125747217
NEXT, a HPXe TPC for neutrinoless double beta decay searches
The next-generation experiments for neutrinoless double b eta decay searches are a major challenge, since the detectors have to fulfill conflicting requir ements: they have to be very massive and scalable; very sensitive to the signature of the β β processes, and simultaneously impose extremely stringent limits on the copious backgrounds. A high-pressure gaseous Xenon TPC may be the ideal detector f or this purpose: the isotope 136Xe is almost 9% of natural Xenon and enrichment by centrifugati on is a relatively easy technology as demonstrated by the EXO collaboration; the detector can be e xtrapolated to large masses; energy resolution in gas is expected to be at the level of 1% FWHM at Qβ β ; this fact, combined with the very long life of theβ β 2ν mode accounts for negligible backgrounds of intrinsic orig in up to masses of the order of 1 ton. The detector is fully active an d the gas can be continuously re-circulated and purified, which, together with the existe nce of a kinematical signature gives an extra handle against backgrounds. NEXT (Neutrino Experiment with a Xenon TPC) is an on-going pr oject that aims to build a 100 kg HPXe TPC at a pressure of ∼10 bar. The experiment has already been aproved by the scient ifi committee of the Canfranc Underground Laboratory (LSC), in Spain, for the initial R&D phase. The NEXT Collaboration has defined an ambitious roadmap for t he next five years: an initial phase of R&D during 2 years will be used to decide the technolo gy (MicroMegas, GEMs, APDs, PMTs, etc.); in 3 years a first prototype (NEXT-10) will be con structed; followed by NEXT-100 in 5 years. A special grant (Consolider-Ingenio 2010) from t he Ministry of Science of Spain will fund the experiment during this period. The Collaboration i s composed by the leading Spanish groups in experimental neutrino and underground physics. The general ideas behind neutrinoless double beta decay sea rches with a HPXe TPC are discussed in this note.
122106372
Forward pi+/- production in p-O(2) and p-N(2) interactions at 12-GeV/c
Measurements of double-differential charged pion production cross-sections in interactions of 12 GeV/c protons on O2 and N2 thin targets are presented in the kinematic range 0.5 GeV/c ⩽pπ<8 GeV/c and 50 mrad ⩽θπ<250 mrad (in the laboratory frame) and are compared with p–C results. For p–N2 (p–O2) interactions the analysis is performed using 38576 (7522) reconstructed secondary pions. The analysis uses the beam instrumentation and the forward spectrometer of the HARP experiment at CERN PS. The measured cross-sections have a direct impact on the precise calculation of atmospheric neutrino fluxes and on the improved reliability of extensive air shower simulations by reducing the uncertainties of hadronic interaction models in the low energy range. In particular, the present results allow the common hypothesis that p–C data can be used to predict the p–N2 and p–O2 pion production cross-sections to be tested
119196633
Results of the material screening program of the NEXT experiment
The 'Neutrino Experiment with a Xenon TPC (NEXT)', intended to investigate neutrinoless double beta decay, requires extremely low background levels. An extensive material screening and selection process to assess the radioactivity of components is underway combining several techniques, including germanium gamma-ray spectrometry performed at the Canfranc Underground Laboratory; recent results of this material screening program are presented here.
53333389
Radiopurity assessment of the tracking readout for the NEXT double beta decay experiment
The ``Neutrino Experiment with a Xenon Time-Projection Chamber'' (NEXT) is intended to investigate the neutrinoless double beta decay of 136Xe, which requires a severe suppression of potential backgrounds; therefore, an extensive screening and selection process is underway to control the radiopurity levels of the materials to be used in the experimental set-up of NEXT. The detector design combines the measurement of the topological signature of the event for background discrimination with the energy resolution optimization. Separate energy and tracking readout planes are based on different sensors: photomultiplier tubes for calorimetry and silicon multi-pixel photon counters for tracking. The design of a radiopure tracking plane, in direct contact with the gas detector medium, was specially challenging since the needed components like printed circuit boards, connectors, sensors or capacitors have typically, according to available information in databases and in the literature, activities too large for experiments requiring ultra-low background conditions. Here, the radiopurity assessment of tracking readout components based on gamma-ray spectroscopy using ultra-low background germanium detectors at the Laboratorio Subterraaneo de Canfranc (Spain) is described. According to the obtained results, radiopure enough printed circuit boards made of kapton and copper, silicon photomultipliers and other required components, fulfilling the requirement of an overall background level in the region of interest of at most 8×10−4 counts keV−1 kg−1 y−1, have been identified.
