Supersymmetric gauge theories on five-manifolds

We construct rigid supersymmetric gauge theories on Riemannian five-manifolds. We follow a holographic approach, realizing the manifold as the conformal boundary of a six-dimensional bulk supergravity solution. This leads to a systematic classification of five-dimensional supersymmetric backgrounds with gravity duals. We show that the background metric is furnished with a conformal Killing vector, which generates a transversely holomorphic foliation with a transverse Hermitian structure. Moreover, we prove that any such metric defines a supersymmetric background. Finally, we construct supersymmetric Lagrangians for gauge theories coupled to arbitrary matter on such backgrounds.Comment: 35 pages: v2: minor corrections and references added. Published versio

Theoretical uncertainties in extracting cosmic-ray diffusion parameters: the boron-to-carbon ratio

PAMELA and, more recently, AMS-02, are ushering us into a new era of greatly reduced statistical uncertainties in experimental measurements of cosmic-ray fluxes. In particular, new determinations of traditional diagnostic tools such as the boron-to-carbon ratio (B/C) are expected to significantly reduce errors on cosmic-ray diffusion parameters, with important implications for astroparticle physics, ranging from inferring primary source spectra to indirect dark matter searches. It is timely to stress, however, that the conclusions obtained crucially depend on the framework in which the data are interpreted as well as from some nuclear input parameters. We aim at assessing the theoretical uncertainties affecting the outcome, with models as simple as possible while still retaining the key dependencies. We compare different semi-analytical, two-zone model descriptions of cosmic-ray transport in the Galaxy. We test for the effect of a primary source contamination in the boron flux by parametrically altering its flux, as well as for nuclear cross section uncertainties. Our study on preliminary results from AMS-02 suggests that, differently for instance from the leptonic case, realistic modelling of the geometry of the Galaxy and of the source distribution are of minor importance to correctly reproduce B/C data at high energies and thus, to a large extent, for the extraction of diffusion parameters. The Ansatz on the lack of primary injection of boron represents the most serious bias, and requires multi-messenger studies to be addressed. If this uncertainty could be lifted, nuclear uncertainties would still represent a serious concern, which degrade the systematic error on the inferred parameters to the 20% level, or three times the estimated experimental sensitivity. In order to reduce this, a new nuclear cross section measurement campaign is probably required.Comment: 14 pages, 11 figures, 4 tables, published in A&

AMS-02 antiprotons, at last! Secondary astrophysical component and immediate implications for Dark Matter

Using the updated proton and helium fluxes just released by the AMS-02 experiment we reevaluate the secondary astrophysical antiproton to proton ratio and its uncertainties, and compare it with the ratio preliminarly reported by AMS-02. We find no unambiguous evidence for a significant excess with respect to expectations. Yet, some preference for a flatter energy dependence of the diffusion coefficient starts to emerge. Also, we provide a first assessment of the room left for exotic components such as Galactic Dark Matter annihilation or decay, deriving new stringent constraints.Comment: 12 pages, 5 figures; Comments and clarifications added (including an appendix), matches version published on JCA

A large dynamic range integrated front-end for photomultiplier tubes

A full custom analog CMOS circuit for obtaining a photomultiplier readout with a 16 bit resolution over 7 V has been developed. It is part of the R&D program for the photomultiplier tube front-end readout of the Pierre Auger Observatory northern site. It performs signal duplication and amplification with three gains: 0.15, 1 and 6. Each amplifier has a resolution of 10 bit and can measure signals with durations of several microseconds with a good baseline stability, for an input charge of up to tens of nano-Coulombs. The amplification is performed by current feedback amplifiers with a bandwidth of 60 MHz.The input impedance, adapted to the coaxial cables, is stable over the whole working range. A prototype was submitted in April 2004 and successfully tested. The linearity over the working range is less than 1%. It was also successfully tested on the Auger surface detector element installed at Orsay (comprised of a Cherenkov water tank equipped with Photonis XP1805 9” diameter photomultiplier tubes). The resolution over 7 V is 16.6 bit.This circuit is the first step towards a “system-on-a-chip” (SoC) solution for a photomultplier tube readout equipped with a fast ADC for signal digitization. A setup using a single cable for both the signal and the photomultiplier high voltage power supply was shown to be successful

