Elementary Particles and Fields and String Theory Commons^™

Particle Physics Model For The 17 Mev Anomaly In Beryllium Nuclear Decays, Jonathan L. Feng, Bartosz Fornal, Iftah Galon, Susan Gardner, Jordan Smolinsky, Tim M. P. Tait, Philip Tanedo

Physics and Astronomy Faculty Publications

The 6.8σ anomaly in excited ⁸Be nuclear decays via internal pair creation is fit well by a new particle interpretation. In a previous analysis, we showed that a 17 MeV protophobic gauge boson provides a particle physics explanation of the anomaly consistent with all existing constraints. Here we begin with a review of the physics of internal pair creation in ⁸Be decays and the characteristics of the observed anomaly. To develop its particle interpretation, we provide an effective operator analysis for excited ⁸Be decays to particles with a variety of spins and parities and show that …

Locality And Efficient Evaluation Of Lattice Composite Fields: Overlap-Based Gauge Operators, Andrei Alexandru, Ivan Horváth

Physics and Astronomy Faculty Publications

We propose a novel general approach to locality of lattice composite fields, which in case of QCD involves locality in both quark and gauge degrees of freedom. The method is applied to gauge operators based on the overlap Dirac matrix elements, showing for the first time their local nature on realistic path-integral backgrounds. The framework entails a method for efficient evaluation of such nonultralocal operators, whose computational cost is volume independent at fixed accuracy, and only grows logarithmically as this accuracy approaches zero. This makes computation of useful operators, such as overlap-based topological density, practical. The key notion underlying these …

Neutron Decay Correlations In The Nab Experiment, L. J. Broussard, R. Alarcon, S. Baeßler, L. Barrón Palos, N. Birge, T. Bode, J. D. Bowman, T. Brunst, J. R. Calarco, J. Caylor, T. Chupp, V. Cianciolo, Christopher Crawford, G. W. Dodson, J. Dubois, W. Fan, W. Farrar, N. Fomin, E. Frlež, J. Fry, M. T. Gericke, F. Glück, G. L. Greene, R. K. Grzywacz, V. Gudkov, C. Hendrus, F. W. Hersman, T. Ito, H. Li, N. Macsai, Bradley R. Plaster, Aaron P. Sprow

Physics and Astronomy Faculty Publications

The Nab experiment will measure the correlation a between the momenta of the beta particle and antineutrino in neutron decay as well as the Fierz term b which distorts the beta spectrum.

Neutron-Antineutron Transitions: Exploring B – L Violation With Quarks, Xinshuai Yan

Theses and Dissertations--Physics and Astronomy

In the Standard Model (SM), the quantity baryon number (B) − lepton number (L), B − L, is perfectly conserved. Therefore, the observation of B − L violation would reveal the existence of physics beyond the SM. Traditionally, given the severe experimental constraints on |∆B| = 1 processes, B − L violation with baryons is probed via neutron-antineutron (n − n̄) oscillations, although this process suffers from quenching in the presence of external fields or matter.

In this dissertation, we discuss another possibility, n − n̄ conversion, in which the |∆ …

Disconnected-Sea Quarks Contribution To Nucleon Electromagnetic Form Factors, Raza Sabbir Sufian

Theses and Dissertations--Physics and Astronomy

We present comprehensive analysis of the light and strange disconnected-sea quarks contribution to the nucleon electric and magnetic form factors. The lattice QCD estimates of strange quark magnetic moment G^s_M (0) = −0.064(14)(09) μ_N and the mean squared charge radius ⟨r²_s⟩_E = −0.0043(16)(14) fm² are more precise than any existing experimental measurements and other lattice calculations. The lattice QCD calculation includes ensembles across several lattice volumes and lattice spacings with one of the ensembles at the physical pion mass. We have performed a simultaneous chiral, infinite volume, and continuum extrapolation in …

ΠN And Strangeness Sigma Terms At The Physical Point With Chiral Fermions, Yi-Bo Yang, Andrei Alexandru, Terrence Draper, Jian Liang, Keh-Fei Liu

Physics and Astronomy Faculty Publications

Lattice QCD calculations with chiral fermions of the πN sigma term σ_πN and strangeness sigma term σ_πN including chiral interpolation with continuum and volume corrections are provided in this work, with the excited-state contaminations subtracted properly. We calculate the scalar matrix element for the light/strange quark directly and find σ_πN = 45.9(7.4)(2.8)  MeV, with the disconnected insertion part contributing 20(12)(4)%, and σ_πN = 40.2(11.7)(3.5)  MeV, which is somewhat smaller than σ_πN. The ratio of the strange/light scalar matrix elements is y = 0.09(3)(1).

