Tanmoy Bhattacharya

Alexander Friedland

Michael L. Graesser

Rajan Gupta

Emil Mottola

Michael S. Warren

#### Los Alamos HEP Theory Quarterly Report 2014-01

Tanmoy Bhattacharya, Alexander Friedland, Michael L. Graesser, Rajan Gupta, Emil Mottola, Michael S. Warren

The theory group is active in a number of diverse areas of research. Their primary areas of interest are in physics beyond the Standard Model, cosmology, dark matter, lattice quantum chromodynamics, neutrinos, the fundamentals of quantum field theory and gravity, and particle astrophysics. Generally the questions pursued by this group relate to deep mysteries in our understanding of Nature at the boundaries of the Standard Model and the grammar we use to describe it–quantum field theory and General Relativity. The theory group continues to make advances at the forefront of research in these areas.

#### Lattice QCD

The Los Alamos Lattice QCD team and their collaborators are carrying out four precision studies investigating signatures of new physics at the TeV scale, elucidating the structure of the nucleon, and understanding QCD at finite temperature. Progress on these four projects is described below.

#### Nucleon charges and form-factors

Bhattacharya, Gupta, Yoon and their external collaborators (the PNDME collaboration) has reanalyzed the calculation of renormalization constants and the effect of smearing the lattices to reduce short distance noise. Based on better understanding, they are revising the manuscript (arXiv:1306.5435) in which they probe novel scalar and tensor interactions at the TeV scale by calculating matrix elements of scalar and tensor quark bilinears within a nucleon state. They have also developed the codes to do these calculations on cluster and GPU computers at Los Alamos and have started the analysis of the largest 643×144 lattices at the weakest coupling there.

#### Matrix elements of novel CP violating operators and nEDM

Bhattacharya, Cirigliano and Gupta are carrying out the analysis of the mixing and renormalization of novel CP violating operators that contribute to the Neutron Electric Dipole Moment. They have determined an operator basis that allows for off-shell renormalization using external fixed momentum states, and a paper describing the one-loop matching between MSbar and a renormalization independent scheme is in progress. The numerical calculations have been started in collaboration with the RBC group using resources provided by the national USQCD initiative.

#### Behavior of QCD at finite temperature

Bhattacharya and Gupta are continuing the statistical analysis of the entire data set generated by the full HotQCD collaboration to determine the equation of state. The final data analysis is expected to be completed by March 2014. They have also contributed to the analysis and writing of the manuscript on the deconfinement transition and U(1) axial anomaly using Domain Wall fermions being prepared for publication in PRL using domain wall fermions.

#### Disconnected diagrams and Transverse Momentum Distribution Functions

Bhattacharya, Gupta and Yoon, in collaboration with Michael Engelhardt, have started testing the computer programs to investigate signal in both connected and disconnected diagrams that will be needed to evaluate the Sivers function and other transverse momentum distribution functions. These calculations are being done on computing resources at JLab.

#### Improving searches for new particles at the LHC

Graesser and LANL post-doc Jinrui Huang continue to investigate whether a top squark lighter than the top quark is allowed by all data. In this scenario the light top squarks decay through three-body and possibly four-body decay channels. That is, top squarks decaying into b quark, on-shell W and neutralino and/or decaying into b quark, stau and neutralino final states are being investigated. In addition to constraining this scenario using data from direct searches for top squark and chargino/neutralino/stau pair production, Graesser and Huang are investigating constraints arising from the top quark pair production cross-sections measured at both the LHC and the Tevatron. Preliminary results indicate the good agreement between the theoretical prediction for the top pair production—now known to NNLO—and experimental measurements provides an important constraint on the bW-neutralino final state, though less so on the stau final states.

#### Precision Cosmology Simulations

At the Supercomputing '13 conference, Warren reported on improvements made over the past two decades to his adaptive treecode N-body method (HOT). A mathematical and computational approach to the cosmological N-body problem was described, with performance and scalability measured up to 256k (218) processors. We presented error analysis and scientific application results from a series of more than ten 69 billion particle cosmological simulations. These results include the first simulations using the new constraints on the standard model of cosmology from the Planck satellite.

Reference: M. S. Warren, 2HOT: An Improved Parallel Hashed Oct-tree N-body Algorithm for Cosmological Simulation, Proceedings of SC13: International Conference for High Performance Computing, Networking, Storage and Analysis,2013 (Best paper finalist).

