Showing papers in "Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields in 2010"

micrOMEGAs: A Tool for dark matter studies

Abstract: micrOMEGAs is a tool for cold dark matter (DM) studies in generic extensions of the standard model with a R-parity like discrete symmetry that guarantees the stability of the lightest odd particle. The code computes the DM relic density, the elastic scattering cross sections of DM on nuclei relevant for direct detection, and the spectra of positrons, anti-protons and photons originating from DM annihilation including porpagation of charged cosmic rays. The cross sections and decay properties of new particles relevant for collider studies are included as well as constraints from the flavour sector on the parameter space of supersymmetric models.

The Indirect Search for Dark Matter from the centre of the Galaxy with the Fermi LAT

Abstract: Dark matter (DM) constitutes around a 25% of the Universe, while baryons only a 4%. DM can be reasonably assumed to be made of particles, and many theories (Super-symmetry, Universal Extra Dimensions, etc.) predict Weakly Interacting Massive Particles (WIMPs) as natural DM candidates at the weak scale. Self-annihilation (or decay) of WIMPs might produce secondary gamma-rays, via hadronization or as final state radiation. Since its launch in the 2008, the Large Area Telescope on-board of the Fermi gamma-ray Space Telescope has detected the largest amount of gamma-rays to date, in the 20MeV 300GeV energy range, allowing to perform a very sensitive indirect experimental search for DM (by means of high-energy gamma-rays). DM forms large gravitationally bounded structures, the halos, which can host entire galaxies, such as the Milky Way. The DM distribution in the central part of the halos is not experimentally know, despite a very large density enhancement might be present. As secondary gamma rays production is very sensitive to WIMP density, a very effective search can be performed from the regions where the largest density is expected. Therefore the information provided by the DM halo N-body simulations are crucial. The largest gamma-ray signal from DM annihilation is expected from the centre of the Galaxy. In the same region a large gamma-ray background is produced by bright discrete sources and the cosmic-rays interacting with the interstellar gas and the photons fields. Here we report an update of the indirect search for DM from the Galactic Center (GC).

Effective field theory for top quark physics

Abstract: Physics beyond the standard model can affect top-quark physics indirectly We describe the effective field theory approach to describing such physics, and contrast it with the vertex-function approach that has been pursued previously We argue that the effective field theory approach has many fundamental advantages and is also simpler

Charge asymmetry: a theory appraisal

Abstract: The most recent measurements at Tevatron of the charge asymmetry in top-antitop quark pair production reduce the discrepancy with the Standard Model from 2σ to 1.7σ, and open a little window, at 95% CL, for negative contributions to the charge asymmetry beyond the SM. We update our analysis for colour octet gauge bosons or axigluons in flavour universal and flavour non-universal scenarios. We review other possible models and make an educated guess on their parameter space allowed by the new measurements. Finally, we comment on the prospects to measure the charge asymmetry at the LHC.

Four-top production and t tbar + missing energy events at multi TeV e+e- colliders

Abstract: Four-top production and top pair production in association with missing energy at e+e− colliders are sensitive probes of beyond-the-Standard-Model physics. We consider Standard Model extensions containing a new U(1)' which couples preferably to the most massive states of the SMsuch as the top quark or Dark Matter but has suppressed couplings to all the light states of the SM, as inspired by Randall-Sundrum–like setups or theories of partial fermion compositeness. These simple models are poorly constrained by experimental data but lead to striking new signatures at colliders. In this paper we consider Z' �production in association with a top quark pair in 3TeV e+e− collisions at CLIC, leading to interesting four-top final states and tt + Emiss events.

Keynote: Some remarks on top

Abstract: A few key issues of present and future explorations of the physics of top quarks at the Tevatron and LHC are discussed.

Self-stimulated undulator radiation and its possible applications

Abstract: The phenomena of self-stimulation of incoherent undulator radiation (UR) emitted by particles in a system of undulators installed in the linear accelerators or quasi-isochronous storage rings are investigated. Possible applications of these phenomena for the beam physics and light sources are discussed.

