Tanmoy Bhattacharya
Michael L. Graesser
Rajan Gupta
Michael S. Warren
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, Novel CP violating operator's contribution to nEDM, elucidating the structure of the nucleon, and understanding QCD at finite temperature. Progress during this quarter on these projects is described below.
Nucleon charges and form-factors
Results of isovector charges gA, gS and gT from the 2+1+1-flavor clover-on-HISQ calculations were published in PRD. The analysis of isovector charges using the 2+1-flavor clover-on-clover lattice QCD formulation was completed, a manuscript for publication was prepared and submitted to the arXiv. The four ensembles of clover-on-clover were simulated on the Titan computer at Oak Ridge under the ALCC program. The clover-on-clover calculation has the advantage of being based on a unitary lattice formulation, and provides an important check on the 2+1+1-flavor clover-on-HISQ calculations. We are continuing the analysis of a second physical mass HISQ ensemble with lattice size 963 ×192 at 0.06 fm on cluster and GPU computers at Los Alamos and using ERCAP allocations at NERSC. Proceedings of talks given at Lattice 2016 were prepared for publication. The analysis of electric, magnetic and axial form factors using 2-state fits has been carried out and these results were also presented at Lattice 2016 by post-doc Yong-Chull Jang. Manuscripts describing these results are being prepared for publication.
Recent References:
arXiv:1611.07452
Physical Review D94:5 (2016) 054508
Physical Review D93:11 (2016) 114506
arXiv:1601.01730
Physical Review D92:9 (2015) 094511
Physical Review D89:9 (2014) 094502
Physical Review D85:5 (2012) 054512
Matrix elements of novel CP violating operators and nEDM
Calculations of the matrix elements of the quark chromo electric dipole moment operator and mixing with the pseudoscalar operator are ongoing. The formalism for these calculations and new numerical techniques are being developed. Status of results were presented at Lattice 2016 by Bhattacharya and at CONF12 by Gupta. Codes to calculate the disconnected diagrams and the reweighting factor were developed and production runs started. The paper with 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 was published in PRD. In this paper Bhattacharya, Cirigliano, Gupta and Yoon calculate the operator basis that allows for off-shell renormalization using external fixed momentum states. The paper describing the one-loop matching between MSbar and a renormalization independent scheme was completed and paper describing these calculations was also published in PRD. A second paper with calculations of the quark electric dipole moment (tensor charges of the up, down and strange quarks within the neutron), their contribution to the neutron electric dipole moment and implications for split SUSY models was published in PRL.
Latest References: Bhattacharya et al.,
arXiv:1701.04132
arXiv:1612.08438
arXiv:1601.02264
Physical Review D92:9 (2015) 114026
Physical Review Letters 112:21 (2015) 212002
arXiv:1502.07325
arXiv:1403.2445
arXiv:1212.4918
Disconnected diagrams
The matrix elements of iso-scalar and flavor diagonal operators are needed for the analysis of a number of interesting qualities such as the nucleon electric dipole moment, the nucleon sigma term, and the strangeness content of the proton. These matrix elements get contributions from disconnected diagrams, that are computationally challenging to compute with high precision. Bhattacharya, Gupta and Yoon, in collaboration with Gambhir, Orginos and Stathopoulos at William and Mary are using a new method based on deflation and hierarchical probing to speed up the calculation of disconnected diagrams. First results were presented by Gambhir at Lattice2016.
References:
arXiv:1611.01193
Transverse Momentum Distribution Functions
A manuscript with results for the Sivers and Boer-Mulders shift, the transversity and the generalized worm-gear shift for two different fermion discretization schemes is in final stages of preparation. Gupta presented these results at the POETIC7, Philadelphia, November, 2016 meeting. Bhattacharya, Gupta, Yoon and collaborator Michael Engelhardt at NMSU are continuing production runs for calculating matrix elements to evaluate the Sivers function and other transverse momentum distribution (TMD) functions using computing resources provided by USQCD at JLab.
Latest References:
arXiv:1611.01193
arXiv:1601.05717
Behavior of QCD at finite temperature
The HotQCD collaboration is continuing to investigate fluctuations of conserved charges (electric charge, strangeness, baryon number) around the transition temperature (140–160 MeV) to investigate the behavior of QCD near the possible critical end-point at finite chemical potential that will be probed by the Beam Energy Scan run II.
