118391627
Measurement of hadron composition in charged jets from pp collisions with the ALICE experiment
Abstract We report the first measurement of charged pion, kaon and (anti-)proton production in jets from hadron colliders. The measurement was carried out with the ALICE detector using 2 × 10 8 minimum bias pp collisions at a centre-of-mass energy of s = 7 TeV at the LHC. We present the π, K and p transverse momentum ( p T ) spectra, as well as the spectra of the reduced momentum ( z ch ≡ p T track / p T,jet ch ), in charged jets of p T between 5–20 GeV/c. The measurement is compared to Monte Carlo calculations.
119116044
Energy loss signals in the ALICETRD
Abstract We present the energy loss measurements with the ALICE TRD in the β γ range 1–10 4 , where β = v / c and γ = 1 / 1 − β 2 . The measurements are conducted in three different scenarios: (1)with pions and electrons from testbeams; (2)with protons, pions and electrons in proton–proton collisions at center-of-mass energy 7 TeV; (3)with muons detected in ALICE cosmic runs. In the testbeam and cosmic ray measurements, ionization energy loss (d E /d x ) signal as well as ionization energy loss plus transition radiation (d E /d x +TR) signal are measured. With cosmic muons the onset of TR is observed. Signals from TeV cosmic muons are consistent with those from GeV electrons in the other measurements. Numerical descriptions of the signal spectra and the β γ - dependence of the most probable signals are also presented.
119681467
Exploring the performance limits of the ALICE Time Projection Chamber and Transition Radiation Detector for measuring identified hadron production at the LHC
The Time Projection Chamber (TPC) and Transition Radiation Detector (TRD) are the 
main tracking and particle identification devices in the ALICE experiment at the CERN 
LHC. This thesis studies aspects of their performance beyond the original designs. This 
includes extending the TPC momentum measurement for cosmic rays to sub-TeV scale, 
investigating a robust identification method for electrons and hadrons by the TRD, and 
developing new approaches to characterize the TPC and TRD signals. These studies lead 
to an intriguing observation of the transition radiation from sub-TeV cosmic muons, and 
a universal method -- the TPC coherent fit -- to extract yields of different particle species 
with momentum from 0.5 to above 20 GeV/c. 
 
With the TPC coherent fit, transverse momentum spectra (0.6 < pt < 20 GeV/c) of pions, 
kaons and protons at mid-rapidity (|y|<~0.8) in pp collisions at sqrt(s) = 2.76 and 7 TeV and 
Pb-Pb collisions at sqrt(s_NN) = 2.76 TeV at the LHC are measured. In this unified approach 
both the anomalous enhancement of the proton-to-pion ratio at moderate pt (2-8 GeV/c) 
(the so-called baryon anomaly) and the nuclear modification of particle yields up to 
high pt (> 10 GeV/c) in Pb-Pb collisions are observed. The particle production is also 
studied in jets from pp collisions at 7 TeV and the results are well described by Perugia-0 
tune of PYTHIA6.
195751286
The HERMES Recoil Detector : Particle Identification and Determination of Detector Efficiency of the Scintillating Fiber Tracker
HERMES is a fixed target experiment using the HERA 27.6 GeV polarized electron/positron beams. With the polarized beams and its gas targets, which can be highly polarized, HERMES is dedicated to study the nucleon spin structure. One of its current physics programs is to measure deeply virtual Compton scattering (DVCS). In order to detect the recoiling proton the Recoil Detector was installed in the target region in the winter of 2005, taking data until the HERA-shutdown in the summer of 2007. The Recoil Detector measured energy loss of the traversing particles with its sub-detectors, including the silicon strip detector and the scintillating fiber tracker. This enables particle identification for protons and pions. In this work a systematic particle identification procedure is developed, whose performance is quantified. Another aspect of this work is the determination of the detector efficiency of the scintillating fiber tracker. Kurzfassung HERMES ist ein Fixed-Target-Experiment zur Untersuchung des Nukleonenspins. Der 27.6 GeV polarisierter Elektron-/Positron-Strahl von HERA wurde auf das hoch polarisierbare Gastarget geleitet. Eines der aktuellen Physikprogramme bei HERMES ist die Messung der tief virtuellen Compton-Streuung (DVCS). Um das rückgestreute Proton nachzuweisen wurde im Winter 2005 der Recoil-Detektor um das Target installiert, der bis zum HERA-Shutdown im Sommer 2007 Daten genommen hat. Der Recoil-Detektor maß den Energieverlust der durchgehenden Teilchen mittels eines Silizium-Streifen-Detektors und eines Trackers aus szintillierenden Fasern. Er ermöglicht so eine Teilchenidentifizierung für Protonen und Pionen. In dieser Arbeit wurde ein systematisches Teilchenidentifizierungsverfahren entwickelt, dessen Leistung quantitativ beschrieben wird. Ein anderer Aspekt dieser Arbeit ist die Bestimmung der Detektoreffizienz des Szintillierenden-Fasern-Trackers.