Simulation of large photomultipliers for experiments in astroparticle physics

We have developed an accurate simulation model of the large 9 inch photomultiplier tubes (PMT) used in water-Cherenkov detectors of cosmic-ray induced extensive air-showers. This work was carried out as part of the development of the Offline simulation software for the Pierre Auger Observatory surface array, but our findings may be relevant also for other astrophysics experiments that employ similar large PMTs. The implementation is realistic in terms of geometrical dimensions, optical processes at various surfaces, thin-film treatment of the photocathode, and photon reflections on the inner structure of the PMT. With the quantum efficiency obtained for this advanced model we have calibrated a much simpler and a more rudimentary model of the PMT which is more practical for massive simulation productions. We show that the quantum efficiency declared by manufactures of the PMTs is usually determined under conditions substantially different from those relevant for the particular experiment and thus requires careful (re)interpretation when applied to the experimental data or when used in simulations. In principle, the effective quantum efficiency could vary depending on the optical characteristics of individual events.Comment: 8 pages, 11 figure

Prospectives for A Fixed-Target ExpeRiment at the LHC: AFTER@LHC

We argue that the concept of a multi-purpose fixed-target experiment with the proton or lead-ion LHC beams extracted by a bent crystal would offer a number of ground-breaking precision-physics opportunities. The multi-TeV LHC beams will allow for the most energetic fixed-target experiments ever performed. The fixed-target mode has the advantage of allowing for high luminosities, spin measurements with a polarised target, and access over the full backward rapidity domain --uncharted until now-- up to x_F ~ -1.Comment: 6 pages, 1 table, LaTeX. Proceedings of the 36th International Conference on High Energy Physics (ICHEP2012), 4-11 July 2012, Melbourne, Australi

MPGD's spatial and energy resolution studies with an adjustable point-like electron source

11th Vienna Conference on Instrumentation (February 2007) , to appear in the Proceedings (NIM A)International audienceMicropattern Gaseous Detectors (MPGD), like Micromegas or GEM, are used or foreseen in particle physics experiments for which a very good spatial resolution is required. We have developed an experimental method to separate the contribution of the transverse diffusion and the multiplication process by varying the number of primary electrons generated by a point-like source. A pulsed nitrogen laser is focused by an optical set-up on the drift electrode which is made of a thin metal layer deposited on a quartz lamina. The number of primary electrons can be adjusted from a few to several thousands on a spot which transverse size is less than $100 \mu m$ RMS. The detector can be positioned with an accuracy of $1\mu m$ by a motorized three dimensional system. This method was applied to a small Micromegas detector with a gain set between $10^3$ and $2.10^4$ and an injection of 60 to 2000 photoelectrons. Spatial resolutions as small as $5\mu m$ were measured with 2000 primary electrons. An estimation of the upper limit of the relative gain variance can be obtained from the measurements

Spin physics at A Fixed-Target ExpeRiment at the LHC (AFTER@LHC)

We outline the opportunities for spin physics which are offered by a next generation and multi-purpose fixed-target experiment exploiting the proton LHC beam extracted by a bent crystal. In particular, we focus on the study of single transverse spin asymetries with the polarisation of the target.Comment: Contributed to the 20th International Spin Physics Symposium, SPIN2012, 17-22 September 2012, Dubna, Russia, 4 pages, LaTe

A Fixed-Target ExpeRiment at the LHC (AFTER@LHC) : luminosities, target polarisation and a selection of physics studies

We report on a future multi-purpose fixed-target experiment with the proton or lead ion LHC beams extracted by a bent crystal. The multi-TeV LHC beams allow for the most energetic fixed-target experiments ever performed. Such an experiment, tentatively named AFTER for "A Fixed-Target ExperRiment", gives access to new domains of particle and nuclear physics complementing that of collider experiments, in particular at RHIC and at the EIC projects. The instantaneous luminosity at AFTER using typical targets surpasses that of RHIC by more than 3 orders of magnitude. Beam extraction by a bent crystal offers an ideal way to obtain a clean and very collimated high-energy beam, without decreasing the performance of the LHC. The fixed-target mode also has the advantage of allowing for spin measurements with a polarised target and for an access over the full backward rapidity domain up to xF ~ - 1. Here, we elaborate on the reachable luminosities, the target polarisation and a selection of measurements with hydrogen and deuterium targets.Comment: 6 pages. Proceedings of the Sixth International Conference on Quarks and Nuclear Physics QNP2012 (16-20 April 2012, Ecole Polytechnique, Palaiseau,France