Polarization observables in low-energy antiproton-proton scattering

Zhou, Daren; Timmermans, Robertus

doi:10.1103/physrevc.87.054005

Cited by 8 publications

(17 citation statements)

References 55 publications

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“…To discriminate different models one can use other observables. For example, calculations were made for double-spin observables in pp scattering [4][5][6][7], and the predictions of different optical potentials were indeed different. Unfortunately, the experimental data for these observables are still absent.…”

Section: Introductionmentioning

confidence: 99%

Real and virtualNN¯pair production near the threshold

Дмитриев¹,

Milstein²,

Salnikov³

2016

Phys. Rev. D

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Nucleon-antinucleon optical potential, which explains the experimental data for the processes e + e − → pp and e + e − → pions near the threshold of pp pair production, is suggested. To obtain this potential we have used the available experimental data for pp scattering, pp pair production in e + e − annihilation, and the ratio of electromagnetic form factors of a proton in the timelike region. It turns out that final-state interaction via the optical potential allows one to reproduce the available experimental data with good accuracy. Our results for the cross sections of e + e − → 6π process near the threshold of pp pair production are in agreement with the recent experiments.

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Section: Introductionmentioning

confidence: 99%

Real and virtualNN¯pair production near the threshold

Дмитриев¹,

Milstein²,

Salnikov³

2016

Phys. Rev. D

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“…It depends on the spin-dependent removal of particles. The effective removal cross section in (3) depends on the machine acceptance and consequently so does the achievable beam polarization, as illustrated, e.g., in figure 15 of [24]. The present paper describes the development effort, including a variety of measurements, necessary to prepare the COSY storage ring and the experimental equipment for the spin-filtering experiments [28,31].…”

Section: Introductionmentioning

confidence: 99%

Toward polarized antiprotons: Machine development for spin-filtering experiments

Weidemann¹,

Rathmann²,

Stein³

et al. 2015

Phys. Rev. ST Accel. Beams

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The paper describes the commissioning of the experimental equipment and the machine studies required for the first spin-filtering experiment with protons at a beam kinetic energy of 49.3MeV in COSY. The implementation of a low-β insertion made it possible to achieve beam lifetimes of τb=8000s in the presence of a dense polarized hydrogen storage-cell target of areal density dt=(5.5±0.2)×1013atoms/cm2. The developed techniques can be directly applied to antiproton machines and allow for the determination of the spin-dependent p¯p cross sections via spin filtering

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“…We use the value a np = (0.44 − i 0.96) fm obtained with a chiral potential [38,39] fitted to state-of-the-art N N partial-wave amplitudes [40,41]. The natural size of a np justifies the assignment H 0 = O(4π/m N Λ NN ) and the use of perturbation theory.…”

mentioning

confidence: 99%

Baryon-Number Violation by Two Units and the Deuteron Lifetime

et al. 2019

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We calculate the lifetime of the deuteron with dimension-nine quark operators that violate baryon number by two units. We construct an effective field theory for |∆B| = 2 interactions that give rise to neutron-antineutron (n-n) oscillations and dinucleon decay within a consistent power counting. We calculate the ratio of the deuteron lifetime to the square of the n-n oscillation time up to next-to-leading order. Our result, which is analytical and has a quantified uncertainty, is smaller by a factor ≃ 2.5 than earlier estimates based on nuclear models, which impacts the indirect bound on the n-n oscillation time and future experiments. We discuss how combined measurements of n-n oscillations and deuteron decay can help to identify the sources of baryon-number violation.a Corresponding author, f.oosterhof@rug.nl At the classical level the standard model (SM) has two accidental global U(1) symmetries associated with baryon-number (B) and lepton-number (L) conservation [1][2][3]. At the quantum level only B − L is conserved, while B + L is anomalous. Since it can be expected that all global symmetries are only approximate, it is plausible that beyond-the-SM (BSM) physics violates B, L, and B − L separately. For instance, extending the SM with the only gauge-invariant dimension-five operator leads to violation of L by two units [1][2][3]. Additional B-and L-violating operators appear at the dimension-six level, while the first gauge-invariant operators that violate B by two units (|∆B| = 2) appear at dimension nine [4].The best limits on B-violating interactions come from the observed stability of the proton. The limit on its lifetime translates into a scale Λ |∆B|=1 > ∼ 10 13 TeV for grand unified theories [5]. Such energies are out of reach of colliders. However, models exist wherein B is only violated by two units and the proton is stable [6][7][8]. These interactions lead to the oscillation of neutral baryons into antibaryons, in analogy to strangeness-changing SM interactions that lead to kaon-antikaon oscillations. In particular, a neutron in a beam can oscillate into an antineutron [9] that annihilates with a nucleon in a target, producing several pions with a few hundred MeV of energy [10]. An ILL experiment sets a lower limit on the neutronantineutron (n-n) oscillation time of τ nn > 0.86 × 10 8 s ≃ 2.7 yr (90% C.L.) [11], which converts to a BSM scale Λ |∆B|=2 > ∼ 10 2 TeV, within reach of future colliders. An experiment at the European Spallation Source can improve τ nn by two orders of magnitude [12], probing regions of parameter space relevant for the observed baryon asymmetry of the Universe [13].Apart from "in-vacuum" n-n oscillations, |∆B| = 2 interactions also induce the decay of otherwise stable nuclei. A bound neutron can oscillate inside the nucleus into an antineutron, which then annihilates with another nucleon. Since a neutron and an antineutron have very different potential energies, the typical nuclear lifetime is far greater than τ nn [4]. Alternatively, two nucleons can annihilate directly....

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Polarization observables in low-energy antiproton-proton scattering

Cited by 8 publications

References 55 publications

Real and virtualNN¯pair production near the threshold

Real and virtualNN¯pair production near the threshold

Toward polarized antiprotons: Machine development for spin-filtering experiments

Baryon-Number Violation by Two Units and the Deuteron Lifetime

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