122699398
Forward production of charged pions with incident pi(+/-) on nuclear targets measured at the CERN PS
Abstract Measurements of the double-differential π ± production cross-section in the range of momentum 0.5 GeV / c ⩽ p ⩽ 8.0 GeV / c and angle 0.025 rad ⩽ θ ⩽ 0.25 rad in interactions of charged pions on beryllium, carbon, aluminium, copper, tin, tantalum and lead are presented. These data represent the first experimental campaign to systematically measure forward pion hadroproduction. The data were taken with the large acceptance HARP detector in the T9 beam line of the CERN PS. Incident particles, impinging on a 5% nuclear interaction length target, were identified by an elaborate system of beam detectors. The tracking and identification of the produced particles was performed using the forward spectrometer of the HARP detector. Results are obtained for the double-differential cross-sections d 2 σ / d p d Ω mainly at four incident pion beam momenta (3 GeV/ c , 5 GeV/ c , 8 GeV/ c and 12 GeV/ c ). The measurements are compared with the GEANT4 and MARS Monte Carlo simulation.
109935636
Comparison of large-angle production of charged pions with incident protons on cylindrical long and short targets
We gratefully acknowledge the help and support of the PS beam staff and of the numerous technical collaborators who contributed to the detector design, construction, commissioning and operation. In particular, we would like to thank G. Barichello, R. Brocard, K. Burin, V. Carassiti, F. Chignoli, D. Conventi, G. Decreuse, M. Delattre, C. Detraz, A. Domeniconi, M. Dwuznik, F. Evangelisti, B. Friend, A. Iaciofano, I. Krasin, D. Lacroix, J.-C. Legrand, M. Lobello, M. Lollo, J. Loquet, F. Marinilli, J. Mulon, L. Musa, R. Nicholson, A. Pepato, P. Petev, X. Pons, I. Rusinov, M. Scandurra, E. Usenko, and R. van der Vlugt, for their support in the construction of the detector. The collaboration acknowledges the major contributions and advice of M. Baldo-Ceolin, L. Linssen, M.T. Muciaccia and A. Pullia during the construction of the experiment. The collaboration is indebted to V. Ableev, P. Arce, F. Bergsma, P. Binko, E. Boter, C. Buttar, M. Calvi, M. Campanelli, C. Cavion, A. Chukanov, A. De Min, M. Doucet, D. Dullmann, R. Engel, V. Ermilova, W. Flegel, P. Gruber, Y. Hayato, P. Hodgson, A. Ichikawa, I. Kato, O. Klimov, T. Kobayashi, D. Kustov, M. Laveder, M. Mass, H. Meinhard, T. Nakaya, K. Nishikawa, M. Paganoni, F. Paleari, M. Pasquali, J. Pasternak, C. Pattison, M. Placentino, S. Robbins, G. Santin, V. Serdiouk, S. Simone, A. Tornero, S. Troquereau, S. Ueda, A. Valassi, F. Vannucci and K. Zuber for their contributions to the experiment and to P. Dini for help in MC production. 
We acknowledge the contributions of V. Ammosov, G. Chelkov, D. Dedovich, F. Dydak, M. Gostkin, A. Guskov, D. Khartchenko, V. Koreshev, Z. Kroumchtein, I. Nefedov, A. Semak, J. Wotschack, V. Zaets and A. Zhemchugov to the work described in this paper. 
The experiment was made possible by grants from the Institut Interuniversitaire des Sciences Nucleaires and the Interuniversitair Instituut voor Kernwetenschappen (Belgium), Ministerio de Educacion y Ciencia, Grant FPA2003-06921-c02-02 and Generalitat Valenciana, grant GV00-054-1, CERN (Geneva, Switzerland), the German Bundesministerium fur Bildung und Forschung (Germany), the Istituto Nazionale di Fisica Nucleare (Italy), INR RAS (Moscow), the Russian Foundation for Basic Research (grant 08-02-00018) and the Particle Physics and Astronomy Research Council (UK). We gratefully acknowledge their support. This work was supported in part by the Swiss National Science Foundation and the Swiss Agency for Development and Cooperation in the framework of the programme SCOPES - Scientific co-operation between Eastern Europe and Switzerland.