Latest References:
Physical Review D90 (2014) 094503
Physical Review Letters 113 (2014) 082001
Physical Review D86 (2012) 034509
Physical Review D86 (2012) 094503
Physical Review D85 (2012) 054503
Dark Matter and LHC Physics
In this quarter Graesser worked on a number of ongoing projects and started several new ones. He and Yue Zhang (Northwestern U.) are investigating the phenomenological implications of scenario of dark matter in which the dark matter is light, i.e., less than a GeV, and the mediator is a pseudo-scalar. That the mediator is a pseudo-scalar leads to a qualitatively different phenomenology than previously discussed in the literature. They have been investigating the phenomenological effect on such interactions on the MiniBoone experiment. Graesser and Shashank Shalgar (Los Alamos) are investigating the impact that interactions between dark matter and either photons or neutrinos can have on the dark matter power spectrum and the cosmic microwave background.
Graesser is also working on a number of projects using 8 and 13 TeV LHC data to constrain models of TeV scale physics. These projects includes studying models having light stops and models that lead at low-energies to novel signatures of neutrinoless double beta decay. Graesser is also collaborating with Tuhin Roy (TATA Institute, Mumbai, India) on a new method to improve the sensitivity of the LHC to new TeV-scale physics. Graesser is collaborating with D. Kang and B. Yoon on applying deep learning methods, used in image classification, to improve the sensitivity of the LHC to a boosted W'.
Latest References:
Physics Letters B749 (2014) 293
arXiv:1311.2028
Physical Review Letters111 (2013) 121802
JHEP 1302(2013) 046
JHEP 1210(2012) 025
Physics Letters B714 (2012) 267
Physics Review D85 (2012) 054512
arXiv:1107.2666
JHEP 1110(2011) 110
Neutrinoless double beta decay
Graesser is collaborating with V. Cirigliano, W. Dekens and E. Mereghetti on using chiral SU(3) to estimate the size of Delta L=2 hadronic matrix elements between two pions, that are relevant to short-distance Beyond-the-Standard-Model contributions to a neutrinoless double beta decay signal. Using chiral SU(3) perturbation theory, these matrix elements can be related to kaon-anti-kaon and K->pi pi matrix elements, which have been computed using lattice QCD.
Latest References:
arXiv:1606.04549
Precision Cosmology Simulations
The "Dark Sky Simulations: Early Data Release" paper by Skillman & Warren et al. (arXiv:1407.2600) is the first published N-body simulation results with over a trillion particles. The the data and analysis software made publicly available at http://darksky.slac.stanford.edu. Analysis of a higher resolution simulation on Titan at Oak Ridge with (10240**3) particles and 1/h Gpc box is underway. The calculation involves one zettaflops integrated and will generate one petabyte of data. It will be the highest resolution cosmological simulation of dark matter, mass function, power spectrum, galaxy halo merger history.
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, Novel CP violating operator's contribution to nEDM, elucidating the structure of the nucleon, and understanding QCD at finite temperature. Progress during this quarter on these projects is described below.
Nucleon charges and form-factors
Results of isovector charges gA, gS and gT from the 2+1-flavor clover-on-clover calculations were published in PRD. We are continuing the analysis of a second physical mass HISQ ensemble with lattice size 963 ×192 at 0.06 fm on cluster and GPU computers at Los Alamos and using ERCAP allocations at NERSC. The analysis of electric, magnetic and axial form factors using 2-state fits was carried out and manuscripts for publication were drafted and are in their final stages for publication.
Recent References:
Physical Review D95:5 (2017) 074508
Physical Review D94:5 (2016) 054508
Physical Review D93:11 (2016) 114506
arXiv:1601.01730
Physical Review D92:9 (2015) 094511
Physical Review D89:9 (2014) 094502
Physical Review D85:5 (2012) 054512
Matrix elements of novel CP violating operators and nEDM
Calculations of the matrix elements of the quark chromo electric dipole moment operator and mixing with the pseudoscalar operator are ongoing. The formalism for these calculations and new numerical techniques are being developed. Status of results were presented at Lattice 2016 by Bhattacharya and at CONF12 by Gupta. Codes to calculate the disconnected diagrams and the reweighting factor were developed and production runs started. The paper with 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 was published in PRD. In this paper Bhattacharya, Cirigliano, Gupta and Yoon calculate the operator basis that allows for off-shell renormalization using external fixed momentum states. The paper describing the one-loop matching between MSbar and a renormalization independent scheme was completed and paper describing these calculations was also published in PRD. A second paper with calculations of the quark electric dipole moment (tensor charges of the up, down and strange quarks within the neutron), their contribution to the neutron electric dipole moment and implications for split SUSY models was published in PRL.