Associated scalar-vector production at the LHC within an effective Lagrangian approach

Abstract: We consider the case in which a strong dynamics is responsible for Electro-Weak Symmetry Breaking (EWSB) and both a scalar h and a vector V , respectively a singlet and a triplet under a custodial SU(2), are relevant and have a mass below the cut-off Λ ≈ 4πv In this framework we study the total cross sections for the associated V h production at the LHC at 14TeV as functions of two independent free parameters

Super KEKB / Belle II Project

Abstract: We present the status of the KEKB accelerator and the Belle detector upgrade, along with several examples of physics measurements to be performed with Belle II at Super KEKB.

Unified First Law and Some Comments

Abstract: In this small article, unified first law has been analyzed and some results have been deduced from it. The results have been presented in the form of lemmas and some conclusions have been drawn from them. The joint venture of quantum mechanics and general relativity leads to a remarkable discovery that a ”black hole (BH) behaves like a black body”. The thermal radiation emitted by a BH has temperature proportional to its surface gravity at the horizon while entropy is proportional to the area of the horizon [1,2], i.e., T = � 2� , S = A 4G . Also this temperature entropy and the mass of the BH are related by the first law of thermodynamics [3]. Further, the equivalence of the thermodynamical quantities with the geometry of the horizon leads to speculate some inherent relationship between thermodynamical laws and Einstein equations. This speculation comes into true in 1995 when Jacobson [4] was able to formulate Einstein’s equations from the Clausius relation (�Q = TdS) using local Rindler Causal horizons with T, the Unruh temperature as seen by an accelerated observer just inside the horizon. The equivalence in other way round was shown by Padmanabhan [5] for a general spherical symmetric space time. However in other gravity theories, such type of equivalence is not possible. Eling et al [6] showed that the usual Clausius relation and the entropy assumption S = �f 0 (r)A(or S = �F (�)A) for f(R)gravity (or scalar tensor gravity) do not give the correct equations of motion-on entropy production term has to be added to the Clausius relation and as a result there will be non-equilibrium thermodynamics of space-time [6,7]. Similarly, in the context of BH thermodynamics most studies of BH thermodynamics are concentrated to stationary BHs. It is speculated that thermodynamics of dynamical (i.e., non stationary) BH is related to the non-equilibrium thermodynamics of the universe. Hayward [8] initiated the study of the thermodynamics of dynamical BH by proposing ”Unified first law”. He introduced the idea of the trapping horizon and was able to show the equivalence of Einstein equations and unified first law . He formulated the first law of thermodynamics for a dynamical BH by projecting unified first law along the trapping horizon. Also projecting along the tangent to the trapping horizon he was able to formulate the Clausius relation. Subsequently, Cai et al [7] studied in details the thermodynamics of FRW universe starting from the unified first law, in Einstein gravity, Lovelock gravity and in scalar-tensor theory of gravity and showed the necessity of introducing entropy production term in scalar tensor theory. In this small article we study the unified first law in details and reveal some of its properties in the form of lemmas. Mathematically, the unified first law can be written as

Recent Results on Flavor Physics from BaBar

Abstract: The authors report an update to their previous measurement of the CKM element |V{sub ub}| using exclusive B {yields} {pi}{ell}{nu} decays In the charm sector they have performed a measurement of f{sub D{sub s}} using D{sub s}{sup +} {yields} {tau}{sup +}{nu}{sub {tau}} decays, they have measured the mixing parameter y{sub CP} using the lifetime ratio / in D{sup 0} decays, and they have also searched for CP violation using T-odd correlations in D{sup 0} decays to K{sup +}K{sup -}{pi}{sup +}{pi}{sup -} Finally, in the tau sector they have performed a search for the lepton flavor violating decays {tau}{sup {+-}} {yields} e{sup {+-}}{gamma} and {tau}{sup {+-}} {yields} {mu}{sup {+-}}{gamma}

Rapidity Spectra of Heavy Baryons in Nuclear Collisions at Various Energies : A Systematic Approach

