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The extraction of φ–N total cross section from d(γ,p<sup>K+</sup><sup>K−</sup>)n
Qian, X.,Chen, W.,Gao, H.,Hicks, K.,Kramer, K.,Laget, J.M.,Mibe, T.,Stepanyan, S.,Tedeschi, D.J.,Xu, W.,Adhikari, K.P.,Amaryan, M.,Anghinolfi, M.,Baghdasaryan, H.,Ball, J.,Battaglieri, M.,Batourine, V Elsevier 2009 Physics letters: B Vol.680 No.5
<P><B>Abstract</B></P><P>We report on the first measurement of the differential cross section of <I>φ</I>-meson photoproduction for the d(γ,p<SUP>K+</SUP><SUP>K−</SUP>)n exclusive reaction channel. The experiment was performed using a tagged-photon beam and the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. A combined analysis using data from the d(γ,p<SUP>K+</SUP><SUP>K−</SUP>)n channel and those from a previous publication on coherent <I>φ</I> production on the deuteron has been carried out to extract the φ−N total cross section, <SUB>σφN</SUB>. The extracted φ−N total cross section favors a value above 20 mb. This value is larger than the value extracted using vector-meson dominance models for <I>φ</I> photoproduction on the proton.</P>
Photoproduction of the<sub>f1</sub>(1285)meson
Dickson, R.,Schumacher, R. A.,Adhikari, K. P.,Akbar, Z.,Amaryan, M. J.,Anefalos Pereira, S.,Badui, R. A.,Ball, J.,Battaglieri, M.,Batourine, V.,Bedlinskiy, I.,Biselli, A.,Boiarinov, S.,Briscoe, W. J. American Physical Society 2016 Physical Review C Vol.93 No.6
<P>The f(1)(1285) meson withmass 1281.0 +/- 0.8MeV/c(2) and width 18.4 +/- 1.4MeV (full width at half maximum) was measured for the first time in photoproduction from a proton target using CLAS at Jefferson Lab. Differential cross sections were obtained via the eta pi(+)pi(-), K+(K) over bar (0) pi(-), and (K-K0)pi(+) decay channels from threshold up to a center-of-mass energy of 2.8 GeV. The mass, width, and an amplitude analysis of the eta pi(+)pi(-) final-state Dalitz distribution are consistent with the axial-vector J(P) = 1(+) f(1)(1285) identity, rather than the pseudoscalar 0(-) eta(1295). The production mechanism is more consistent with s-channel decay of a high-mass N* state and not with t-channel meson exchange. Decays to eta pi pi go dominantly via the intermediate a(0)(+/-) (980)pi(-/+) states, with the branching ratio Gamma [a(0)pi (no (K) over barK)]/Gamma[eta pi pi (all)] = 0.74 +/- 0.09. The branching ratios Gamma (K (K) over bar pi)/Gamma(eta pi pi) = 0.216 +/- 0.033 and Gamma (gamma rho(0))/Gamma(eta pi pi) = 0.047 +/- 0.018 were also obtained. The first is in agreement with previous data for the f(1)(1285), while the latter is lower than the world average.</P>
THE RATE OF BINARY BLACK HOLE MERGERS INFERRED FROM ADVANCED LIGO OBSERVATIONS SURROUNDING GW150914
Abbott, B. P.,Abbott, R.,Abbott, T. D.,Abernathy, M. R.,Acernese, F.,Ackley, K.,Adams, C.,Adams, T.,Addesso, P.,Adhikari, R. X.,Adya, V. B.,Affeldt, C.,Agathos, M.,Agatsuma, K.,Aggarwal, N.,Aguiar, O. American Astronomical Society 2016 ASTROPHYSICAL JOURNAL LETTERS - Vol.833 No.1
<P>A transient gravitational-wave signal, GW150914, was identified in the twin Advanced LIGO detectors on 2015 September 2015 at 09: 50: 45 UTC. To assess the implications of this discovery, the detectors remained in operation with unchanged configurations over a period of 39 days around the time of the signal. At the detection statistic threshold corresponding to that observed for GW150914, our search of the 16 days of simultaneous two-detector observational data is estimated to have a false-alarm rate (FAR) of <4.9 x 10(-6) yr(-1), yielding a p-value for GW150914 of <2 x 10(-7). Parameter estimation follow-up on this trigger identifies its source as a binary black hole (BBH) merger with component masses (m(1), m(2)) = (36(-4)(+5), 29(-4)(+4))M-circle dot at redshift z = 0.09(-0.04)(+0.03) (median and 90% credible range). Here, we report on the constraints these observations place on the rate of BBH coalescences. Considering only GW150914, assuming that all BBHs in the universe have the same masses and spins as this event, imposing a search FAR threshold of 1 per 100 years, and assuming that the BBH merger rate is constant in the comoving frame, we infer a 90% credible range of merger rates between 2-53 Gpc(-3) yr(-1)(comoving frame). Incorporating all search triggers that pass a much lower threshold while accounting for the uncertainty in the astrophysical origin of each trigger, we estimate a higher rate, ranging from 13-600 Gpc(-3) yr(-1) depending on assumptions about the BBH mass distribution. All together, our various rate estimates fall in the conservative range 2-600 Gpc(-3) yr(-1).</P>
Photoproduction ofΛand<sup>Σ0</sup>hyperons using linearly polarized photons
Paterson, C. A.,Ireland, D. G.,Livingston, K.,McKinnon, B.,Adhikari, K. P.,Adikaram, D.,Akbar, Z.,Amaryan, M.,Anefalos Pereira, S.,Badui, R. A.,Ball, J.,Baltzell, N. A.,Battaglieri, M.,Bedlinskiy, I. American Physical Society 2016 Physical review. C Vol.93 No.6
<P>Background: Measurements of polarization observables for the reactions (gamma) over right arrowp -> K+ Lambda and (gamma) over right arrowp -> K+ Sigma(0) have been performed. This is part of a program of measurements designed to study the spectrum of baryon resonances in particular, and nonperturbative QCD in general. Purpose: The accurate measurement of several polarization observables provides tight constraints for phenomenological fits, which allow the study of strangeness in nucleon and nuclear systems. Beam-recoil observables for the (gamma) over right arrowp -> K+ Sigma(0) reaction have not been reported before now. Method: Themeasurements were carried out using linearly polarized photon beams incident on a liquid hydrogen target, and the CLAS detector at the Thomas Jefferson National Accelerator Facility. The energy range of the results is 1.71 < W < 2.19 GeV, with an angular range -0.75 < cos theta(K)* < +0.85. Results: The observables extracted for both reactions are beam asymmetry Sigma, target asymmetry T, and the beam-recoil double polarization observables O-x and O-z. Conclusions: Comparison with theoretical fits indicates that, in the regions where no previous data existed, the new data contain significant new information, and strengthen the evidence for the set of resonances used in the latest Bonn-Gatchina fit.</P>
CLAS Collaboration,Pereira, S.A.,Mirazita, M.,Rossi, P.,De Sanctis, E.,Niculescu, G.,Niculescu, I.,Stepanyan, S.,Adhikari, K.P.,Aghasyan, M.,Anghinolfi, M.,Baghdasaryan, H.,Ball, J.,Battaglieri, M.,Be North-Holland Pub. Co 2010 Physics letters: B Vol.688 No.4
<P>Differential cross sections of the reaction gamma d -> K+Sigma(-)(p) have been measured with the CLAS detector at Jefferson Lab using incident photons with energies between 1.1 and 3.6 GeV. This is the first complete set of strangeness photoproduction data on the neutron covering a broad angular range. At energies close to threshold and up to E-gamma similar to 1.8 GeV. the shape of the angular distribution is suggestive of the presence of s-channel production mechanisms. For E-gamma > 1.8 GeV, a clear forward peak appears and becomes more prominent as the photon energy increases, suggesting contributions from t-channel production mechanisms. These data can be used to constrain future analysis of this reaction. (c) 2010 Elsevier B.V. All rights reserved.</P>
GW150914: The Advanced LIGO Detectors in the Era of First Discoveries