Latest References: Bhattacharya et al.,
arXiv:1701.04132
arXiv:1612.08438
arXiv:1601.02264
Physical Review D92:9 (2015) 114026
Physical Review Letters 112:21 (2015) 212002
arXiv:1502.07325
arXiv:1403.2445
arXiv:1212.4918
Disconnected diagrams
The matrix elements of iso-scalar and flavor diagonal operators are needed for the analysis of a number of interesting qualities such as the nucleon electric dipole moment, the nucleon sigma term, and the strangeness content of the proton, and the interaction of dark matter with nucleons. These matrix elements get contributions from disconnected diagrams, that are computationally challenging to compute with high precision. Bhattacharya, Gupta and Yoon, in collaboration with Gambhir, Orginos and Stathopoulos at William and Mary are using a new method based on deflation and hierarchical probing to speed up the calculation of disconnected diagrams. First results were presented by Gambhir at Lattice2016. A manuscript describing the results is being prepared for publication.
References:
arXiv:1611.01193
Transverse Momentum Distribution Functions
A manuscript with results for the Sivers and Boer-Mulders shift, the transversity and the generalized worm-gear shift for two different fermion discretization schemes is in final stages of preparation. Gupta presented these results at the POETIC7, Philadelphia, November, 2016 meeting.
Latest References:
arXiv:1611.01193
arXiv:1601.05717
Behavior of QCD at finite temperature
The HotQCD collaboration is continuing to investigate fluctuations of conserved charges (electric charge, strangeness, baryon number) around the transition temperature (140–160 MeV) to investigate the behavior of QCD near the possible critical end-point at finite chemical potential that will be probed by the Beam Energy Scan run II.
Latest References:
Physical Review D90 (2014) 094503
Physical Review Letters 113 (2014) 082001
Physical Review D86 (2012) 034509
Physical Review D86 (2012) 094503
Physical Review D85 (2012) 054503
Dark Matter and LHC Physics
In this quarter, Graesser has been continuing his work with Tuhin Roy (TATA) and Arun Thalapillil (Pune) on improving the sensitivity of the LHC to new TeV-scale physics scenarios. Graesser continues to collaborate with D. Kang and B. Yoon (LANL) on applying deep learning methods to improve the sensitivity of the LHC to new physics scenarios.
Latest References:
Physics Letters B749 (2014) 293
arXiv:1311.2028
Physical Review Letters111 (2013) 121802
JHEP 1302(2013) 046
JHEP 1210(2012) 025
Physics Letters B714 (2012) 267
Physics Review D85 (2012) 054512
arXiv:1107.2666
JHEP 1110(2011) 110
Neutrinoless double beta decay
In this quarter Graesser has been working with Vincenzo Cirigliano, Wouter Dekens and Emanuele Mereghetti (LANL) on a couple of projects related to phenomenological signals of neutrinoless double beta decay. In 1701.01442 (Phys. Lett B769 (2017) 460-464), the authors use SU(3) chiral perturbation theory to provide a first estimate of the two-pion matrix element of all Delta I=2 Lorentz scalar 4-quark operators that contribute to a Delta L=2 neutrinoless double beta decay signal, arising from short distance physics. The authors relate the two-pion matrix element to the kaon-anti-kaon matrix elements, as well as K-> 2 pi, which have been computed accurately using lattice QCD. SU(3) breaking effects due to meson mass splitting occurs at next-to-leading chiral order and based on a one-loop computation the authors estimate the size of those corrections to be of O(20%-30%). Long distance pion exchange can give the leading contribution to neutrinoless double beta signal arising from short distance physics scenarios, and the two - pion matrix element is an important input to that process.
Graesser, together with Cirigliano, Dekens and Mereghetti are investigating the phenomenology of dimension-7 operators which can also contribute to a Delta L=2 neutrinoless double beta decay signal.
Latest References:
Physics Letters B769 (2017) 460
arXiv:1606.04549
Precision Cosmology Simulations
The "Dark Sky Simulations: Early Data Release" paper by Skillman & Warren et al. (arXiv:1407.2600) is the first published N-body simulation results with over a trillion particles. The the data and analysis software made publicly available at http://darksky.slac.stanford.edu. Analysis of a higher resolution simulation on Titan at Oak Ridge with (10240**3) particles and 1/h Gpc box is underway. The calculation involves one zettaflops integrated and will generate one petabyte of data. It will be the highest resolution cosmological simulation of dark matter, mass function, power spectrum, galaxy halo merger history.
