Physics Commons^™

Study Of The Reactions E+E−→2(ΠEΠ−)Π0Π0Π0 And 2(Π+Π−)Π0Π0Η At Center-Of-Mass Energies From Threshold To 4.5 Gev Using Initial-State Radiation, J. P. Lees, V. Poireau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu. G. Kolomensky, M. Fritsch, H. Koch, T. Schroeder, R. Cheaib, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, Milind Purohit, Et. Al.

Faculty Publications

We study the processes e⁺e⁻→2(π⁺π⁻)π⁰π⁰π⁰γ and 2(π⁺π⁻)π⁰π⁰ηγ in which an energetic photon is radiated from the initial state. The data were collected with the BABAR detector at SLAC. About 14 000 and 4700 events, respectively, are selected from a data sample corresponding to an integrated luminosity of 469  fb⁻¹.The invariant mass of the hadronic final state defines the effective e⁺e⁻ center-of-mass energy. The center-of-mass energies range from threshold to 4.5 GeV. From …

On-Shell Representations Of Two-Body Transition Amplitudes: Single External Current, Raúl A. Briceño, Andrew W. Jackura, Felipe G. Ortega-Gama, Keegan H. Sherman

Physics Faculty Publications

This work explores scattering amplitudes that couple two-particle systems via a single external current insertion, 2 + J → 2. Such amplitudes can provide structural information about the excited QCD spectrum. We derive an exact analytic representation for these reactions. From these amplitudes, we show how to rigorously define resonance and bound-state form factors. Furthermore, we explore the consequences of the narrow-width limit of the amplitudes as well as the role of the Ward-Takahashi identity for conserved vector currents. These results hold for any number of two-body channels with no intrinsic spin, and a current with arbitrary Lorentz structure and …

Simultaneous Monte Carlo Analysis Of Parton Densities And Fragmentation Functions, Eric Moffat, W. Melnitchouk, Ted C. Rogers, N. Sato, Jefferson Lab Angular Momentum Collaboration

Physics Faculty Publications

We perform a comprehensive new Monte Carlo analysis of high-energy lepton-lepton, lepton-hadron and hadron-hadron scattering data to simultaneously determine parton distribution functions (PDFs) in the proton and parton to hadron fragmentation functions (FFs). The analysis includes all available semi-inclusive deep-inelastic scattering and single-inclusive e⁺e⁻ annihilation data for pions, kaons and unidentified charged hadrons, which allows the flavor dependence of the fragmentation functions to be constrained. Employing a new multistep fitting strategy and more flexible parametrizations for both PDFs and FFs, we assess the impact of different datasets on sea quark densities and confirm the previously observed suppression …

Intrinsic Transverse Momentum And Evolution In Weighted Spin Asymmetries, Jian-Wei Qiu, Ted C. Rogers, Bowen Wang

Physics Faculty Publications

The transverse momentum-dependent (TMD) and collinear higher twist theoretical factorization frameworks are the most frequently used approaches to describe spin-dependent hard cross sections weighted by and integrated over transverse momentum. Of particular interest is the contribution from small transverse momentum associated with the target bound state. In phenomenological applications, this contribution is often investigated using transverse momentum weighted integrals that sharply regulate the large transverse momentum contribution, for example, with Gaussian parametrizations. Since the result is a kind of hybrid of TMD and collinear (inclusive) treatments, it is important to establish if and how the formalisms are related in applications …

Extraction Of Beam-Spin Asymmetries From The Hard Exclusive Π⁺ Channel Off Protons In A Wide Range Of Kinematics, M.J. Amaryan, D. Bulumulla, M. Hattawy, M. Khachatryan, S.E. Kuhn, Z. W. Zhao, Et Al., The Clas Collaboration

Physics Faculty Publications

We have measured beam-spin asymmetries to extract the sinϕ moment A_LU^sinϕ from the hard exclusive e^→p → e'nπ⁺ reaction above the resonance region, for the first time with nearly full coverage from forward to backward angles in the center of mass. The A_LU^sinϕ moment has been measured up to 6.6  GeV² in -t, covering the kinematic regimes of generalized parton distributions (GPD) and baryon-to-meson transition distribution amplitudes (TDA) at the same time. The experimental results in very forward kinematics demonstrate the sensitivity to chiral-odd and chiral-even GPDs. In very backward kinematics where …

Double Inclusive Small-X Gluon Production And Their Azimuthal Correlations In A Biased Ensemble, Gary Kapilevich

Publications and Research

We consider double gg → g production in the presence of a bias on the unintegrated gluon distribution of the colliding hadrons or nuclei. Such bias could be due to the selection of configurations with a greater number of gluons or higher mean transverse momentum squared or, more generally, due to a modified spectral shape of the gluon distribution in the hadrons. Hence, we consider reweighted functional averages over the stochastic ensemble of small-x gluons. We evaluate explicitly the double inclusive gluon transverse momentum spectrum in high-energy collisions, and their azimuthal correlations, for a few simple examples of biases.