#### Quantum Field Theory and Gravity

Mercator Fellowship at the Univ. of Jena, Germany

From Oct. to Dec., 2013 Mottola was a visiting Mercator Fellow supported by the DFG (German Science Foundation) at the Friedrich Schiller Universität in Jena, Germany. He gave several lectures to Ph. D. students there and co-organizer a workshop on Strongly Interacting Field Theories” at Jena, Nov. 14–16, 2013. Several new collaborations were begun with Prof. A. Wipf, M. Ansorg, H. Gies,and F. Karbstein in both the Theoretical Physics and Relativity groups at Jena.

Partly as a result of these collaborations, Mottola has been nominated for a Humboldt Fellowship in Germany.

While in Europe, Mottola also visited Profs. G. Dvali and V. Mukhanov at the Ludwig Maximillian Univ., Munich, Germany, Profs. J. Berges and J. Pawlowski at the Univ. of Heidelberg, and Prof. I. Antoniadis at CERN. In addition collaborations were continued by meeting with Prof. C. Corianò of the Univ. of Salento, Italy at both Jena and CERN.

The following invited seminars were given during this three month period:

The Instability of de Sitter Space and the Schwinger Effect,” Theoretisch-Physikalisches Institut, Friedrich Schiller Univ., Jena, Germany, Nov. 6, 2013.
Scalar Boson Condensates and Macroscopic Effects of the Quantum Conformal Anomaly,” Workshop on Strongly-Interacting Field Theories, Friedrich Schiller Univ., Jena, Germany, Nov. 14–16, 2013.
Scalar Condensates and Macroscopic Effects of the Quantum Conformal Anomaly,” A. Sommerfeld Ctr. for Theoretical Physics seminar, Ludwig Maximilian Univ., Munich, Germany, Nov. 25, 2013.
Instability of de Sitter Space, the Schwinger Effect and Dynamical Dark Energy,” CERN, TH seminar, Geneva, Switzerland, Dec. 2, 2013.
What's the (Quantum) Matter with Black Holes?,” Theoretisch-Physikalisches Institut, Friedrich Schiller Univ., Jena, Germany, Dec. 12, 2013.
What's the (Quantum) Matter with Black Holes?,” U. Heidelberg, Theoretical Physics seminar, Heidelberg, Germany, Dec. 20, 2013.

#### Quantum Effects in Gravitational Collapse

Our Letter (with R. Vaulin of MIT Kavli Institute) was published in Physics Today. In it we explained to a general physics readership that the widespread belief that gravitational collapse leads inevitably to an event horizon need not be correct when quantum effects are taken into account. Large vacuum stresses on the horizon are the result of standard one-loop calculations of quantum fluctuations in black hole spacetimes and are a generic feature of states which approach the ordinary Minkowski vacuum far from the black hole. Moreover if quantum fluctuations and associated stress-energies do become large at the apparent horizon (defined locally) of a forming black hole, then very general arguments lead one to expect that a critical surface or phase transition should occur in its vicinity. At such a phase boundary layer the energy density of the squeezed vacuum ρV can increase very rapidly. A positive value of the vacuum energy with negative pressure pV=−ρV in the interior of a black hole” then acts as a repulsive core, preventing further collapse. The resulting stable, non-singular endpoint of complete gravitational collapse, consistent with all quantum principles is a gravitational vacuum condensate star (gravastar), so named because its interior support relies upon the energy of a vacuum condensate ρV, with the same equation of state (though with a much larger magnitude) as the cosmological dark energy believed to be pervading our universe. Once large quantum backreaction effects at the horizon are admitted, with a phase boundary layer taking its place instead, the very basis of the Hawking thermal evaporation and black hole entropy, from which all the black hole paradoxes that arise when ℏ≠0, are eliminated, and there is no enormous quantum information loss to be accounted for. This provides a testable alternative first suggested in 2001 and discussed in the last few years in the firewall” papers.

#### Lattice QCD

The Los Alamos Lattice QCD team and their collaborators are carrying out four precision studies investigating signatures of new physics at the TeV scale, elucidating the structure of the nucleon, and understanding QCD at finite temperature. Progress on these four projects is described below.