Pedro Machada from Fermilab and Daniele Alvez from New York University have accepted LANL's offer for staff scientist positions and will join us in Fall, 2017.
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, Novel CP violating operator's contribution to nEDM, elucidating the structure of the nucleon, and understanding QCD at finite temperature. Progress during this quarter on these projects is described below.
Nucleon charges and form-factors
New results of isovector and flavor-diagonal charges gA, gS and gT from the 2+1+1-flavor clover-on-HISQ calculations were obtained and presented at Lattice 2017 by R. Gupta. These are being prepared for publication. We are continuing increasing the statistics and improving the analysis of a second physical mass HISQ ensemble with lattice size 963 ×192 at 0.06 fm on cluster and GPU computers at Los Alamos and using ERCAP allocations at NERSC. The analysis of electric, magnetic and axial vector form factors using 2-state fits was carried out for both the 2+1+1-flavor clover-on-HISQ and 2+1-flavor clover on clover lattice QCD formulations. The results were presented by Yong-Chull Jang at Lattice 2017. Results for the axial vector form factors from the 2+1+1-flavor clover-on-HISQ have been published [arXiv:1705.06834]. Three additional manuscripts for publication are being drafted and final stages of the analysis is being carried out.
Relevant References:
arXiv:1705.06834
Physical Review D95:5 (2017) 074508
Physical Review D94:5 (2016) 054508
Physical Review D93:11 (2016) 114506
arXiv:1601.01730
Physical Review D92:9 (2015) 094511
Physical Review D89:9 (2014) 094502
Physical Review D85:5 (2012) 054512
Matrix elements of novel CP violating operators and nEDM
Calculations of the matrix elements of the quark chromo electric dipole moment operator and mixing with the pseudoscalar operator are ongoing. The formalism for these calculations and new numerical techniques are being developed. Status of results were presented at Lattice 2016 by Bhattacharya and at CONF12 by Gupta. Codes to calculate the disconnected diagrams and the reweighting factor were developed and production runs started. The paper with 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 was published in PRD. In this paper Bhattacharya, Cirigliano, Gupta and Yoon calculate the operator basis that allows for off-shell renormalization using external fixed momentum states. The paper describing the one-loop matching between MSbar and a renormalization independent scheme was completed and paper describing these calculations was also published in PRD. A second paper with calculations of the quark electric dipole moment (tensor charges of the up, down and strange quarks within the neutron), their contribution to the neutron electric dipole moment and implications for split SUSY models was published in PRL. The status of these calculations was presented by Boram Yoon at a plenary talk at Lattice 2017.
Relevant References:
arXiv:1701.04132
arXiv:1612.08438
arXiv:1601.02264
Physical Review D92:9 (2015) 114026
Physical Review Letters 112:21 (2015) 212002
arXiv:1502.07325
arXiv:1403.2445
arXiv:1212.4918
Disconnected diagrams
The matrix elements of iso-scalar and flavor diagonal operators are needed for the analysis of a number of interesting qualities such as the nucleon electric dipole moment, the nucleon sigma term, and the strangeness content of the proton, and the interaction of dark matter with nucleons. These matrix elements get contributions from disconnected diagrams, that are computationally challenging to compute with high precision. Bhattacharya, Gupta and Yoon, in collaboration with Gambhir, Orginos and Stathopoulos at William and Mary are using a new method based on deflation and hierarchical probing to speed up the calculation of disconnected diagrams. Results from a comprehensive analysis were presented by Gupta at Lattice2017. A manuscript describing the results is being prepared for publication.
Relevant References:
arXiv:1611.01193
Transverse Momentum Distribution Functions
The manuscript with results for the Sivers and Boer-Mulders shift, the transversity and the generalized worm-gear shift for two different fermion discretization schemes has been submitted for publication [arXiv:1706.03406]. Gupta has presented these results at the POETIC7, Philadelphia, November, 2016 meeting.
Relevant References:
arXiv:1706.03406
arXiv:1611.01193
arXiv:1601.05717
Behavior of QCD at finite temperature
The HotQCD collaboration is continuing to investigate fluctuations of conserved charges (electric charge, strangeness, baryon number) around the transition temperature (140–160 MeV) to investigate the behavior of QCD near the possible critical end-point at finite chemical potential that will be probed by the Beam Energy Scan run II.
