M. J. Betancourt
Massachusetts Institute of Technology
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Featured researches published by M. J. Betancourt.
arXiv: Data Analysis, Statistics and Probability | 2012
M. J. Betancourt
Due to its constrained support, the Dirichlet distribution is uniquely suited to many applications. The constraints that make it powerful, however, can also hinder practical implementations, particularly those utilizing Markov Chain Monte Carlo (MCMC) techniques such as Hamiltonian Monte Carlo. I introduce a series of transformations that reshape the canonical Dirichlet distribution into a form more amenable to efficient MCMC algorithms and demonstrate its utility with a few examples.
Physical Review C | 2013
L. Adamczyk; J. K. Adkins; G. Agakishiev; M. M. Aggarwal; Z. Ahammed; I. Alekseev; J. Alford; C. Anson; A. Aparin; D. Arkhipkin; E. C. Aschenauer; G. S. Averichev; J. Balewski; A. Banerjee; Z. Barnovska; Beavis; R. Bellwied; M. J. Betancourt; R. R. Betts; A. Bhasin; A. K. Bhati; P. Bhattarai; H. Bichsel; J. Bielcik; J. Bielcikova; L. C. Bland; I. Bordyuzhin; W. Borowski; J. Bouchet; A. V. Brandin
Measurements of the elliptic flow, upsilon(2), of identified hadrons (pi(+/-), K-+/-, K-s(0), p, (p) over bar, phi, Lambda, (Lambda) over bar, Xi(-), (Xi) over bar (+), Omega(-), (Omega) over bar (+)) in Au + Au collisions at root s(NN) = 7.7, 11.5, 19.6, 27, 39, and 62.4 GeV are presented. The measurements were done at midrapidity using the time-projection chamber and the time-of-flight detectors of the Solenoidal Tracker at RHIC experiment during the beam-energy scan program at Relativistic Heavy Ion Collider. A significant difference in the upsilon(2) values for particles and the corresponding antiparticles was observed at all transverse momenta for the first time. The difference increases with decreasing center-of-mass energy, root s(NN) (or increasing baryon chemical potential, mu(B)), and is larger for the baryons as compared to the mesons. This implies that particles and antiparticles are no longer consistent with the universal number-of-constituent quark (NCQ) scaling of upsilon(2) that was observed at root s(NN) = 200 GeV. However, for the selected group of particles (p(+), K+, K-s(0), p, Lambda, Xi(-), Omega(-)) NCQ scaling at (m(T) - m(0))/n(q) > 0.4 GeV/c(2) is not violated within +/- 10%. The upsilon(2) values for f mesons at 7.7 and 11.5 GeV are approximately two standard deviations from the trend defined by the other hadrons at the highest measured p(T) values.
Physical Review Letters | 2013
L. Adamczyk; J. K. Adkins; G. Agakishiev; M. M. Aggarwal; Z. Ahammed; I. Alekseev; J. Alford; C. Anson; A. Aparin; D. Arkhipkin; E. C. Aschenauer; G. S. Averichev; J. Balewski; A. Banerjee; Z. Barnovska; D. R. Beavis; R. Bellwied; M. J. Betancourt; R. R. Betts; A. Bhasin; A. K. Bhati; Bhattarai; H. Bichsel; J. Bielcik; J. Bielcikova; L. C. Bland; I. Bordyuzhin; W. Borowski; J. Bouchet; A. V. Brandin
Azimuthal angular correlations of charged hadrons with respect to the axis of a reconstructed (trigger) jet in Au+Au and p+p collisions at √[s(NN)]=200 GeV in STAR are presented. The trigger jet population in Au+Au collisions is biased toward jets that have not interacted with the medium, allowing easier matching of jet energies between Au+Au and p+p collisions while enhancing medium effects on the recoil jet. The associated hadron yield of the recoil jet is significantly suppressed at high transverse momentum (pTassoc) and enhanced at low pTassoc in 0%-20% central Au+Au collisions compared to p+p collisions, which is indicative of medium-induced parton energy loss in ultrarelativistic heavy-ion collisions.
arXiv: Nuclear Experiment | 2018
L. Adamczyk; J. K. Adkins; G. Agakishiev; M. M. Aggarwal; Z. Ahammed; I. Alekseev; J. Alford; C. Anson; A. Aparin; D. Arkhipkin; E. C. Aschenauer; G. S. Averichev; J. Balewski; A. Banerjee; Z. Barnovska; Beavis; R. Bellwied; M. J. Betancourt; R. R. Betts; A. Bhasin; A. K. Bhati; Bhattarai; H. Bichsel; J. Bielcik; J. Bielcikova; L. C. Bland; I. Bordyuzhin; W. Borowski; J. Bouchet; A. V. Brandin
APS | 2010
J. Balewski; M. J. Betancourt; R. Corliss; J. P. Hays-Wehle; A. M. Hoffman; C. L. Jones; A. Kocoloski; William Axel Leight; R. Milner; R. Redwine; T. Sakuma; Joseph Patrick Seele; B. Surrow; Gerrit Jan van Nieuwenhuizen; Matthew Walker
Physical Review Letters | 2009
B. I. Abelev; M. M. Aggarwal; Z. Ahammed; B. D. Anderson; D. Arkhipkin; G. S. Averichev; J. Balewski; O. Barannikova; L. S. Barnby; J. Baudot; S. Baumgart; D. R. Beavis; R. Bellwied; F. Benedosso; M. J. Betancourt; R. R. Betts; A. Bhasin; A. K. Bhati; H. Bichsel; J. Bielcik; J. Bielcikova; B. Biritz; L. C. Bland; M. Bombara; B. E. Bonner; M. Botje; J. Bouchet; E. Braidot; A. V. Brandin; E. Bruna
Physical Review Letters | 2014
J. Balewski; M. J. Betancourt; R. Corliss; J. P. Hays-Wehle; William Axel Leight; R. Milner; R. Redwine; T. Sakuma; Joseph Patrick Seele; S.G. Steadman; B. Surrow; Gerrit Jan van Nieuwenhuizen; Matthew Walker
Physical Review Letters | 2013
J. Balewski; M. J. Betancourt; R. Corliss; James Prewitt Hays-Wehle; William Axel Leight; J. R. Stevens; Gerrit Jan van Nieuwenhuizen
Physical Review Letters | 2013
J. Balewski; M. J. Betancourt; R. Corliss; James Prewitt Hays-Wehle; William Axel Leight; J. R. Stevens; Gerrit Jan van Nieuwenhuizen; Matthew Walker
Physical Review Letters | 2013
M. J. Betancourt; J. Balewski; R. Corliss; James Prewitt Hays-Wehle; William Axel Leight; R. Redwine; Joseph Patrick Seele; S.G. Steadman; Gerrit Jan van Nieuwenhuizen