Comeback Measurement Of The Ckm Matrix Element |VCb| From B0 → D*- At Belle, E. Waheed, P. Urquijo, D. Ferlewicz, I. Adachi, K. Adamczyk, H. Aihara, S. Al Said, D.M. Asner, H. Atmacan, T. Aushev, R. Ayad, V. Babu, I. Badhrees, P. Behera, C. Beleño, F. Bernlochner, B. Bhuyan, T. Bilka, J. Biswal, A. Bobrov, Milind Purohit, Et. Al.

Faculty Publications

We present a new measurement of the Cabibbo-Kobayashi-Maskawa matrix element |Vcb| from B⁰ → D^*-ℓ _vℓ decays, reconstructed with the full Belle data set of 711 fb⁻¹ integrated luminosity. Two form factor parametrizations, originally conceived by the Caprini-Lellouch-Neubert (CLN) and the Boyd, Grinstein and Lebed (BGL) groups, are used to extract the product F(1)η_EW||V_cb| and the decay form factors, where F(1) is the normalization factor and η_EW is a small electroweak correction. In the CLN parametrization we find F(1)η_EW||Vcb|=(35.06 ± 0.15 ± 0.56) × 10⁻³, …

Extraction Of Form Factors From A Four-Dimensional Angular Analysis B̅ →D∗ℓ−V̅ ℓ, J. P. Lees, V. Poireau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu G. Kolomensky, M. Fritsch, H. Koch, T. Schroeder, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, V. P. Druzhinin, Milind Purohit, Et. Al.

Faculty Publications

An angular analysis of the decay B̅ → D ∗ ℓ − v̅ ℓ , ℓ ∈ { e , μ } , is reported using the full e ⁺e⁻ collision data set collected by the BABAR experiment at the Υ (4S) resonance. One B meson from the Υ (4S) → B B̅ decay is fully reconstructed in a hadronic decay mode, which constrains the kinematics and provides a determination of the neutrino momentum vector. The kinematics of the semileptonic decay is described by the dilepton mass squared, q² , and three …

Study Of The Reactions E+E-→Π+Π-Π0Π0Π0 And Π+Π-Π0Π0Η At Center-Of-Mass Energies From Threshold To 4.35 Gev Using Initial-State Radiation, J. P. Lees, V. Poireau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu G. Kolomensky, M. Fritsch, H. Koch, T. Schroeder, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, V. P. Druzhinin, V. B. Golubev, E. A. Kozyrev, Milind Purohit, Et. Al.

Faculty Publications

We study the processes e⁺e⁻ → π⁺π⁻π⁰π⁰π⁰nγ in which an energetic photon is radiated from the initial state. The data are collected with the BABAR detector at SLAC. About 14 000 and 4700 events, respectively, are selected from a data sample corresponding to an integrated luminosity of 469 fb⁻¹. The invariant mass of the hadronic final state defines the effective e⁺e⁻ center-of-mass energy. From the mass spectra, the first precise measurement of the e⁺e⁻ → π⁺π^{− …}

First Observation Of P-Odd Γ Asymmetry In Polarized Neutron Capture On Hydrogen, D. Blyth, J. Fry, N. Fomin, R. Alarcon, L. Alonzi, E. Askanazi, S. Baeßler, S. Balascuta, L. Barrón-Palos, A. Barzilov, J. D. Bowman, N. Birge, J. R. Calarco, T. E. Chupp, V. Cianciolo, C. E. Coppola, Chrisopher B. Crawford, K. Craycraft, D. Evans, C. Fieseler, E. Frlež, I. Garishvili, M. T. W. Gericke, R. C. Gillis, K. B. Grammer, G. L. Greene, J. Hall, J. Hamblen, C. Hayes, E. B. Iverson, Md Latiful Kabir, Mark Mccrea, R. Milburn, F. Simmons, Aaron P. Sprow, E. Tang

Physics and Astronomy Faculty Publications

We report the first observation of the parity-violating gamma-ray asymmetry A^np_γ in neutron-proton capture using polarized cold neutrons incident on a liquid parahydrogen target at the Spallation Neutron Source at Oak Ridge National Laboratory. A^np_γ isolates the ΔI = 1, ³S₁ → ³P₁ component of the weak nucleon-nucleon interaction, which is dominated by pion exchange and can be directly related to a single coupling constant in either the DDH meson exchange model or pionless effective field theory. We measured A^np_γ = [−3.0 ± 1.4(stat )± 0.2(syst)] × 10^{−8 …}

Measurement Of The Γ*Γ* → Η' Transition Form Factor, J.P. Lees, V. Poireau, V. Tisserand, E. Grauges, A. Palano, G. Eigen, D. N. Brown, Yu G. Kolomensky, M. Fritsch, H. Koch, T. Schroeder, C. Hearty, T. S. Mattison, J. A. Mckenna, R. Y. So, V. E. Blinov, A. R. Buzykaev, V. P. Druzhinin, V. B. Golubev, Milind Purohit, Et. Al.