Relevant References:
Physical Review D90 (2014) 094503
Physical Review Letters 113 (2014) 082001
Physical Review D86 (2012) 034509
Physical Review D86 (2012) 094503
Physical Review D85 (2012) 054503
Dark Matter and LHC Physics
Graesser is continuing his work with Tuhin Roy (TATA) and Arun Thalapillil (Pune) on improving the sensitivity of the LHC to new TeV-scale physics scenarios. Graesser continues to collaborate with D. Kang and B. Yoon (LANL) on applying deep learning methods to improve the sensitivity of the LHC to new physics scenarios.
Relevant References:
Physics Letters B749 (2014) 293
arXiv:1311.2028
Physical Review Letters111 (2013) 121802
JHEP 1302(2013) 046
JHEP 1210(2012) 025
Physics Letters B714 (2012) 267
Physics Review D85 (2012) 054512
arXiv:1107.2666
JHEP 1110(2011) 110
Neutrinoless double beta decay
Graesser, together with Cirigliano, Dekens and Mereghetti (LANL) and de Vries (Niken) have been investigating the phenomenology of dimension-7 operators which can also contribute to a Delta L=2 neutrinoless double beta decay signal. Dimension-7 Delta L=2 operators are the next-leading order contribution after the dimension-5 Weinberg operator. They have classified the operators and evolved them to the electroweak scale where such operators are matched onto dimension-6, -7 and -9 operators. They then evolve the effective operators to the QCD scale and construct the chiral effective theory for such operators, and derive the two-nucleon neutrinoless double beta decay currents up to leading order in the chiral counting. They find the neutrinoless double beta decay amplitude to depend on only a relatively few number of nuclear matrix elements. Some phenomenology of the dependence of the differential decay rate on the neutrino mass and dimension-7 operator Wilson coefficients, as well as different methods to compute the nuclear matrix elements, is discussed
Relevant References:
Physics Letters B769 (2017) 460
arXiv:1606.04549
Precision Cosmology Simulations
The "Dark Sky Simulations: Early Data Release" paper by Skillman & Warren et al. (arXiv:1407.2600) is the first published N-body simulation results with over a trillion particles. The the data and analysis software made publicly available at http://darksky.slac.stanford.edu. Analysis of a higher resolution simulation on Titan at Oak Ridge with (10240**3) particles and 1/h Gpc box is underway. The calculation involves one zettaflops integrated and will generate one petabyte of data. It will be the highest resolution cosmological simulation of dark matter, mass function, power spectrum, galaxy halo merger history.
Team Members: Daniele Alves, Tanmoy Bhattacharya, Michael L. Graesser, Rajan Gupta, Michael S. Warren
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, Novel CP violating operator's contribution to nEDM, elucidating the structure of the nucleon, and understanding QCD at finite temperature. Progress during this quarter on these projects is described below.
Nucleon charges and form-factors
Extensive additional simulations of isovector and flavor-diagonal charges gA, gS and gT from the 2+1+1-flavor clover-on-HISQ calculations are almost complete and preliminary results were presented by R. Gupta at Lattice 2017. The most time consuming of the ongoing calculations is the analysis of a second physical mass HISQ ensemble with lattice size 963 ×192 at 0.06 fm on cluster and GPU computers at Los Alamos and using ERCAP allocations at NERSC. The analysis of electric, magnetic and axial vector form factors using 2-state fits was carried out for both the 2+1+1-flavor clover-on-HISQ and 2+1-flavor clover on clover lattice QCD formulations. These results have been extended to 3-state analysis and were presented by Yong-Chull Jang at Lattice 2017. Both talks at Lattice 2017 are being prepared for publication. Results for the axial vector form factors from the 2+1+1-flavor clover-on-HISQ have been published in arXiv:1705.06834 and are in the final stages of review by PRD. The final analysis of our 2+1+1-flavor clover-on-HISQ calculations is being carried out and the writing of three manuscripts for publication was initiated.
Relevant References:
arXiv:1705.06834
Physical Review D95:5 (2017) 074508
Physical Review D94:5 (2016) 054508
Physical Review D93:11 (2016) 114506
arXiv:1601.01730
Physical Review D92:9 (2015) 094511
Physical Review D89:9 (2014) 094502
Physical Review D85:5 (2012) 054512
Matrix elements of novel CP violating operators and nEDM
Calculations of the matrix elements of the quark chromo electric dipole moment operator and mixing with the pseudoscalar operator are ongoing. The formalism for these calculations and new numerical techniques are being developed. Status of results were presented at Lattice 2016 by Bhattacharya and at CONF12 by Gupta. Production runs for disconnected diagrams and the reweighting factor have started. Theoretical and numerical investigations of the operator mixing are being carried out. The status of these calculations was presented by Boram Yoon in the plenary talk on the calculation of matrix elements of novel CP violating operators and nEDM at Lattice 2017.
