publication in Ap

Systematic uncertainties in the determination of the local dark matter density

A precise determination of the local dark matter density and an accurate control over the corresponding uncertainties are of paramount importance for Dark Matter (DM) searches. Using very recent high-resolution numerical simulations of a Milky Way like object, we study the systematic uncertainties that affect the determination of the local dark matter density based on dynamical measurements in the Galaxy. In particular, extracting from the simulation with baryons the orientation of the Galactic stellar disk with respect to the DM distribution, we study the DM density for an observer located at $\sim$8 kpc from the Galactic center {\it on the stellar disk}, $\rho_0$. This quantity is found to be always larger than the average density in a spherical shell of same radius $\bar{\rho}_0$, which is the quantity inferred from dynamical measurements in the Galaxy, and to vary in the range $\rho_0/\bar{\rho}_0=1.01-1.41$. This suggests that the actual dark matter density in the solar neighbourhood is on average 21\% larger than the value inferred from most dynamical measurements, and that the associated systematic errors are larger than the statistical errors recently discussed in the literature.Comment: 6 pages, 3 figures, matches published versio

Handling and Transport of Oversized Accelerator Components and Physics Detectors

For cost, planning and organisational reasons, it is often decided to install large pre-built accelerators components and physics detectors. As a result surface exceptional transports are required from the construction to the installation sites. Such heavy transports have been numerous during the LHC installation phase. This paper will describe the different types of transport techniques used to fit the particularities of accelerators and detectors components (weight, height, acceleration, planarity) as well as the measurement techniques for monitoring and the logistical aspects (organisation with the police, obstacles on the roads, etc). As far as oversized equipment is concerned, the lowering into the pit is challenging, as well as the transport in tunnel galleries in a very scare space and without handling means attached to the structure like overhead travelling cranes. From the PS accelerator to the LHC, handling systems have been developed at CERN to fit with these particular working conditions. This paper will expose the operating conditions of the main transport equipments used at CERN in PS, SPS and LHC tunnels

The WIMP Forest: Indirect Detection of a Chiral Square

The spectrum of photons arising from WIMP annihilation carries a detailed imprint of the structure of the dark sector. In particular, loop-level annihilations into a photon and another boson can in principle lead to a series of lines (a WIMP forest) at energies up to the WIMP mass. A specific model which illustrates this feature nicely is a theory of two universal extra dimensions compactified on a chiral square. Aside from the continuum emission, which is a generic prediction of most dark matter candidates, we find a "forest" of prominent annihilation lines that, after convolution with the angular resolution of current experiments, leads to a distinctive (2-bump plus continuum) spectrum, which may be visible in the near future with the Fermi Gamma-Ray Space Telescope (formerly known as GLAST).Comment: 11 pages, 4 figure

The Abundance of New Kind of Dark Matter Structures

A new kind of dark matter structures, ultracompact minihalos (UCMHs) was proposed recently. They would be formed during the radiation dominated epoch if the large density perturbations are existent. Moreover, if the dark matter is made up of weakly interacting massive particles, the UCMHs can have effect on cosmological evolution because of the high density and dark matter annihilation within them. In this paper, one new parameter is introduced to consider the contributions of UCMHs due to the dark matter annihilation to the evolution of cosmology, and we use the current and future CMB observations to obtain the constraint on the new parameter and then the abundance of UCMHs. The final results are applicable for a wider range of dark matter parametersComment: 4 pages, 1 tabl