Showing papers by "IFAE published in 2005"

Physics potential and experimental challenges of the LHC luminosity upgrade

Abstract: We discuss the physics potential and the experimental challenges of an upgraded LHC running at an instantaneous luminosity of 1035 cm-2s-1. The detector R&D needed to operate ATLAS and CMS in a very high radiation environment and the expected detector performance are discussed. A few examples of the increased physics potential are given, ranging from precise measurements within the Standard Model (in particular in the Higgs sector) to the discovery reach for several New Physics processes.

High energy (gamma)-ray emission from the starburst nucleus of NGC 253

Abstract: The high density medium that characterizes the central regions of starburst galaxies and its power to accelerate particles up to relativistic energies make these objects good candidates as {gamma}-rays sources. In this paper, a self-consistent model of the multifrequency emission of the starburst galaxy NGC 253, from radio to gamma-rays, is presented. The model is in agreement with all current measurements and provides predictions for the high energy behavior of the NGC 253 central region. Prospects for observations with the HESS array and GLAST satellite are especially discussed.

Study of the eta-eta' system in the two mixing angle scheme

Abstract: An analysis of various decay processes is performed using the two mixing angle description of the $\eta$-$\eta^\prime$ system, incorporating the link to the gluonic sector through anomalies. The agreement is excellent. For comparison with previous works, our results are expressed both in the ``octet-singlet'' and in the ``quark-flavour'' basis. It turns out that at the present experimental accuracy, the two angles are significantly different in the former, but not in the latter basis. The implications of our analysis for the Large $N_c$ $\chi$PT predictions are also discussed.

Rational foundation of GR in terms of statistical mechanic in the AdS/CFT framework

Abstract: In this article, we work out the microscopic statistical foundation of the supergravity description of the simplest 1/2 BPS sector in the AdS(5)/CFT(4). Then, all the corresponding supergravity observables are related to thermodynamical observables, and General Relativity is understood as a mean-field theory. In particular, and as an example, the Superstar is studied and its thermodynamical properties clarified.

Supersymmetry and electroweak breaking in the interval

Abstract: Hypermultiplets are considered in the five-dimensional interval where all fields are continuous and the boundary conditions are dynamically obtained from the action principle. The orbifold boundary conditions are obtained as particular cases. We can interpret the Scherk-Schwarz supersymmetry breaking as a misalignment of boundary conditions while a new source of supersymmetry breaking corresponding to a mismatch of different boundary parameters is identified. The latter can be viewed as coming from boundary supersymmetry breaking masses for hyperscalars and the nature of the corresponding supersymmetry breaking parameter is analyzed. For some regions of the parameter space where supersymmetry is broken (either by Scherk-Schwarz boundary conditions or by boundary hyperscalar masses) electroweak symmetry breaking can be triggered at the tree level.

Supersymmetry and Electroweak Breaking in the Interval

Abstract: Hypermultiplets are considered in the five-dimensional interval where all fields are continuous and the boundary conditions are dynamically obtained from the action principle. The orbifold boundary conditions are obtained as particular cases. We can interpret the Scherk-Schwarz supersymmetry breaking as a misalignment of boundary conditions while a new source of supersymmetry breaking corresponding to a mismatch of different boundary parameters is identified. The latter can be viewed as coming from boundary supersymmetry breaking masses for hyperscalars and the nature of the corresponding supersymmetry breaking parameter is analyzed. For some regions of the parameter space where supersymmetry is broken (either by Scherk-Schwarz boundary conditions or by boundary hyperscalar masses) electroweak symmetry breaking can be triggered at the tree level.

Some comments on the high energy emission from regions of star formation beyond the galaxy

Abstract: Regions that currently are or have been subject to a strong process of star formation are good candidates to be intense γ-ray and neutrino emitters. They may even perhaps be sites where ultra high energy cosmic rays are produced. Outside the Galaxy, the more powerful sites of star formation are found within very active galaxies such as starbursts (SGs) and Luminous or Ultra-Luminous Infrared Galaxies (LIRGs or ULIRGs). Some general characteristic of these objects are herein reviewed from the point of view of their possible status as high energy emitters. Revised estimations of the high energy gamma-ray yield of Arp 220 are presented.

Duality violations and spectral sum rules

Abstract: We study the issue of duality violations in the VV-AA vacuum polarization function in the chiral limit. This is done with the help of a model with an expansion in inverse powers of the number of colors, Nc, allowing us to consider resonances with a finite width. Due to these duality violations, the Operator Product Expansion (OPE) and the moments of the spectral function (e.g. the Weinberg sum rules) do not match at finite momentum, and we analyze this difference in detail. We also perform a comparative study of many of the different methods proposed in the literature for the extraction of the OPE parameters and find that, when applied to our model, they all fare quite similarly. In fact, the model strongly suggests that a significant improvement in precision can only be expected after duality violations are included. To this end, we propose a method to parameterize these duality violations. The method works quite well for the model, and we hope that it may also be useful in future determinations of OPE parameters in QCD.

The MAGIC Telescope and the observation of Gamma Ray Bursts

Abstract: The MAGIC Telescope, now taking data with an energy threshold well below 100 GeV, will soon be able to take full advantage of the fast slewing capability of its altazimuthal mount. Exploiting the link with the GCN network, the MAGIC Telescope could be one of the first ground-based experiments able to see the prompt emission of Gamma Ray Bursts in the few tens of GeV region.

Rational foundation of GR in terms of statistical mechanic in the AdS/CFT framework

Abstract: In this article, we work out the microscopic statistical foundation of the supergravity description of the simplest 1/2 BPS sector in the AdS(5)/CFT(4). Then, all the corresponding supergravity observables are related to thermodynamical observables, and General Relativity is understood as a mean-field theory. In particular, and as an example, the Superstar is studied and its thermodynamical properties clarified.

