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30 records · Page 2

A Program in Medium-Energy Nuclear Physics

We report here on the final stages of the Berman grant. The study of the spectrum and properties of the excited states of the nucleon (the N* states) is one of the highest-priority goals of nuclear physics and one of the major programs of Jefferson Lab, especially in Hall B. We have most recently focused our attention on exclusive studies (in both spin and strangeness) of the neutron in the deuteron. Our g13 experiment, “Production of Kaons from the Deuteron with Polarized Photons” [Nadel-Turonski (2006)], was carried out between October 2006 and June 2007. This experiment was done using both linearly and circularly polarized photons, mainly to try to unscramble the multitude of wide and overlapping N* states and to measure their properties by studying in fine detail their decays into strange-particle reaction channels. To this end, one of our students, Edwin Munevar, has analyzed the γn→K + Σ - reaction channel for his Ph.D. topic. The strangeness-production channels constitute the subject of the original GW group’s g13 proposal. But the g13 data set, by virtue of its statistics, polarization, and kinematic coverage, is ideally suited for many other reaction channels as well. Among these is the azimuthal angular asymmetry for deuteron photodisintegration, which was analyzed by another of our students, Nicholas Zachariou, for his Ph.D. topic, with help from Nickolay Ivanov (from the Yerevan Physics Institute in Armenia). This study required a deuterium target and a linearly polarized photon beam.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Hadron production in e + e - annihilation at BABAR, and implication for the muon anomalous magnetic moment

The BABAR collaboration has an extensive program of studying hadronic cross sections in low-energy e + e - collisions, accessible via initial-state radiation. Our measurements allow significant improvements in the precision of the predicted value of the muon anomalous magnetic moment. These improvements are necessary for illuminating the current 3.6 sigma difference between the predicted and the experimental values. We have published results on a number of processes with two to six hadrons in the final state. We report here the results of recent studies with final states that constitute the main contribution to the hadronic cross section in the energy region between 1 and 3 GeV, as e + e - → K + K - , π + π - , and e + e - → 4 hadrons

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Searches for New Physics in CP Violation from BABAR

Results of recent searches for new physics in CP violation in charm decays from the BABAR experiment are presented. These results include a measurement of D 0 - anti D 0 mixing and searches for CP violation in two-body D 0 decays, a search for CP violation in the charm decays D ± → K S 0 K ± and D s ± → K S 0 K ± , K S 0 π ± , and a search for direct CP violation in the singly-Cabibbo suppressed D ± → K + K - π ± decays. These studies are based on the final dataset collected by BABAR at the PEP-II B factory at SLAC in the period 1999-2008. No evidence of CP violation is found in these charm decays. The measured mixing parameter y CP = [0.72 ± 0.18(stat) ± 0.12(syst)]% excludes the no-mixing null hypothesis with a significance of 3.3σ .

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Empirical description of the hadron-hadron and hadron-nucleus interaction at the accelerator energy range

Taking into account several assumptions, a formula is transformed into two expressions for kaon and baryon plus antibaryon production in proton interaction and for pion production in pion interactions. Combining both formulae, expression are obtained for the spectrum of kaons and baryons plus antibaryons produced in the meson interactions. For analysis of the cosmic ray propagation in the atmosphere in actual fact, instead of the formulae for interactions of protons and mesons with protons, formulae appropriate for interactions with air nuclei was used. Using the method outlined among others by Elias et al. (1980) simple corrections were introduced to the derived expressions to account for the fact that the target is an air nucleus.

Kubiak, G.↗

Neutrino production from the solar atmosphere

When the high energy primary cosmic rays enter near the solar surface, they pass through a thick matter but having a low density. If the density and path length satisfy an appropriate condition, the primaries collide with the constituents near the solar sphere (almost protons) and produce pions and kaons, most of which decay into mu plus nu sub mu without successive hadron collisions. Muons also decay into NU sub mu and NU sub e before reaching the Earth. The neutrino flux of which the producer is matter near the solar surface is computed by solving cascade diffusion equations. The calculated differential flux of muon neutrino at 1 TeV is 1 X 10 to the minus 13 power (GeV. cm square centimeters 2.s.ster)(-1) which is rather difficult to be observed in the present apparatuses or DUMAND.

Inazawa, H.↗

Laser measurements of the radiative lifetime of the B state of CN

A turnable dye laser was used to measure the radiative lifetime of the individual rotational levels of the B2 Sigma (+) state of CN. The radiative lifetime of the unperturbed rotational levels is 65.6 plus or minus 1.0 nsec. A longer radiative lifetime of 72 plus or minus 1 nsec is observed for the Kaon prime = 4 level of the B state. The measured values of the perturbed and unperturbed levels support the longer lifetimes for the A2 meson pion state of CN. The quenching cross section of the B2 Sigma state of CN is 41 plus or minus 20 Angstroms squared and is independent of the rotational energy of the B state.