Measurements Of DN2 And AN1: Probing The Neutron Spin Structure, D. Flay, M. Posik, D. S. Parno, Kalyan C. Allada, W. R. Armstrong, T. Averett, F. Benmokhtar, W. Bertozzi, A. Camsonne, M. Canan, G. D. Cates, C. Chen, J. -P. Chen, S. Choi, E. Chudakov, F. Cusanno, M. M. Dalton, W. Deconinck, C. W. De Jager, X. Deng, A. Deur, Chiranjib Dutta, L. El Fassi, G. B. Franklin, M. Friend, H. Gao, F. Garibaldi, S. Gilad, R. Gilman, O. Glamazdin, Ameya Suresh Kolarkar, Wolfgang Korsch

Physics and Astronomy Faculty Publications

We report on the results of the E06-014 experiment performed at Jefferson Lab in Hall A, where a precision measurement of the twist-3 matrix element d₂ of the neutron (dⁿ₂) was conducted. The quantity dⁿ₂ represents the average color Lorentz force a struck quark experiences in a deep inelastic electron scattering event off a neutron due to its interaction with the hadronizing remnants. This color force was determined from a linear combination of the third moments of the ³He spin structure functions, g₁ and g₂, after nuclear corrections had …

Protophobic Fifth-Force Interpretation Of The Observed Anomaly In 8Be Nuclear Transitions, Jonathan L. Feng, Bartosz Fornal, Iftah Galon, Susan Gardner, Jordan Smolinsky, Tim M. P. Tait, Philip Tanedo

Physics and Astronomy Faculty Publications

Recently a 6.8σ anomaly has been reported in the opening angle and invariant mass distributions of e⁺e⁻ pairs produced in ⁸Be nuclear transitions. The data are explained by a 17 MeV vector gauge boson X that is produced in the decay of an excited state to the ground state, ⁸Be^∗ → ⁸Be X, and then decays through X → e⁺e⁻. The X boson mediates a fifth force with a characteristic range of 12 fm and has millicharged couplings to up and down quarks and electrons, and a …

New Prospects In Fixed Target Searches For Dark Forces With The Seaquest Experiment At Fermilab, Susan Gardner, R. J. Holt, A. S. Tadepalli

Physics and Astronomy Faculty Publications

An intense 120 GeV proton beam incident on an extremely long iron target generates enormous numbers of light-mass particles that also decay within that target. If one of these particles decays to a final state with a hidden gauge boson, or if such a particle is produced as a result of the initial collision, then that weakly interacting hidden-sector particle may traverse the remainder of the target and be detected downstream through its possible decay to an e⁺ e⁻, μ⁺ μ⁻, or π⁺ π⁻ final state. These conditions can be realized through …

Cpt, Cp, And C Transformations Of Fermions, And Their Consequences, In Theories With B − L Violation, Susan Gardner, Xinshuai Yan

Physics and Astronomy Faculty Publications

We consider the transformation properties of fermions under the discrete symmetries CPT, CP, and C in the presence of B − L violation. We thus generalize the analysis of the known properties of Majorana neutrinos, probed via neutrinoless double beta decay, to include the case of Dirac fermions with B − L violation, which can be probed via neutron-antineutron oscillations. We show that the resulting CPT phase has implications for the interplay of neutron-antineutron oscillations with external fields and sources and consider the differences in the Majorana dynamics of neutrinos and neutrons in the context of theories with …

An Apparatus For Studying Electrical Breakdown In Liquid Helium At 0.4 K And Testing Electrode Materials For The Neutron Electric Dipole Moment Experiment At The Spallation Neutron Source, T. M. Ito, J. C. Ramsey, W. Yao, D. H. Beck, V. Cianciolo, S. M. Clayton, Christopher B. Crawford, S. A. Currie, B. W. Filippone, W. C. Griffith, M. Makela, R. Schmid, G. M. Seidel, Z. Tang, D. Wagner, W. Wei, S. E. Williamson

Physics and Astronomy Faculty Publications

We have constructed an apparatus to study DC electrical breakdown in liquid helium at temperatures as low as 0.4 K and at pressures between the saturated vapor pressure and ∼600 Torr. The apparatus can house a set of electrodes that are 12 cm in diameter with a gap of 1–2 cm between them, and a potential up to ±50 kV can be applied to each electrode. Initial results demonstrated that it is possible to apply fields exceeding 100 kV/cm in a 1 cm gap between two electropolished stainless steel electrodes 12 cm in diameter for a wide range of pressures …

Narrow Nucleon-Ψ(2S) Bound State And Lhcb Pentaquarks, Michael I. Eides, Victor Yu. Petrov, Maxim V. Polyakov

Physics and Astronomy Faculty Publications

We interpret the newly discovered pentaquark P_c(4450) as a bound state of charmonium ψ(2S) and the nucleon. The binding potential is due to the charmonium-nucleon interaction that in the heavy quark approximation is proportional to the product of the charmonium chromoelectric polarizability and the nucleon energy-momentum distribution. We use the large Nc expansion to estimate the quarkonium polarizability and calculate the nucleon properties in the framework of the mean-field picture of light baryons. Two almost degenerate states J^P=(1/2)⁻ and J^P=(3/2)⁻ are predicted at the position of the P_{c …}

Orbital Angular Momentum And Generalized Transverse Momentum Distribution, Yong Zhao, Keh-Fei Liu, Yi-Bo Yang

Physics and Astronomy Faculty Publications

We show that, when boosted to the infinite momentum frame, the quark and gluon orbital angular momentum operators defined in the nucleon spin sum rule of Chen et al. are the same as those whose matrix elements correspond to the moments of generalized transverse momentum distributions. This completes the connection between the infinite momentum limit of each term in that sum rule and experimentally measurable observables. We also show that these orbital angular momentum operators can be defined locally and discuss the strategies of calculating them in lattice QCD.