Nucleon charges and form-factors

Bhattacharya, Gupta, Yoon and their external collaborators (the PNDME collaboration) have reanalyzed the calculation of renormalization constants and the matrix elements of scalar and tensor operators to probe new physics at the TeV scale. They have revised the manuscript (arXiv:1306.5435 [hep-lat]) and submitted it for publication. They have submitted proposals for allocation of computer resources for FY15 to USQCD and XSEDE. The calculations on cluster and GPU computers at Los Alamos of the largest 64 3 × 144 lattices at the weakest coupling are continuing.

Latest Reference: Physical Review D85:5, (2012) 054512.

Matrix elements of novel CP violating operators and nEDM

Bhattacharya, Cirigliano, Gupta and Yoon are continuing to carry out the analysis of the mixing and renormalization of novel CP violating operators that contribute to the Neutron Electric Dipole Moment. They have determined an operator basis that allows for off-shell renormalization using external fixed momentum states, and a paper describing the one-loop matching between MSbar and a renormalization independent scheme is in progress. The numerical calculations of the relevant matrix elements are being done in collaboration with the RBC group using resources provided by the national USQCD initiative. Bhattacharya, Gupta, and Yoon have also started investigating the calculation of disconnected diagrams for the quark electric dipole matrix elements using clover fermions on HISQ lattices.

Latest References: Bhattacharya et al., arXiv:1212.4918 [hep-lat]; arXiv:1403.2445 [hep-lat].

Behavior of QCD at finite temperature

Bhattacharya and Gupta carried out the statistical analysis of the entire data set generated by the full HotQCD collaboration to determine the equation of state. They are developing the final analysis tools using the free software package R to make simultaneous fits to data at different N_T to extrapolate to the continuum limit with full propagation of errors. These results will be presented by Bazavov at Quark Matter 2014 and by Bhattacharya at Lattice 2014 conferences. Bhattacharya and Gupta also contributed to the analysis and writing of the manuscript on the deconfinement transition and U(1) axial anomaly being prepared for publication in PRL using domain wall fermions.

Disconnected diagrams and Transverse Momentum Distribution Functions

Bhattacharya, Gupta and Yoon, in collaboration with Michael Engelhardt, have started production runs for to investigate the signal in both connected and disconnected diagrams that will be needed to evaluate the Sivers function and other transverse momentum distribution functions using computing resources provided by USQCD at JLab.

#### Improving searches for new particles at the LHC

Graesser and LANL post-doc Tuhin Roy began a collaboration to use Q-Jets to improve searches for new physics at the LHC. Tuhin is one of the originators of the Q-Jet idea. Previous Q-Jet studies have focused on improving the efficiency to tag a hadronically-decaying W boson through improving the mass resolution and cutting on the variance in the mass variable (called volatility by the Q-Jet authors). The new element here is to apply the Q-Jet idea to the whole event, that is, to consider multiple clustering interpretations of the whole event. They are specifically looking at improving the efficiency for identifying all-hadronic top quark pairs. Any significant improvements here will have implications for BSM searches. Computations for this project are being done on LANL's Institutional Computing cluster resources.

#### Precision Cosmology Simulations

Galaxy bias, the unknown relationship between the clustering of galaxies and the underlying dark matter density field is a major hurdle for cosmological inference from large-scale structure. While traditional analyses focus on the absolute clustering amplitude of high-density regions mapped out by galaxy surveys, Warren and collaborators propose a relative measurement that compares those to the underdense regions, cosmic voids. On the basis of realistic mock catalogs they demonstrate that cross correlating galaxies and voids opens up the possibility to calibrate galaxy bias and to define a static ruler thanks to the observable geometric nature of voids.

Reference: N. Hamaus, B.D. Wandelt, P.M. Sutter, G. Lavaux, M. S. Warren, Cosmology with Void-Galaxy Correlations, Phys. Rev. Lett., 112(4):041304, 2014.

#### Quantum Field Theory and Gravity

Instability of Global de Sitter space

We (Paul R. Anderson of Wake Forest Univ. and E. M.) have shown that global de Sitter space is unstable to particle creation, even for a massive free field theory with no self-interactions. The decay rate of de Sitter space into particles may be calculated in very much analogous manner as that of a uniform, constant electric field first found by Schwinger. For de Sitter space with H2=Λ/3 , the decay rate per unit volume to scalar particles of mass M is

Γ= 8H4 π2 ln [ coth ( π M2 H2 - 94 ) ] . (1)

We studied the particle creation process in real time, computed their energy density in global 𝕊3 spatial sections, and showed that in the contracting phase they lead to an exponentially large energy density, necessitating an inclusion of their backreaction effects, which lead to large deviation of the spacetime from de Sitter space before the expanding phase can begin. These results are quite general and can be understood as also following from the effective action of the quantum conformal anomaly (2) for fields of any spin in de Sitter space, viz.