119391728
Quantum Version of Gauge Invariance and Nucleon Internal Structure
The conflict between cononical commutation relation and gauge invariance, which both the momentum and angular momentum of quark and gluon should satisfy, is clarified. The quantum version of gauge invariance is studied. The gauge independence of the matrix elements of quark momentum and angular momentum operators between physical states are proved. We suggest to use the canonical quark momentum and angular momentum distributions to describe the nucleon internal structure in order to establish an internal consistent description of hadron spectroscopy and hadron structure. The same problem for the atomic spectroscopy and structure is discussed.
118627065
Spin and orbital angular momentum in gauge theories (II): QCD and nucleon spin structure
Parallel to the construction of gauge invariant spin and orbital angular momentum for QED in paper (I) of this series, we present here an analogous but non-trivial solution for QCD. Explicitly gauge invariant spin and orbital angular momentum operators of quarks and gluons are obtained. This was previously thought to be an impossible task, and opens a more promising avenue towards the understanding of the nucleon spin structure.
53654264
Neutrino mass anarchy and the Universe
A bstractWe study the consequence of the neutrino mass anarchy on cosmology, in particular the total mass of neutrinos and baryon asymmetry through leptogenesis. We require independence of measure in each mass matrix elements in addition to the basis independence, which uniquely picks the Gaussian measure. A simple approximate U(1) flavor symmetry makes leptogenesis highly successful. Correlations between the baryon asymmetry and the light-neutrino quantities are investigated. We also discuss possible implications of recently suggested large total mass of neutrinos by the SDSS/BOSS data.
118243317
Spin and orbital angular momentum in gauge theories. I. QED and determination of the angular momentum density
This two-paper series addresses and fixes the long-standing gauge invariance problem of angular momentum in gauge theories. This QED part reveals: 1) The spin and orbital angular momenta of electrons and photons can all be consistently defined gauge invariantly. 2) These gauge-invariant quantities can be conveniently computed via the canonical, gauge-dependent operators (e.g, $\psi ^\dagger \vec x \times\frac 1i \vec \nabla \psi$) in the Coulomb gauge, which is in fact what people (unconsciously) do in atomic physics. 3) The renowned formula $\vec x\times(\vec E\times\vec B)$ is a wrong density for the electromagnetic angular momentum. The angular distribution of angular-momentum flow in polarized atomic radiation is properly described not by this formula, but by the gauge invariant quantities defined here. The QCD paper [arXiv:0907.1284] will give a non-trivial generalization to non-Abelian gauge theories, and discuss the connection to nucleon spin structure.
119456083
Effective Photon Mass in Nuclear Matter and Finite Nuclei
Electromagnetic field in nuclear matter and nuclei are studied. In the nuclear matter, because the expectation value of the electric charge density operator is not zero, different in vacuum, the U(l) local gauge symmetry of electric charge is spontaneously broken, and consequently, the photon gains an effective mass through the Higgs mechanism. An alternative way to study the effective mass of photon is to calculate the self-energy of photon perturbatively. It shows that the effective mass of photon is about 5.42 MeV in the symmetric nuclear matter at the saturation density rho(0) = 0.16 fm(-3) and about 2.0 MeV at the surface of U-238. It Seems that the two-body decay of a massive photon causes the sharp lines of electron-positron pairs in the low energy heavy ion collision experiments of U-238 + Th-232.