Abstract: ] produced in the nuclear collisions at some modestlyhigh energies. Furthermore, our objective is also to build up a comprehensive and consistentmethodology to analyze the data on this specific observable which has a very important placein the domain of High Energy Physics (HEP). On an overall basis, our target here attains amoderate degree of success even for production of such rare secondaries. In addition to this, thelimitations of such an approach have also been pointed out.Keywords: Relativistic heavy ion collisions; inclusive cross-section.PACS nos.:25.75.-q, 13.60.Hb

Measurements of vector boson plus jets at the Tevatron

Abstract: We present preliminary measurements of Z/{gamma}* + jets, W + c and Z + b + X at the Tevatron, and review recent measurements of vector boson plus inclusive and heavy-flavor jets production. All measurements are in agreement with next-to-leading-order QCD calculations within the experimental and theoretical uncertainties. We also point to comparisons of the production rate and kinematics of the data with several Monte Carlo simulation programs of vector boson + jets processes.

Collective flow and energy loss with parton transport

Abstract: Quenching of gluonic jets and heavy quark production in Au + Au collisions at RHIC can be understood within the pQCD-based (3+1)-dimensional parton transport model BAMPS including pQCD bremsstrahlung 2 ↔ 3 processes. Furthermore, the development of conical structures induced by gluonic jets is investigated in a static box for the regimes of small and large dissipation.

Single and double top quark production at the Tevatron

Abstract: Summary. — The CDF and D0 experiments have measured single and double top quark production in p¯ p collisions at the Tevatron at a centre-of-mass energy of 1.96TeV. The applied methods are used to constrain properties of the top quark and to search for new physics. Several methods of signal to background separation and of the estimation of the background contributions are discussed. Experimental results using an integraged luminosity up to 5.3fb −1 are presented.

A search for directional violations of the Lorentz invariance through the study of a possible asymmetry of particle lifetimes

Abstract: From the study of a sample of about 62.3 million well-reconstructed K0S → π+π− decays recorded by the KLOE detector at the DAΦNE accelerator in Frascati, the lifetimes of K0S mesons parallel and antiparallel to the direction of motion of the Earth with respect to the Cosmic Microwave Background (CMB) reference frame have been studied. No difference has been found, and a limit on a possible asymmetry of the lifetime with respect to the CMB has been set at 95% CL: |A|CMB = |τ+CMB − τ−CMB|/(τ+CMB + τ−CMB) < 0.98×10−3. This is presently the best experimental limit on such quantity, and it is smaller of the speed, expressed in natural units, of the Solar System with respect to the CMB (V/c = 1.23×10−3). The present limit might constrain possible Lorentz-violating anisotropical theories.

W+jets as a background to top physics: The Quest for many jets

Abstract: The latest progress in calculating electroweak gauge boson production in association with QCD jets at hadron colliders is summarized. Particular emphasis is given to the recently completed QCD one-loop calculations of W+3jets and Wb final states. Furthermore recent developments in improving Monte Carlo event generators by means of combining tree-level matrix elements with parton showers are reviewed.

Heavy Flavor Spectroscopy at the Tevatron

Abstract: The Tevatron experiments have each accumulated about 6 fb{sup -1} of good data since the start of Run II. This large dataset provides excellent opportunities for heavy flavor spectroscopy studies at the Tevatron. This article will cover the latest {Upsilon}(nS) polarization studies as well as exotic meson spectroscopy results.

Physics Beyond the Single Top Quark Observation

Abstract: In March 2009, the DO Collaboration first observed the electroweak production of single top quarks at 5σ significance. We measured the cross section for the combined s-channel and t-channel production modes, and set a lower limit on the CKM matrix element |Vtb|. Since then, we have used the same dataset to measure the t-channel production mode independently, the combined cross section in the hadronically decaying tau lepton final state, and the width and lifetime of the top quark, and we have set upper limits on contributions from anomalous flavor-changing neutral currents. This paper describes these new measurements, as presented at the 3rd International Workshop on Top Quark Physics, held in Bruges, Belgium, May 31–June 4, 2010.

