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At least 325 records · Page 18

Symmetry tests in photo-pion production

Small angle electron scattering with intense electron beams opens up the possibility of performing almost real photon induced reactions with thin, polarized hydrogen and few body targets, allowing for the detection of low energy charged particles. This promises to be much more effective than conventional photon tagging techniques. For photo-pion reactions some fundamental new possibilities include: tests of charge symmetry in the N-N system by measurement of the neutron-neutron scattering length a{sub nn} in the and ggrD → π{sup +}nn reaction; tests of isospin breaking due to the mass difference of the up and down quarks; measurements with polarized targets are sensitive to πN phase shifts and will test the validity of the Fermi-Watson (final state interaction) theorem. All of these experiments will test the accuracy and energy region of validity of chiral effective theories.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Lattice QCD for nuclear physics

A brief overview of the current and expected contributions of lattice QCD to various aspects of low-energy nuclear physics is presented. Recent investigations of light nuclei, hyperon-nucleon and nucleon-nucleon interactions are discussed and a first investigation of multi-hadron structure is highlighted.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Physics with charmonium - Highlights of BESIII and PANDA

The physics of the strong interaction is undoubtedly one of the most challenging areas of modern science. Quantum ChromoDynamics (QCD) is reproducing successfully the physics phenomena at distances much shorter than the size of the nucleon, where perturbation theory can be used yielding results of high precision and predictive power. At larger distance scales, however, perturbative methods cannot be applied anymore, although spectacular phenomena, such as the generation of hadron masses and quark confinement, occur. Studies using charmed quarks and gluon-rich matter have the potential to connect the perturbative and the non-perturbative QCD region. The annihilation of matter with antimatter in the mass regime of charmonium is an ideal environment to discover new states or transitions that could reveal the secrets of the strong interaction. Hadronic and electromagnetic transitions between charmonium states and their decays have been measured with a world-record in precision with the BESIII spectrometer at the electron-positron collider at IHEP Beijing, China. Moreover, unconventional narrow charmonium-rich states have been discovered recently in an energy regime above the open-charm threshold, thereby, possibly initiating a new era in charmonium spectroscopy. The near future experiment, PANDA, at the research facility FAIR in Germany, Darmstadt, will exploit the annihilation of cooled anti-protons with protons to perform charmonium spectroscopy with an incredible precision. I will present the most promising results that have been recently obtained with BESIII together with the future perspectives of PANDA in the field of charmonium spectroscopy.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

The Tsallis distribution at the LHC: Phenomenology

An overview is presented of transverse momentum distributions of particles at the LHC using the Tsallis distribution. The use of a thermodynamically consistent form of this distribution leads to an excellent description of charged and identified particles. The values of the Tsallis parameter q are truly remarkably consistent.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

First detection of high-energy astrophysical neutrinos with IceCube

The IceCube detector at the South Pole is the world’s largest neutrino telescope, instrumenting a cubic kilometre of deep clear ice. Completed in late 2010, the detector has recorded the arrival directions and energies of tens of thousands of neutrinos – mostly those produced when cosmic rays collide with the Earth’s atmosphere. Here, we report on the first observation of high-energy neutrinos from beyond the Earth’s atmosphere, identified using a novel method to strongly suppress atmospheric neutrinos coming downward into the detector from the southern sky, leaving a sample of neutrinos highly likely to be of astrophysical origin.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Neutrino mass hierarchy: Theory and phenomenology

I discuss the motivation for the neutrino mass hierarchy determination, the methods to access the mass hierarchy, and technological approaches using these methods.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Future long-baseline neutrino oscillations: View from Asia

Accelerator based long-baseline neutrino oscillation experiments have been playing important roles in revealing the nature of neutrinos. However, it turned out that the current experiments are not sufficient to study two major remaining problems, the CP violation in the lepton sector and the mass hierarchy of neutrinos. Therefore, several new experiments have been proposed. Among of them, two accelerator based long-baseline neutrino oscillation experiments, the J-PARC neutrino beam and Hyper-Kamiokande, and MOMENT, have been proposed in Asia. These two projects are reviewed in this article.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Future short-baseline sterile neutrino searches with accelerators

A number of experimental anomalies in neutrino oscillation physics point to the existence of at least one light sterile neutrino. This hypothesis can be precisely tested using neutrinos from reactors, radioactive isotopes, and particle accelerators. The focus of these proceedings is on future dedicated short-baseline sterile neutrino searches using accelerators.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Measurement of exclusive dijet production in diffractive DIS with the ZEUS detector at HERA