Seff = b′ 2 ∫ d4x -g { - ( □ ϕ ) 2 +2 ( Rab - 13 Rgab ) ( ∇aϕ ) ( ∇bϕ ) + ( E - 23 □ R) ϕ } (2)

where the curvature invariants E and F are given in terms of the Riemann curvature Rabcd by

E ≡ Rabcd Rabcd - 4 Rab Rab + R2 , F ≡ Rabcd Rabcd - 2 Rab Rab + 13 R2 . (3)

The field ϕ is an additional scalar degrees of freedom in the low energy effective theory of gravity, not present in the classical Einstein theory, which describes the long distance quantum correlations due to the trace anomaly.

The stress tensor derived from this effective action shows that states invariant under the O(4 ) subgroup of the de Sitter group are also unstable to perturbations of lower spatial symmetry, implying that both the O( 4,1) isometry group and its O(4 ) subgroup are broken by quantum state fluctuations. In the expanding patch a small amplitude deviation of the state in sufficiently high k modes also produces large deviations of the stress tensor at early times, emphasizing the extreme sensitivity of inflation to its initial conditions.

The main conclusion of our analysis is that the most symmetric state usually assumed in inflation is not the stable vacuum state. These results suggest that spatially inhomogeneous and/or dynamical models of cosmological dark energy within a Hubble horizon volume possessing only rotational O( 3) symmetry are relevant for determining the vacuum state and magnitude of cosmological dark energy in the universe.

These two papers have now been published in:

During this quarter the following invited talks were given:

• “New Horizons in Gravity: Dark Energy and Condensate Stars,” U. Miami, Physics Dept. seminar, Feb. 13, 2014.
• “Instability of de Sitter Space, the Schwinger Effect and Dynamical Dark Energy,” FAUST seminar, Florida Atlantic Univ., Boca Raton, FL, Feb. 24, 2014
• “What's the (Quantum) Matter with Black Holes?,” Barry Univ., Dept. of Physical Sciences, Miami Shores, FL, Feb. 26, 2014.

#### Lattice QCD

The Los Alamos Lattice QCD team and their collaborators are carrying out four precision studies investigating signatures of new physics at the TeV scale, elucidating the structure of the nucleon, and understanding QCD at finite temperature. Progress on these four projects during this quarter is described below.

Nucleon charges and form-factors

Bhattacharya, Gupta, Yoon and their external collaborators (the PNDME collaboration) finished the reanalysis of the calculation of renormalization constants and quantification of systematic errors in calculations of the matrix elements of scalar and tensor operators to probe new physics at the TeV scale. The revised manuscript (arXiv:1306.5435) with discussions of systematic errors and non-perturbative renormalization were published in Physical Review D. They also performed a first analysis of the extrapolation of lattice data to the physical point with respect to the quark mass, lattice spacing and finite volume. These results were presented by Gupta at Lattice 2014. The collaboration was awarded 20.75 M core hours on clusters at FNAL for FY15 by USQCD. Calculations on cluster and GPU computers at Los Alamos of the largest 643×144 lattices at the weakest coupling are continuing.

Latest References: Physical Review D85:5 (2012) 054512; Physical ReviewD89:9 (2014) 094502.

Matrix elements of novel CP violating operators and nEDM

Bhattacharya, Cirigliano, Gupta and Yoon have made progress on the 1-loop calculations of the mixing and renormalization of novel CP violating operators that contribute to the Neutron Electric Dipole Moment. They have established an operator basis that allows for off-shell renormalization using external fixed momentum states, and a paper describing the one-loop matching between MSbar and a renormalization independent scheme is in progress. The numerical calculations of the relevant matrix elements are being done in collaboration with the RBC group using resources provided by the national USQCD initiative. Bhattacharya, Gupta, and Yoon have made progress on calculation of matrix elements involving disconnected diagrams for the quark electric dipole moment operator using clover fermions on HISQ lattices and preliminary results were presented by Yoon at Lattice 2014.