K rare decays with NA62

Abstract: The long-term goal of NA62 is to measure the ultra rare K ± → π ± ν¯ν decay with a sensitivity of 10−12 per event. This is done by using the decay-in-flight technique which allows a signal acceptance of ∼ 10%. The aim is to collect about 100 signal events in two years of data taking with a background-to-signal ratio smaller than 10%. The principle of the experimental measurement and the layout of the detector are presented. During 2007/2008 a dedicated run devoted to NA62 prototype tests and study of Ke2 decays was taken. The first phase of the NA62 experiment is aiming at a high-precision test of the lepton universality by measuring the helicity suppressed ratio RK. The preliminary result based on 40% of the 2007 NA62 data sample, RK = Ke2/Kμ2 = (2.500 ± 0.016) × 10−5, which is the first result with a precision better than 1%, is consistent with the Standard Model. Aiming at charge asymmetry measurements, the NA48/2 experiment collected an unprecedented amount of charged K3π events. The large samples allowed a precision measurement of rare charged kaon decays. New measurements of the K ± π�� decays based on the full NA48/2 data sample collected during 2003/2004 are reported in this paper. Samples of about 7200 reconstructed K ± → π ± e+e− events, and more than 3000 K ± → π ± μ+μ− events, with a few percent background contamination, have been collected. A precise measurement of the branching fractions and the form factors of the rare decays K ± π�� were performed. Measurements of the CP-violating and the forward-backward asymmetries are reported.

Flaring Active Galactic Nuclei. The cases of 3C 279 and PMN J0948+0022 as seen by the Fermi-LAT

Abstract: Active galactic nuclei (AGNs) exhibit variability across the entire electromagnetic spectrum with distinct flaring episodes at different frequencies. The high sensitivity and nearly uniform sky coverage of the Large Area Telescope on board the Fermi satellite make it a powerful tool for monitoring a large number of AGNs over long timescales. This allowed us to detect several flaring AGNs in gamma rays, triggering dedicated multifrequency campaigns on these sources from radio to TeV energies. We discuss the results for two different types of flaring AGN: the flat spectrum radio quasar 3C 279, in particular the coincidence of a gamma-ray flare from this source with the drastic change of the optical polarization angle, and the first gamma-ray flare from a radio-loud narrow-line Seyfert 1, PMN J0948+0022.

To be or not to be: Higgs impostors at the LHC

Abstract: Consider the day when an invariant mass peak, roughly compatible with “the Higgs”, begins to emerge, say at the LHC, . . . and may you see that day. There will be a difference between discovery and scrutiny. The latter would involve an effort to ascertain what it is, or is not, that has been found. It turns out that the two concepts are linked: Scrutiny will naturally result in deeper knowledge—is *this* what you were all looking for?—but may also speed up discovery.

Turning on the LHC: Commissioning with beam and the outlook for 2010

Abstract: After the September 19th 2008 incident and an intense year of recovery, consolidation and testing, LHC beam commissioning started again on the 23rd November 2009 and continued for three and a half weeks before the annual Christmas stop. A summary of the progress made and the performance of the individual accelerator systems is given. The potential performance of 2010 is discussed.

Flavor physics within and beyond the Standard Model

Abstract: I review recent progress in theoretical calculations related to the CKM unitarity triangle After briefly discussing hints for new physics in Bd-Bd and Bs-Bs mixing I present three topics of MSSM flavour physics: First I discuss new tan β-enhanced radiative corrections to flavour-changing neutral current (FCNC) amplitudes which go beyond the familiar Higgs-mediated FCNC diagrams and may enhance the mixing-induced CP asymmetry in Bd → φKS The second topic is a reappraisal of the idea that flavour violation originates from the soft supersymmetry-breaking terms Finally I discuss how μ → eγ can be used to constrain the flavour structure of the dimension-5 Yukawa interactions which appear in realistic grand-unified theories