Abbott, B. P.,Abbott, R.,Abbott, T. D.,Abernathy, M. R.,Acernese, F.,Ackley, K.,Adams, C.,Adams, T.,Addesso, P.,Adhikari, R. X.,Adya, V. B.,Affeldt, C.,Agathos, M.,Agatsuma, K.,Aggarwal, N.,Aguiar, O. American Physical Society 2016 Physical Review Letters Vol.116 No.13
<P>Following a major upgrade, the two advanced detectors of the Laser Interferometer Gravitational-wave Observatory (LIGO) held their first observation run between September 2015 and January 2016. With a strain sensitivity of 10(-23) / root Hz at 100 Hz, the product of observable volume and measurement time exceeded that of all previous runs within the first 16 days of coincident observation. On September 14, 2015, the Advanced LIGO detectors observed a transient gravitational-wave signal determined to be the coalescence of two black holes [B. P. Abbott et al., Phys. Rev. Lett. 116, 061102 (2016)], launching the era of gravitational-wave astronomy. The event, GW150914, was observed with a combined signal-to-noise ratio of 24 in coincidence by the two detectors. Here, we present the main features of the detectors that enabled this observation. At full sensitivity, the Advanced LIGO detectors are designed to deliver another factor of 3 improvement in the signal-to-noise ratio for binary black hole systems similar in mass to GW150914.</P>
Understanding NaI(Tl) crystal background for dark matter searches
Adhikari, G.,Adhikari, P.,Ha, C.,Jeon, E. J.,Kim, N. Y.,Kim, Y. D.,Kong, S. Y.,Lee, H. S.,Oh, S. Y.,Park, J. S.,Park, K. S. Springer-Verlag 2017 The European physical journal. C, Particles and fi Vol.77 No.7
<P>We have developed ultra-low-background NaI(Tl) crystals to reproduce the DAMA results with the ultimate goal of achieving purity levels that are comparable to or better than those of the DAMA/LIBRA crystals. Even though the achieved background level does not approach that of DAMA/LIBRA, it is crucial to have a quantitative understanding of the backgrounds. We have studied background simulations toward a deeper understanding of the backgrounds and developed background models for a 9.16-kg NaI(Tl) crystal used in the test arrangement. In this paper we describe the contributions of background sources quantitatively by performing Geant4 Monte Carlo simulations that are fitted to the measured data to quantify the unknown fractions of the background compositions. In the fitted results, the overall simulated background spectrum well describes the measured data with a 9.16-kg NaI(Tl) crystal and shows that the background sources are dominated by surface Pb-210 and internal K-40 in the 2-6-keV energy interval, which produce 2.4 counts/day/keV/kg (dru) and 0.5 dru, respectively.</P>
Near-threshold photoproduction of φ mesons from deuterium
CLAS Collaboration,Qian, X.,Chen, W.,Gao, H.,Hicks, K.,Kramer, K.,Laget, J.M.,Mibe, T.,Qiang, Y.,Stepanyan, S.,Tedeschi, D.J.,Xu, W.,Adhikari, K.P.,Amaryan, M.,Anghinolfi, M.,Ball, J.,Battaglieri, M. North-Holland Pub. Co 2011 Physics letters: B Vol.696 No.4
We report the first, kinematically-complete measurement of the differential cross section of φ-meson photoproduction from deuterium near the production threshold for a proton using the CLAS detector and a tagged-photon beam in Hall B at Jefferson Lab. The measurement was carried out by a triple coincidence detection of a proton, K<SUP>+</SUP> and K<SUP>-</SUP> near the theoretical production threshold of 1.57 GeV. The extracted differential cross sections dσdt for the initial photon energy range of 1.65-1.75 GeV are consistent with predictions based on a quasifree mechanism. Our finding is different from recent LEPS results on φ-meson photoproduction from deuterium in a similar incident photon energy range, but in a different momentum transfer region.