Latest References: Bhattacharya et al., arXiv:1212.4918; arXiv:1403.2445

Behavior of QCD at finite temperature

Bhattacharya and Gupta carried out the statistical analysis of the entire data set generated by the full HotQCD collaboration to determine the equation of state. They are developing the final analysis tools using the free software package R to make simultaneous fits to data at different points to extrapolate to the continuum limit with full propagation of errors. These results were presented by Bazavov at Quark Matter 2014 and by Bhattacharya at Lattice 2014 conferences. The final paper is being written. Bhattacharya and Gupta also contributed to the analysis and writing of the manuscript on the deconfinement transition and U(1) axial anomaly being prepared for publication in PRL using domain wall fermions.

Disconnected diagrams and Transverse Momentum Distribution Functions

Bhattacharya, Gupta, Yoon and collaborator Michael Engelhardt at NMSU, are carrying out production runs for calculating matrix elements to evaluate the Sivers function and other transverse momentum distribution functions using computing resources provided by USQCD at JLab. Engelhardt presented these results at Lattice 2014. Bhattacharya, Gupta and Yoon have investigated methods to speed up the calculation of disconnected diagrams and improve the signal. Yoon presented these results at lattice 2014, which included the first results for the quark electric dipole moment operator that contributes to nEDM.

#### Neutrinoless double β decay and the LHC

The idea here is to explore what kinds of BSM physics can give rise to a neutrinoless double $\beta$ decay signal, that is not in the form of a Majorana neutrino mass. If at the scale of an 0νββ experiment the only effect of BSM physics—other than a possible Majorana neutrino mass—occurs through higher-dimension operators, then one can enumerate all the leading order possibilities. For a 0νββ signal the leading-order operators are dimension 9 and involve 4 quarks and two same-signed leptons. Graesser initiated a collaboration with Vincenzo Cirigliano (Los Alamos NP), Mark Wise (Caltech) and Yue Zhang (Caltech) to create renormalizable models that have a non-Majorana mass 0νββ signal. Preliminary estimates indicate that the scale suppressing these higher dimension operators can be O(TeV) and still give an appreciable signal in 0νββ. This estimate therefore suggests that constraints from LHC and LEP may be important. They will investigate constraints on these models from the LHC arising from same-signed dilepton and leptoquark searches, as well as those bounds from LEP and the LHC on 4-Fermi contact operators.

#### Precision Cosmology Simulations

On April 18--19, 2014, Warren ran the ds14a cosmological simulation using the 2HOT code with 1,073,741,824,000 (102403) particles on 12,288 nodes (196,608 CPU cores and 12,288 NVIDIA K20x GPUs) of the Titan system at Oak Ridge National Laboratory. This is one of the largest computations ever performed in any field of science. The simulation was of a cubical region of space 8,000 Mpc/h across; a region large enough to contain the entire visible Universe older than 2.8 billion years in a light cone to a redshift of 2.3 for an observer at the center of the simulation volume. The simulation carried out 3.14×1020 floating point operations (0.3 zettaflops). We saved 16 particle dumps totaling 540 Terabytes. Had we attempted the same calculation with a simple O(N2) algorithm, it would have taken about ten million times as many operations and approximately 37 thousand years on the same hardware to obtain the answer. During the initial stages of the simulation, a single timestep required about 110 seconds, for a performance of 5.9 Petaflops.

#### Quantum Field Theory and Gravity

Fermion Pairing and the Scalar Boson of the 2D Conformal Anomaly

With D. Blaschke (recipient of an APART fellowship of the Austrian Academy of Sciences) and R. Carballo-Rubio (a Ph. D. student at the Univ. of Granada, Spain, who visited LANL through a CSIC grant from Spain) we have analyzed the phenomenon of fermion pairing into an effective boson, which is associated with anomalies and the anomalous commutators of currents bilinear in the fermion fields. A well-known example is the chiral bosonization of the Schwinger model, determined by the axial current anomaly of massless Dirac fermions in two spacetime dimensions. We showed by both functional and Fock space operator methods that a similar bosonized description applies to the 2D conformal trace anomaly of the fermion stress tensor. For both the chiral and conformal anomalies, correlation functions involving anomalous currents,jμ5 o Tμν of massless fermions exhibit a massless boson 1/k2 pole, and the associated spectral functions obey a UV finite sum rule, becoming δ-functions in the massless limit. In both cases the corresponding effective action of the anomaly is non-local, but may be expressed in a local form by the introduction of a new bosonic field, which becomes a bona fide propagating quantum field in its own right. In both cases this is expressed in Fock space by the anomalous Schwinger commutators of currents becoming the canonical commutation relations of the corresponding boson, which has a operator realization as a coherent superposition of massless fermion pairs, and which saturate the intermediate state sums in quantum correlation functions of fermion currents. Further consequences of this mapping of fermion pairs to bosons are that the Casimir energy of fermions on a finite spatial interval [0,L] can be described as a coherent scalar condensation of pairs, and by an algebraic identity the one-loop correlation functions of arbitrary numbers of fermion stress tensors ⟨TTT…⟩may be expressed as a combinatoric sum of purely linear tree diagrams of the scalar boson. This paper is now ready for submission to JHEP.