The exclusive production of dijets in diffractive deep inelastic lepton–proton scattering has been measured with the ZEUS detector at HERA with an integrated luminosity of 372 pb{sup −1}. Jets have been reconstructed in the photon–Pomeron rest frame using the exclusive k{sub T} algorithm. The shape of the differential cross-section as a function of the angle between the plane spanned by the incoming and scattered lepton momenta and the plane spanned by the virtual photon and jets momenta is presented. The shape is determined by the jet production mechanism and provides information about the Pomeron structure.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Access to generalized parton distributions at COMPASS

A brief experimentalist's introduction to Generalized Parton Distributions (GPDs) is given. Recent COMPASS results are shown on transverse target-spin asymmetries in hard exclusive ρ{sup 0} production and their interpretation in terms of a phenomenological model as indication for chiral-odd, transverse GPDs is discussed. For deeply virtual Compton scattering, it is briefly outlined how to access GPDs and projections are shown for future COMPASS measurements.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

Diffraction and forward physics results of the ATLAS experiment from the Run I

Various aspects of forward physics have been studied by the ATLAS collaboration using data from Run I at the LHC. In this text, main results of four published analyses are summarized, all based on data from proton-proton collisions at √(s)=7 TeV collected in 2010 or 2011. Two analyses deal with the diffractive signature, one based on single-sided events, the other on large rapidity gaps in soft events. In addition, a recent measurement of the total pp cross section using the ALFA subdetector and a recent study of higher-order QCD effects using a jet veto are discussed.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

CMS results on multijet correlations

We present recent CMS measurements on multijet correlations using forward and low-p{sub T} jets, focusing on searches for BFKL and saturation phenomena. In pp collisions at √(s)=7 TeV, azimuthal correlations in dijets separated in rapidity by up to 9.4 units were measured. The results are compared to BFKL- and DGLAP-based predictions. In pp collisions at √(s)=8 TeV, cross sections for jets with p{sub T} > 21 GeV and |y| < 4.7, and for track-jets with p{sub T} > 1 GeV (minijets) are presented. The minijet results are sensitive to the bound imposed by the total inelastic cross section, and are compared to various models for taming the growth of the 2 → 2 cross section at low p{sub T}.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

STAR results on central exclusive production in proton-proton collisions

We present a preliminary measurement of the Central Exclusive Production of the two oppositely charged pions produced in the process pp → ppπ{sup +} π{sup −}, obtained with the STAR detector at RHIC at √(s)=200 GeV. Silicon strip detectors placed in Roman Pots were used for tagging forward protons while pion pair tracks were reconstructed in the STAR Time Projection Chamber. Predictions of models based on Regge phenomenology are compared to the spectra of the kinematical variables corrected for detector acceptance and efficiency.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

Central exclusive π{sup +}π{sup −} production in pp{sup ¯} collisions at √(s)=0.9 and 1.96 TeV at CDF

Exclusive π{sup +}π{sup −} production in proton-antiproton collisions at √(s)=0.9 and 1.96 TeV in the Collider Detector at Fermilab has been measured. Events with exactly two particles with opposite charge, in |η(π)| < 1.3, with no other particles detected in |η(π)| < 5.9, were selected. We require the central π{sup +}π{sup −} state to have rapidity |y(ππ)| < 1. The data are expected to be dominated by double pomeron exchange. Therefore, the quantum numbers of the central state are constrained. The data show resonance structures attributed to the f{sub 0} and f{sub 2} mesons. The results are valuable for light hadron spectroscopy, and for understanding the nature of the pomeron in a region between non-perturbative and perturbative QCD.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

The spin physics results from COMPASS

COMPASS (COmmon Muon and Proton Apparatus for Structure and Spectroscopy) is a fixed target experiment at CERN dedicated to studies of the spin structure of the nucleon and of the spectroscopy of hadrons. During the years 2002-2004, 2006-2007 and 2010-2011 the COMPASS collaboration has collected a large amount of data by scattering polarized 160(200) GeV/c muons on polarized {sup 6}LiD and NH{sub 3} targets. The COMPASS results on quark and gluon helicities are discussed, as well as results on transverse spin and transverse momentum effects in semi-inclusive deeply inelastic scattering.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Double parton effects for jets with large rapidity separation

We discuss production of four jets pp → jjjjX with at least two jets with large rapidity separation in proton-proton collisions at the LHC through the mechanism of double-parton scattering (DPS). The cross section is calculated in a factorizaed approximation. Each hard subprocess is calculated in LO collinear approximation. The LO pQCD calculations are shown to give a reasonably good descritption of CMS and ATLAS data on inclusive jet production. It is shown that relative contribution of DPS is growing with increasing rapidity distance between the most remote jets, center-of-mass energy and with decreasing (mini)jet transverse momenta. We show also result for angular azimuthal dijet correlations calculated in the framework of k{sub t} -factorization approximation.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