Faculty Publications

We study the process e⁺e⁻→e⁺e⁻η′ in the double-tag mode and measure for the first time the γ^*γ^*→ η′ transition form factor Fη′ (Q ² ₁ , Q² ₂) in the momentum-transfer range 2< Q ² ₁ , Q² ₂ 60 GeV ² . The analysis is based on a data sample corresponding to an integrated luminosity of around 469     fb^{− 1} collected at the PEP-II e ⁺e ⁻ collider with the BABAR detector at center-of-mass energies near 10.6 GeV.

1; Q2 2Þ in the …

Measurement Of Unpolarized And Polarized Cross Sections For Deeply Virtual Compton Scattering On The Proton At Jefferson Laboratory With Clas, N. Hirlinger Saylor, B. Guegan, V. D. Burkert, L. Elouadrhiri, M. Garçon, F. X. Girod, M. Guidal, H. S. Jo, V. Kubarovsky, S. Niccolai, P. Stoler, K. P. Adhikari, S. Adhikari, Z. Akbar, M. J. Amaryan, S. Anefalos Pereira, J. Ball, I. Balossino, N. A. Baltzell, L. Barion, M. Battaglieri, V. Batourine, I. Bedlinskiy, A. S. Biselli, S. Boiarinov, W. J. Briscoe, W. K. Brooks, S. Bültmann, F. Cao, S. Carman, Wesley P. Gohn

Physics and Astronomy Faculty Publications

This paper reports the measurement of polarized and unpolarized cross sections for the ep → e′ p′ γ reaction, which is composed of deeply virtual Compton scattering (DVCS) and Bethe-Heitler (BH) processes, at an electron beam energy of 5.88 GeV at the Thomas Jefferson National Accelerator Facility using the Large Acceptance Spectrometer CLAS. The unpolarized cross sections and polarized cross section differences have been measured over broad kinematics, 0.10 < x_B < 0.58, 1.0 < Q² < 4.8GeV², and 0.09 < −t < 2.00GeV². The results are found to be consistent with previous CLAS data, and these new data are discussed in …

Exclusive Photoproduction Of Π0 Up To Large Values Of Mandlestam Variables S, T, And U With Clas, M. C. Kunkel, M. J. Amaryan, I. I. Strakovsky, J. Ritman, G. R. Goldstein, K. P. Adhikari, S. Adhikari, H. Avakian, J. Ball, I. Balossino, L. Barion, M. Battaglieri, V. Batourine, I. Bedlinskiy, A. S. Biselli, S. Boiarinov, W. J. Briscoe, W. K. Brooks, S. Bültmann, V. D. Burkert, F. Cao, D. S. Carman, A. Celentano, G. Charles, T. Chetry, G. Ciullo, L. Clark, P. L. Cole, M. Contalbrigo, O. Cortes, Wesley P. Gohn

Physics and Astronomy Faculty Publications

Exclusive photoproduction cross sections have been measured for the process γp → pπ⁰[e⁺e⁻(γ)] with the Dalitz decay final state using tagged photon energies in the range of E_γ = 1.275–5.425 GeV. The complete angular distribution of the final state π⁰, for the entire photon energy range up to large values of t and u, has been measured for the first time. The data obtained show that the cross section dσ/dt, at mid to large angles, decreases with energy as s^{−6.89±0.26}. This is …

Measurement Of The 3ΛH Lifetime In Au+Au Collisions At The Bnl Relativistic Heavy Ion Collider, L. Adamczyk, J. R. Adams, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, J. Alford, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, K. Barish, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. Bouchet, Renee H. Fatemi, Suvarna Ramachandran

Physics and Astronomy Faculty Publications

An improved measurement of the ³_ΛH lifetime is presented. In this paper, the mesonic decay modes ³_ΛH → ³He + π⁻ and ³_ΛH → d + p + π⁻ are used to reconstruct the ³_ΛH from Au+Au collision data collected by the STAR collaboration at Relativistic Heavy Ion Collider (RHIC). A minimum χ² estimation is used to determine the lifetime of τ = 142⁺²⁴₋₂₁(stat.) ± 29(syst.) ps. This lifetime is about 50% shorter than the lifetime τ = 263 ± 2 ps of a free …