During this quarter the following invited talks were given:

• “New Horizons in Gravity: Dark Energy and Condensate Stars,” Univ. of Texas, Austin, TX, April 15, 2014.
• “The Instability of the de Sitter Vacuum,” Univ. of Texas, Austin, TX, April 17, 2014.
• “New Horizons in Gravity: Dark Energy and Condensate Stars,” Univ. of California, Berkeley, CA, May 21, 2014.

#### Lattice QCD

The Los Alamos Lattice QCD team and their collaborators are carrying out precision studies investigating signatures of new physics at the TeV scale, elucidating the structure of the nucleon, and understanding QCD at finite temperature. Progress during this quarter on the four projects being pursued are described below.

Nucleon charges and form-factors

Results of the calculation of renormalization constants and quantification of systematic errors in calculations of the matrix elements of scalar and tensor operators to probe new physics at the TeV scale were presented by Gupta at Lattice 2014 and Solvay Conference in Brussels in Sept 2014. Bhattacharya, Gupta and Yoon are extending the simulations to finer lattices to quantify discretization errors and improve the extrapolation to the continuum limit. The collaboration was awarded 20.75 M core hours on clusters at FNAL for FY15 by USQCD which are being used to increase the statistics. On the cluster and GPU computers at Los Alamos, they are simulating the largest 643×144 lattices at the weakest coupling.

Latest References: Physical Review D85:5 (2012) 054512; Physical Review D89:9 (2014) 094502.

Matrix elements of novel CP violating operators and nEDM

Bhattacharya, Cirigliano, Gupta and Yoon continue to make progress on the 1-loop calculations of the mixing and renormalization of novel CP violating operators of dimension-5 that contribute to the Neutron Electric Dipole Moment. They have established an operator basis that allows for off-shell renormalization using external fixed momentum states, and a paper describing the one-loop matching between MSbar and a renormalization independent scheme is in progress. The numerical calculations of the relevant matrix elements are being done in collaboration with the RBC group using resources provided by the national USQCD initiative. Bhattacharya, Gupta, and Yoon have made progress on calculation of matrix elements involving disconnected diagrams for the quark electric dipole moment operator using clover fermions on HISQ lattices and preliminary results were presented by Yoon at Lattice 2014.

Latest References: Bhattacharya et al., arXiv:1212.4918; arXiv:1403.2445

Behavior of QCD at finite temperature

Bhattacharya and Gupta carried out the statistical analysis of the entire data set generated by the full HotQCD collaboration to determine the equation of state. They also developed the final analysis tools using the free software package R to make simultaneous fits to data at different NT to extrapolate to the continuum limit with full propagation of errors. These results were presented by Bazavov at Quark Matter 2014 and by Bhattacharya at Lattice 2014 conferences. The final paper has been accepted for publication to Physical Review D. Bhattacharya and Gupta also contributed to the analysis and writing of the manuscript on the deconfinement transition and U(1) axial anomaly using domain wall fermions that was published in Physical Review Letters 113 (2014) 082001. They are now investigating the fluctuation of conserved charges (Electric charge, strangness, baryon number) near the transition to probe the possible critical end-point at finite chemical potential.

Disconnected diagrams and Transverse Momentum Distribution Functions

Bhattacharya, Gupta, Yoon and collaborator Michael Engelhardt at NMSU, are carrying out production runs for calculating matrix elements to evaluate the Sivers function and other transverse momentum distribution functions using computing resources provided by USQCD at JLab. Engelhardt presented these results at Lattice 2014. Bhattacharya, Gupta and Yoon have investigated methods to speed up the calculation of disconnected diagrams and improve the signal. Yoon presented these results at lattice 2014, which included the first results for the quark electric dipole moment operator that contributes to nEDM.