Relevant References:
arXiv:1701.04132
arXiv:1612.08438
arXiv:1601.02264
Physical Review D92:9 (2015) 114026
Physical Review Letters 112:21 (2015) 212002
arXiv:1502.07325
arXiv:1403.2445
arXiv:1212.4918
Disconnected diagrams
The matrix elements of iso-scalar and flavor diagonal operators are needed for the analysis of a number of interesting qualities such as the nucleon electric dipole moment, the nucleon sigma term, and the strangeness content of the proton, and the interaction of dark matter with nucleons. These matrix elements get contributions from disconnected diagrams, that are computationally challenging to compute with high precision. Bhattacharya, Gupta and Yoon are preparing a manuscript describing the results in collaboration with Gambhir, Orginos and Stathopoulos at William and Mary. They are also continuing to develop a new method based on deflation and hierarchical probing to speed up the calculation of disconnected diagrams.
Relevant References:
arXiv:1611.01193
Transverse Momentum Distribution Functions
Prepared and published results for the Sivers and Boer-Mulders shift, the transversity and the generalized worm-gear shift for two different fermion discretization schemes [arXiv:1706.03406]. Addressed the referee's comments. Paper accepted for publication in PRD.
Relevant References:
arXiv:1706.03406
arXiv:1611.01193
arXiv:1601.05717
Behavior of QCD at finite temperature
Investigated the properties of QCD at finite temperature, including the nature of the transition, the equation of state and the fluctuations of conserved charges (electric charge, strangeness, baryon number) around the transition temperature (140–160 MeV) as part of the HOTQCD collaboration. The five publications have over 2100 citations.
Relevant References:
Physical Review D90 (2014) 094503
Physical Review Letters 113 (2014) 082001
Physical Review D86 (2012) 034509
Physical Review D86 (2012) 094503
Physical Review D85 (2012) 054503
Dark Matter and LHC Physics
Graesser is continuing his work with Tuhin Roy (TATA) and Arun Thalapillil (Pune) on improving the sensitivity of the LHC to new TeV-scale physics scenarios. Graesser continues to collaborate with D. Kang and B. Yoon (LANL) on applying deep learning methods to improve the sensitivity of the LHC to new physics scenarios.
Relevant References:
Physics Letters B749 (2014) 293
arXiv:1311.2028
Physical Review Letters111 (2013) 121802
JHEP 1302(2013) 046
JHEP 1210(2012) 025
Physics Letters B714 (2012) 267
Physics Review D85 (2012) 054512
arXiv:1107.2666
JHEP 1110(2011) 110
Neutrinoless double beta decay
Graesser, together with Cirigliano, Dekens and Mereghetti (LANL) and de Vries (Niken) have been investigating the phenomenology of dimension-7 operators which can also contribute to a Delta L=2 neutrinoless double beta decay signal. Dimension-7 Delta L=2 operators are the next-leading order contribution after the dimension-5 Weinberg operator. They have classified the operators and evolved them to the electroweak scale where such operators are matched onto dimension-6, -7 and -9 operators. They then evolve the effective operators to the QCD scale and construct the chiral effective theory for such operators, and derive the two-nucleon neutrinoless double beta decay currents up to leading order in the chiral counting. They find the neutrinoless double beta decay amplitude to depend on only a relatively few number of nuclear matrix elements, which can be lifted from the existing literature. Some phenomenology of the dependence of the differential decay rate on the neutrino mass and dimension-7 operator Wilson coefficients, as well as different methods to compute the nuclear matrix elements, is discussed. This work has been submitted to the arxiv:1708.09390.
Relevant References:
arXiv:1708.09390
Journal of High Energy Physics (2017)99
Physics Letters B769 (2017) 460
MeV Axions and New Physics at the GeV Scale
Daniele S. M. Alves recently joined the LANL HEP theory group and has been investigating the possibility of realizing the PQ mechanism (which offers a solution to the Strong CP Problem) at the GeV scale. Several interesting phenomenological consequences include an axion in the several MeV mass range, as well as new GeV states coupled hadronically, a possibility that has been under-explored in BSM physics. Her first paper on this subject (in collaboration with N. Weiner from NYU) was recently posted on the arXiv (arXiv:1710.03764) and submitted for publication. She is working on several follow-ups to this work.
Relevant References:
arXiv:1710.03764