120618992
Eigenvalue Distribution of Large $N$ Random Matrix--- A Direct Diagrammatic Proof to Marchenko-Pastur Law ---
In various theoretical models, large N limit has been a very useful tool, both at a qualitative and a quantitative level [1]. It works as a great approximation, even when the actual dimension of the matrix is not a very large number, such as Nc = 3 in QCD [2, 3] and Nf = 3 in neutrino anarchy [4]. It is thus useful to understand the behavior of large N random matrices as much as possible. In random matrix theory, there is a powerful law— Marchenko-Pastur (MP) law [5]—that governs the asymptotic eigenvalue distribution of large-dimension random matrices. In this paper we provide an alternative proof to it. We first state Marchenko Pastur law in Section II. Then in Section III, we present a detailed proof of MP law using Feynman diagrams. We extend our proof to symmetric matrix case in Section IV. Section V is our conclusion.
118605527
How to use the Standard Model effective field theory
A bstractWe present a practical three-step procedure of using the Standard Model effective field theory (SM EFT) to connect ultraviolet (UV) models of new physics with weak scale precision observables. With this procedure, one can interpret precision measurements as constraints on a given UV model. We give a detailed explanation for calculating the effective action up to one-loop order in a manifestly gauge covariant fashion. This covariant derivative expansion method dramatically simplifies the process of matching a UV model with the SM EFT, and also makes available a universal formalism that is easy to use for a variety of UV models. A few general aspects of RG running effects and choosing operator bases are discussed. Finally, we provide mapping results between the bosonic sector of the SM EFT and a complete set of precision electroweak and Higgs observables to which present and near future experiments are sensitive. Many results and tools which should prove useful to those wishing to use the SM EFT are detailed in several appendices.
116450098
What do precision Higgs measurements buy us
We study the sensitivities of future precision Higgs measurements and electroweak observables in probing physics beyond the Standard Model. Using effective field theory--appropriate since precision measurements are indirect probes of new physics--we examine two well-motivated test cases. One is a tree-level example due to a singlet scalar field that enables the first-order electroweak phase transition for baryogenesis. The other is a one-loop example due to scalar top in the MSSM. We find both Higgs and electroweak measurements are sensitive probes of these cases.
20926318
Natural Higgs mass in supersymmetry from nondecoupling effects.
The Higgs mass implies fine-tuning for minimal theories of weak-scale supersymmetry (SUSY). Nondecoupling effects can boost the Higgs mass when new states interact with the Higgs boson, but new sources of SUSY breaking that accompany such extensions threaten naturalness. We show that two singlets with a Dirac mass can increase the Higgs mass while maintaining naturalness in the presence of large SUSY breaking in the singlet sector. We explore the modified Higgs phenomenology of this scenario, which we call the "Dirac next-to-minimal supersymmetric standard model."
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.
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.
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.
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.
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.