Jackson, W. M.↗

Recent BABAR Results

We present herein the most recent BABAR results on direct CP asymmetry measurements in B → X s γ, on partial branching fraction and CP asymmetry measurements in B → X s ℓ + ℓ - , on a search for B → π/ηℓ + ℓ - decays, on a search for lepton number violation in B + → X - ℓ + ℓ' + modes and a study of B 0 →ωω and B 0 → ωφ decays.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Branching Fraction and CP Asymmetry Measurements in Inclusive B → X s ℓ⁺ℓ⁻ and B → X s γ Decays from BABAR

We present an update on total and partial branching fractions and on CP asymmetries in the semi-inclusive decay B → X s ℓ⁺ℓ - . Further, we summarize our results on branching fractions and CP asymmetries for semi-inclusive and fully-inclusive B → X s γ decays. We present the first result on the CP asymmetry difference of charged and neutral B → X s γ decays yielding the first constraint on the ratio of Wilson coefficients Im(C 8 eff /C 7 eff ).

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Study of ${B}_c^{+}$ meson decays to charmonia plus multihadron final states

Four decay modes of the ${B}_c^{+}$ meson into a J/ψ meson and multiple charged kaons or pions are studied using proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8, and 13 TeV and corresponding to an integrated luminosity of 9 fb -1 . The decay ${B}_c^{+}$ → J/ψK + K - π + π + π - is observed for the first time, and evidence for the ${B}_c^{+}$ → J/ψ4π + 3π - decay is found. The decay ${B}_c^{+}$ → J/ψ3π + 2π - is observed and the previous observation of the ${B}_c^{+}$ → ψ(2S)π + π + π - decay is confirmed using the ψ(2S) → J/ψπ + π - decay mode. Ratios of the branching fractions of these four ${B}_c^{+}$ decay channels are measured.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Finite-volume effects and the electromagnetic contributions to kaon and pion masses

We report on the MILC Collaboration calculation of electromagnetic effects on light pseudoscalar mesons. The simulations employ asqtad staggered dynamical quarks in QCD plus quenched photons, with lattice spacings varying from 0.12 to 0.06 fm. Finite volume corrections for the MILC realization of lattice electrodynamics have been calculated in chiral perturbation theory and applied to the lattice data. These corrections differ from those calculated by Hayakawa and Uno because our treatment of zero modes differs from theirs. Updated results for the corrections to "Dashen's theorem" are presented.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗

Search for Θ+ in KLp→K+n reaction in KLF at JLab

The possibility of the existence of multiquark hadrons made of 4-quarks for mesons and 5-quarks for baryons was predicted by Gell-Mann [Phys. Lett. 8, 214 (1964)]. The renewed interest for the search for exotic pentaquark states was initiated by the paper by Diakonov, Petrov, and Polyakov [Z. Phys. A 359, 305 (1997)]. The 2003 experimental reports on the observation of [Formula: see text] pentaquark with [Formula: see text] quark content created a great excitement and many following experiments have reported its observation [K. H. Hicks, Eur. Phys. J. H 37, 1 (2012)]. After high-statistics experiments at JLab, which did not confirm previous claims by the CLAS collaboration, the community concluded that the [Formula: see text] pentaquark either does not exist at all or has an extremely small cross-section, making it currently unobserved. There were different review papers on this subject, questioning the existence of [Formula: see text] or trying to explain the reasons why reaching a conclusion based on production experiments is challenging [M. Amaryan, Eur. Phys. J. Plus 137, 684 (2022)]. To address the challenge of minimal 3-body final states, a formation experiment with a projectile-kaon beam is proposed. In the following, we discuss how the [Formula: see text] could be observed in the [Formula: see text] reaction in the KLF experiment at JLab [M. Amaryan et al. [KLF Collaboration], arXiv:2008.08215 [nucl-ex]].

Astronomy & Astrophysics↗

Probing the photon polarization in B → K*γ with conversion

We re-examine the possibility to measure the photon polarization in B → K*γ decays, via decays in which the photon subsequently undergoes nuclear conversion to a lepton pair. We obtain compact expressions for the full decay-plus-conversion amplitude. With these results we show that interference between the B → (K* → Kπ)γ decay and the γN → ℓ + ℓ – N conversion permits both the ratio and relative weak phase between the left- and right-handed photon amplitudes to be probed by an angular observable, constructed from the final state dilepton, kaon and pion kinematic configuration. Exploiting this technique will be experimentally challenging. However, we present special kinematic cuts that enhance the statistical power of this technique by an O(1) factor. Furthermore, we verify this effect and extract pertinent angular kinematic distributions with dedicated numerical simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