#### Dark matter and the LHC

The preprint arXiv:1311.5886 [hep-ph], by Cirigliano, Graesser, Ovanesyan, and Shoemaker, has now being accepted for publication in Phys. Lett. B.

Work by Graesser and Jessie Shelton presented in Phys. Rev. Lett. 111 (2013) 121802 proposed a new kinematic variable (topness) designed to improve the sensitivity of the LHC experiments to top squark production, with top squarks decaying to tb+MET and tt+MET final states. Their topness variable is now being used by the ATLAS experiment in their search for top squark production (arXiv:1407.0583 [hep-ex]), with the top squarks decaying to those final states. The ATLAS search (arXiv:1410.4031 [hep-ex]) looking for production of dark matter that predominately couples to top quarks also uses the topness variable.

Graesser continues to work on several projects with Jessie Shelton, Tuhin Roy (now at TATA) and LANL post-doc Jinrui Huang, using LANL's cluster computing resources. These projects are aimed at improving the sensitivity of the LHC to beyond-the-Standard Model physics appearing in final states having significant top quark backgrounds.

Huang and collaborators Tao, Yu, and Wang continue their exploration of the nearly Peccei-Quinn symmetric limit shared by common singlet extensions of the Minimal Supersymmetric Standard Model, that was initiated in arXiv:1309.6633 [hep-ph], Phys. Rev. Lett. 112 (2014) 221803. This limit has been established as a viable framework for studying sub-electroweak scale dark matter phenomenology and has interesting and direct connections to new exotic Higgs decay physics. In arXiv:1407.0038 [hep-ph] they discuss benchmark models in this framework that accommodate the Galactic Center gamma ray excess. They emphasize connections between the phenomenology of dark matter direct detection, indirect detection, and new exotic decay channels for the 125 GeV Higgs boson decays to h→ττMET and h→bbMET final states. They estimate the sensitivity at the LHC for rare Higgs boson decay modes. This preprint has been accepted for publication in Phys. Rev. D.

#### Precision Cosmology Simulations

The "Dark Sky Simulations: Early Data Release" paper by Skillman & Warren et al. was submitted to Computational Science & Discovery, and the data and analysis software was made publicly available at http://darksky.slac.stanford.edu. Work continues on Titan at Oak Ridge testing independent timestep code modifications to support the high resolution ds14b simulation.

#### Supernova neutrino oscillations

Friedland and collaborators have continued studying the rich and complicated dynamics of neutrino flavor transformations inside a supernova and its implications for the design of future neutrino detectors.

On the theoretical front, it was realized that, while all existing calculations of collective oscillations in a supernova assume flavor universality, small deviations from universality could in fact have a big impact on the outcome of the calculations. To quantify this effect, Friedland and E. Passemar (LANL postdoc, now faculty at Indiana U) have computed non-universal contributions to the MSW potentials induced by loop effects. The computation is completed and two papers – one on the physics of the calculations and one on its impact on the oscillation dynamics – are in preparation.

On the experimental front, the spectra obtained in the simulations were put in the simulation software for the future liquid argon and water Cherenkov detectors. This work, done in collaboration with Kate Scholberg (Duke U) and Michael Smy (UC Irvine), demonstrated that prominent nonthermal spectral features can indeed be seen a large liquid argon detector, while in a water-Cherenkov detectors they are completely washed out due to the inherently poor energy resolution. The results were presented at the August LBNE collaboration meeting at Fermilab.

#### New physics in the neutrino sector

In collaboration with postdocs J. Cherry and I. Shoemaker, Friedland has been developing a framework of nonstandard neutrino interactions that arise from neutrino mixing with a new secluded sector. It has been found that the presence of this new physics could be probed with the Ultra-High-Energy neutrinos recently observed by the Icecube collaboration. It was further noted that the scale of the masses in the secluded sector naturally coincides with the values favored by models of self-interacting dark matter. The signatures of this mechanism and its possible connection to the dark matter sector are currently being explored. Preliminary results were presented by J. Cherry at the MIAPP neutrino workshop in Garching, Germany.

In addition to the LBNE collaboration meeting presentation, Friedland has also given a lecture at The 2014 International Summer School on AstroComputing (UCSD, July 2014) and an overview talk on supernova neutrino oscillations at the MIAPP neutrino workshop in Garching, Germany