Gravitational Waves and Gamma-Rays from a Binary Neutron Star Merger: GW170817 and GRB 170817A
Abbott, B. P.,Abbott, R.,Abbott, T. D.,Acernese, F.,Ackley, K.,Adams, C.,Adams, T.,Addesso, P.,Adhikari, R. X.,Adya, V. B.,Affeldt, C.,Afrough, M.,Agarwal, B.,Agathos, M.,Agatsuma, K.,Aggarwal, N.,Agu American Astronomical Society 2017 ASTROPHYSICAL JOURNAL LETTERS - Vol.848 No.2
<P>On 2017 August 17, the gravitational-wave event GW170817 was observed by the Advanced LIGO and Virgo detectors, and the gamma-ray burst (GRB) GRB. 170817A was observed independently by the Fermi Gamma-ray Burst Monitor, and the Anti-Coincidence Shield for the Spectrometer for the International Gamma-Ray Astrophysics Laboratory. The probability of the near-simultaneous temporal and spatial observation of GRB. 170817A and GW170817 occurring by chance is 5.0 x 10(-8). We therefore confirm binary neutron star mergers as a progenitor of short GRBs. The association of GW170817 and GRB. 170817A provides new insight into fundamental physics and the origin of short GRBs. We use the observed time delay of (+ 1.74 +/- 0.05) s between GRB. 170817A and GW170817 to: (i) constrain the difference between the speed of gravity and the speed of light to be between -3 x 10(-15) and + 7 x 10(-16) times the speed of light, (ii) place new bounds on the violation of Lorentz invariance, (iii) present a new test of the equivalence principle by constraining the Shapiro delay between gravitational and electromagnetic radiation. We also use the time delay to constrain the size and bulk Lorentz factor of the region emitting the gamma-rays. GRB. 170817A is the closest short GRB with a known distance, but is between 2 and 6 orders of magnitude less energetic than other bursts with measured redshift. A new generation of gamma-ray detectors, and subthreshold searches in existing detectors, will be essential to detect similar short bursts at greater distances. Finally, we predict a joint detection rate for the Fermi Gamma-ray Burst Monitor and the Advanced LIGO and Virgo detectors of 0.1-1.4 per year during the 2018-2019 observing run and 0.3-1.7 per year at design sensitivity.</P>
Abadie, J.,Abbott, B. P.,Abbott, R.,Abbott, T. D.,Abernathy, M.,Accadia, T.,Acernese, F.,Adams, C.,Adhikari, R. X.,Affeldt, C.,Agathos, M.,Agatsuma, K.,Ajith, P.,Allen, B.,Ceron, E. Amador,Amariutei, IOP Publishing 2012 The Astrophysical journal Vol.760 No.1
<P>We present the results of a search for gravitational waves associated with 154 gamma-ray bursts (GRBs) that were detected by satellite-based gamma-ray experiments in 2009-2010, during the sixth LIGO science run and the second and third Virgo science runs. We perform two distinct searches: a modeled search for coalescences of either two neutron stars or a neutron star and black hole, and a search for generic, unmodeled gravitational-wave bursts. We find no evidence for gravitational-wave counterparts, either with any individual GRB in this sample or with the population as a whole. For all GRBs we place lower bounds on the distance to the progenitor, under the optimistic assumption of a gravitational-wave emission energy of 10(-2) M-circle dot c(2) at 150 Hz, with a median limit of 17 Mpc. For short-hard GRBs we place exclusion distances on binary neutron star and neutron-star-black-hole progenitors, using astrophysically motivated priors on the source parameters, with median values of 16 Mpc and 28 Mpc, respectively. These distance limits, while significantly larger than for a search that is not aided by GRB satellite observations, are not large enough to expect a coincidence with a GRB. However, projecting these exclusions to the sensitivities of Advanced LIGO and Virgo, which should begin operation in 2015, we find that the detection of gravitational waves associated with GRBs will become quite possible.</P>