High energy gamma-ray emission from the starburst nucleus of NGC 253

Abstract: The high density medium that characterizes the central regions of starburst galaxies and its power to accelerate particles up to relativistic energies make these objects good candidates as $\gamma$-rays sources. In this paper, a self-consistent model of the multifrequency emission of the starburst galaxy NGC 253, from radio to gamma-rays, is presented. The model is in agreement with all current measurements and provides predictions for the high energy behavior of the NGC 253 central region. Prospects for observations with the HESS array and GLAST satellite are especially discussed.

Hadronic processes within collective stellar winds

Abstract: Recently, we have proposed that the interaction between relativistic protons resulting from Fermi first order acceleration in the superbubble of a stellar OB association or in other nearby accelerator and ions residing in single stellar winds of massive stars could lead to TeV sources without strong counterparts at lower energies. Here we refine this analysis in several directions. We study collective wind configurations produced by a number of massive stars, and obtain densities and expansion velocities of the stellar wind gas that is to be target of hadronic interactions. We study the expected $\gamma$-ray emission from these regions, considering in an approximate way the effect of cosmic ray modulation. We compute secondary particle production (electrons from knock-on interactions and electrons and positrons from charged pion decay), and solve the loss equation with ionization, synchrotron, bremsstrahlung, inverse Compton, and expansion losses. We provide examples where configurations can produce sources for GLAST satellite, and the MAGIC/HESS/VERITAS telescopes in non-uniform ways, i.e., with or without the corresponding counterparts. We show that in all cases we studied no EGRET source is expected. Finally, we comment on HESS J1303-631 and on Cygnus OB 2 and Westerlund 1 as two associations where this scenario could be tested.

Backsplash testbeam results for the SPD subdetector of LHCb

Abstract: The Scintillator Pad Detector (SPD) of the LHCb experiment [1] is positioned just before the preshower subdetector (PS), in front of the electromagnetic calorimeter (ECAL). It has been designed to complete the calorimeter information performing an e / γ identification for the experiment level-0 trigger system. Backscattered particles produced in the PS and the ECAL might introduce inefficiencies in the e / γ separation performed by the SPD. A testbeam with electrons and pions, at different energies, has allowed an experimental study of this effect.

Short study of the h-h 0 system in the two mixing angle scheme

Abstract: A two mixing angle description of the pseudoscalar decay constants associated to the h-h 0 system is used to parametrize the theoretical amplitudes of the radiative decays (h,h 0 ) ! gg and the coupling constants gV(h,h0)g with V = r,w,f. The parametrization is performed in both the “octet-singlet” basis and the “quark-flavour” basis. An excellent agreement with the most recent experimental data is achieved. Our analysis reveals that at the present experimental accuracy the two mixing angles differ significantly in the former basis but not in the latter, in accordance with the expectations of large Nc Chiral Perturbation Theory where the difference between the two mixing angles are due to a SU(3)f-breaking effect and a violation of the OZI rule respectively.

Meson Electroweak Interactions in Multicolor Quantum Chromodynamics

Abstract: This PhD Thesis is mainly devoted to the study of hadronic matrix elements of kaons. Its inner structure can be divided in three parts. In Chapter 3 we address the issue of quantum corrections in Resonance Chiral Lagrangians with the aid of the 1/N_c expansion. We compute, as an illustrative example, the coupling L_10 to one loop. Chapters 4 and 5 are the main body of the present work and deal with the determination of the relevant parameters in kaon phenomenology. We give a value for the invariant B_K, the kaon mass difference and \epsilon_K in a model-independent way, paying special attention to the issue of scale and scheme independence. In our approach, this is achieved in a very natural way once matching between long and short distances is ensured. We end up with a final chapter on the subject of duality violations in the VV-AA two-point correlator.

Phenomenological test of the large N_c ChPT predictions for the pseudoscalar mixing parameters

Abstract: A phenomenological analysis of various decay processes is performed in order to test the large $N_c$ Chiral Perturbation Theory predictions for the octet and singlet pseudoscalar decay constants and mixing angles. The results obtained hint at a disagreement with the expectations of this theoretical framework although the statistical significance is still limited.

Two mixing angle description of radiative VPgamma decays

Abstract: An analysis of various radiative $VP\gamma$ decays is performed using the two mixing angle description of the $\eta$-$\eta^\prime$ system. The agreement is excellent. Our results are expressed both in the ``octet-singlet'' and in the ``quark-flavour'' basis. It turns out that at the present experimental accuracy, the two angles are significantly different in the former, but not in the latter basis.

Impact of Duality Violations on Spectral Sum Rule Analyses

Abstract: Recent sum rule analyses on the two-point correlator have led to significant discrepancies in the values found for the OPE condensates, most dramatically in the dimension eight condensate and to a lesser extent in the dimension six one. Precise knowledge of these condensates is of relevance in kaon decays and therefore it seems mandatory to assess the actual impact of what is commonly neglected in spectral sum rules, most prominently the issue of duality violations. We will explicitly compute them in a toy model and show that they are a priori non-negligible.

Some comments on the high energy emission from regions of star formation beyond the galaxy

Abstract: Regions that currently are or have been subject to a strong process of star formation are good candidates to be intense gamma-ray and neutrino emitters. They may even perhaps be sites where ultra high energy cosmic rays are produced. Outside the Galaxy, the more powerful sites of star formation are found within very active galaxies such as starbursts (SGs) and Luminous or Ultra-Luminous Infrared Galaxies (LIRGs or ULIRGs). Some general characteristic of these objects are herein reviewed from the point of view of their possible status as high energy emitters. Revised estimations of the high energy gamma-ray yield of Arp 220 are presented.