Stochastic Model With Low Mode Substitution For Nucleon Isovector Matrix Elements, Yi-Bo Yang, Andrei Alexandru, Terrence Draper, Ming Gong, Keh-Fei Liu

Physics and Astronomy Faculty Publications

We introduce a stochastic method with low-mode substitution to evaluate the connected three-point functions. The isovector matrix elements of the nucleon for the axial-vector coupling g³_A, scalar couplings g³_S and the quark momentum fraction ⟨x⟩_u−d are calculated with overlap fermion on 2 + 1 flavor domain-wall configurations on a 24³ × 64 lattice at m_π = 330  MeV with lattice spacing a = 0.114  fm.

Lattice Qcd Calculation Of The Momentum Fraction Carried By Quarks In The Nucleon, And The Roper Puzzle, Mingyang Sun

Theses and Dissertations--Physics and Astronomy

This thesis is concerned with the lattice QCD calculation of the momentum fraction carried by quarks in the nucleon. Particularly, the strange quark contribution, (x)_s, is calculated, as well as the ratio of the strange (x) to that of u/d in the disconnected insertion which will be useful in constraining the global fit of parton distribution functions at small x. The disconnected insertion is known to be hard to calculate on the lattice. We adopt the overlap fermion action on several 2 + 1 flavor domain-wall fermion ensembles with a light sea quark mass which corresponds to pion …

Universal Constraints On 2d Cfts And 3d Gravity, Joshua D. Qualls

Theses and Dissertations--Physics and Astronomy

We study constraints imposed on a general unitary two-dimensional conformal field theory by modular invariance. We begin with a review of previous bounds on the conformal dimension Delta₁ of the lowest primary operator assuming unitarity, a discrete spectrum, modular invariance, c_L, c_R > 1, and no extended chiral algebra. We then obtain bounds on the conformal dimensions Delta₂, Delta₃ using no additional assumptions. We also show that in order to find a bound for Delta₄ or higher Delta_n, we need to assume a larger minimum value for c_tot that grows …

The Dijet Cross Section Measurement In Proton-Proton Collisions At A Center Of Mass Energy Of 500 Gev At Star, Grant D. Webb

Theses and Dissertations--Physics and Astronomy

Polarized deep inelastic scattering experiments play a vital role in the exploration of the spin structure of the proton. The polarized proton-proton collider at RHIC provides direct access to the gluon spin distribution through longitudinal double spin asymmetry measurements of inclusive jets, pions, and dijets. This thesis presents the measurement of the dijet double differential cross-section in proton-proton collisions at center of mass energies of √s = 500 GeV. The data represent an integrated luminosity of 8.7 pb^-1 recorded by the STAR detector during the 2009 RHIC run. A comprehensive jet analysis was performed to determine the ideal …

Time Dependent Holography, Diptarka Das

Theses and Dissertations--Physics and Astronomy

One of the most important results emerging from string theory is the gauge gravity duality (AdS/CFT correspondence) which tells us that certain problems in particular gravitational backgrounds can be exactly mapped to a particular dual gauge theory a quantum theory very similar to the one explaining the interactions between fundamental subatomic particles. The chief merit of the duality is that a difficult problem in one theory can be mapped to a simpler and solvable problem in the other theory. The duality can be used both ways.

Most of the current theoretical framework is suited to study equilibrium systems, or …

Investigation Of Spin-Independent Cp Violation In Neutron And Nuclear Radiative Β Decays, Daheng He

Theses and Dissertations--Physics and Astronomy

CP violation is an important condition to explain the preponderance of baryons in our universe, yet the available CP violation in the Standard Model (SM) via the so-called Cabibbo-Kobayashi-Maskawa mechanism seems to not provide enough CP violation. Thus searching for new sources of CP violation is one of the central tasks of modern physics. In this thesis, we focus on a new possible source of CP violation which generates triple-product correlations in momenta which can appear in neutron and nuclear radiative β decay. We show that at low energies such a CP violating correlation may arise from the exotic coupling …

Gauge-Gravity Duality And Its Applications To Cosmology And Fluid Dynamics, Jae-Hyuk Oh

University of Kentucky Doctoral Dissertations

This thesis is devoted to the study of two important applications of gauge-gravity duality: the cosmological singularity problem and conformal fluid dynamics. Gauge-gravity duality is a concrete dual relationship between a gauge theory (such as electromagnetism, the theories of weak and strong interactions), and a theory of strings which contains gravity. The most concrete application of this duality is the AdS/CFT correspondence, where the theory containing gravity lives in the bulk of an asymptotically anti-de-Sitter space-time, while the dual gauge theory is a deformation of a conformal field theory which lives on the boundary of anti-de-Sitter space-time(AdS).

Our first application …