13215290
Constraints on the redshift dependence of the dark energy potential
We develop a formalism to characterize the shape and the redshift evolution of the dark energy potential. Our formalism makes use of quantities similar to the horizon-flow parameters in inflation and is general enough that can deal with multiscalar quintessence scenarios, exotic matter components, and higher-order curvature corrections to General Relativity. We show how the shape of the dark energy potential can be recovered nonparametrically using this formalism and we present approximations analogous to the ones relevant to slow-roll inflation. Since presently available data do not allow a nonparametric and exact reconstruction of the potential, we consider a general parametric description. This reconstruction can also be used in other approaches followed in the literature (e.g., the reconstruction of the redshift evolution of the dark energy equation of state $w(z)$). Using observations of passively evolving galaxies and supernova data we derive constraints on the dark energy potential shape in the redshift range $0.1lzl1.8$. Our findings show that at the $1\ensuremath{\sigma}$ level the potential is consistent with being constant, although at the same level of confidence variations cannot be excluded with current data. We forecast constraints achievable with future data from the Atacama Cosmology Telescope.
119227318
Topology from cosmology
We show that cosmological observables can constrain the topology of the compact additional dimensions predicted by string theory. To do this, we develop a general strategy for relating cosmological observables to the microscopic parameters of the potentials and field-dependent kinetic terms of the multiple scalar fields that arise in the low-energy limit of string theory. We apply this formalism to the Large Volume Scenarios in Type IIB flux compactifications where analytical calculations are possible. Our methods generalize to other settings.
3214344
A multi-boundary AdS orbifold and DLCQ holography: a universal holographic description of extremal black hole horizons
We examine a stationary but non-static asymptotically AdS3 spacetime with two causally connected conformal boundaries, each of which is a ``null cylinder'', namely a cylinder with a null direction identified. This spacetime arises from three different perspectives: (i) as a non-singular, causally regular orbifold of global AdS3 by boosts, (ii) as a Penrose-like limit focusing on the horizon of extremal BTZ black holes, and (iii) as an S1 fibration over AdS2. Each of these perspectives sheds an interesting light on holography. Examination of the conformal boundary of the spacetime shows that the dual to the space should involve DLCQ limits of the D1-D5 conformal field theory. The Penrose-like limit approach leads to a similar conclusion, by isolating a sector of the complete D1-D5 CFT that describes the physics in the vicinity of the horizon of an extremal black hole. As such this is a holographic description of the universal horizon dynamics of the extremal black holes in AdS3 and also of the four and five dimensional stringy black holes whose states were counted in string theory. The AdS2 perspective draws a connection to a 0+1d quantum mechanical theory. Various dualities lead to a Matrix model description of the spacetime. Many interesting issues that are related to both de Sitter physics and attempts to ``see behind a horizon'' using AdS/CFT arise from (a) the presence of two disconnected components to the boundary, and (b) the analytic structure of bulk physics in the complex coordinate plane.
122340661
Wave operators and analytic solutions for systems of non-linear Klein-Gordon equations and of non-linear Schrödinger equations
We consider, in a 1+3 space time, arbitrary (finite) systems of nonlinear Klein-Gordon equations (respectively Schrödinger equations) with an arbitrary local and analytic non-linearity in the unknown and its first and second order space-time (respectively first order space) derivatives, having no constant or linear terms. No restriction is given on the frequency sign of the initial data. In the case of non-linear Klein-Gordon equations all masses are supposed to be different from zero.We prove, for such systems, that the wave operator (fromt=∞ tot=0) exists on a domain of small entire test functions of exponential type and that the analytic Cauchy problem, in ℝ+×ℝ3, has a unique solution for each initial condition (att=0) being in the image of the wave operator. The decay properties of such solutions are discussed in detail.
29221858
Time travel on a string