Phenomenology Of Neutron-Antineutron Conversion, Susan Gardner, Xinshuai Yan

Physics and Astronomy Faculty Publications

We consider the possibility of neutron-antineutron (n−n¯) conversion, in which the change of a neutron into an antineutron is mediated by an external source, as can occur in a scattering process. We develop the connections between n−n¯ conversion and n−n¯ oscillation, in which a neutron spontaneously transforms into an antineutron, noting that if n−n¯ oscillation occurs in a theory with baryon number minus lepton number (B-L) violation, then n−n¯ conversion can occur also. We show how an experimental limit on n−n¯ …

Study Of K 0 S Pair Production In Single-Tag Two-Photon Collisions, M. Masuda Et Al., Ratnappuli L. Kulasiri

Faculty and Research Publications

We report a measurement of the cross section for K0S pair production in single-tag two-photon collisions, γ∗γ→K0SK0S, for Q2 up to 30  GeV2, where Q2 is the negative of the invariant mass squared of the tagged photon. The measurement covers the kinematic range 1.0  GeV

Azimuthal Transverse Single-Spin Asymmetries Of Inclusive Jets And Charged Pions Within Jets From Polarized-Proton Collisions At √S = 500 Gev, L. Adamczyk, J. R. Adams, James K. Adkins, G. Agakishiev, M. M. Aggarwal, Z. Ahammed, N. N. Ajitanand, I. Alekseev, D. M. Anderson, R. Aoyama, A. Aparin, D. Arkhipkin, E. C. Aschenauer, M. U. Ashraf, A. Attri, G. S. Averichev, X. Bai, V. Bairathi, K. Barish, A. Behera, R. Bellwied, A. Bhasin, A. K. Bhati, P. Bhattarai, J. Bielcik, J. Bielcikova, L. C. Bland, I. G. Bordyuzhin, J. Bouchet, J. D. Brandenburg, Renee H. Fatemi, Suvarna Ramachandran

Physics and Astronomy Faculty Publications

We report the first measurements of transverse single-spin asymmetries for inclusive jet and jet + π^± production at midrapidity from transversely polarized proton-proton collisions at √s = 500  GeV. The data were collected in 2011 with the STAR detector sampled from 23  pb⁻¹ integrated luminosity with an average beam polarization of 53%. Asymmetries are reported for jets with transverse momenta 6 < p_T < 55  GeV/c and pseudorapidity |η| < 1. Presented are measurements of the inclusive-jet azimuthal transverse single-spin asymmetry, sensitive to twist-3 initial-state quark-gluon correlators; the Collins asymmetry, sensitive to quark transversity coupled to the polarized Collins fragmentation function; and the first measurement of the “Collins-like” asymmetry, sensitive to linearly polarized gluons. Within the present statistical precision, inclusive-jet and Collins-like asymmetries are small, with the latter allowing the first experimental constraints on gluon linear polarization in a polarized proton. At higher values of jet transverse momenta, we observe the first nonzero Collins asymmetries in polarized-proton collisions, with a statistical significance of greater than 5σ. The results span a range of x similar to results from semi-inclusive deep-inelastic scattering but at much higher Q². The Collins results enable tests of …

Search For C P Violation In The D + → Π + Π 0 Decay At Belle, V. Babu Et Al., D. Joffe, Ratnappuli L. Kulasiri

Faculty and Research Publications

We search for CP violation in the charged charm meson decay D+→π+π0, based on a data sample corresponding to an integrated luminosity of 921 fb−1 collected by the Belle experiment at the KEKB e+e− asymmetric-energy collider. The measured CP-violating asymmetry is [+2.31±1.24(stat)±0.23(syst)]%, which is consistent with the standard model prediction and has a significantly improved precision compared to previous results.

Angular Analysis Of The E + E − → Dðþd∓ Process Near The Open Charm Threshold Using Initial-State Radiation, V. Zhukova Et Al., Ratnappuli L. Kulasiri

Faculty and Research Publications

We report a new measurement of the exclusive e+e−→D(*)±D*∓ cross sections as a function of the center-of-mass energy from the D(*)±D*∓ threshold through √s=6.0  GeV, using the initial-state radiation technique. The analysis is based on a data sample collected with the Belle detector with an integrated luminosity of 951  fb−1. The accuracy of the cross section measurement is increased by a factor of 2 over the first Belle study. We perform the first angular analysis of the e+e−→D*±D*∓process and decompose this exclusive cross section into three components corresponding to the D∗helicities.