Precision measurement of the neutral pion lifetime

Larin, I.; Zhang, Y.; Gasparian, A.; Gan, L.; Miskimen, R.; Khandaker, M.; Dale, D.; Danagoulian, S.; Pasyuk, E.; H, Gao; Ahmidouch, A.; Ambrozewicz, P.; Baturin, V.; Burkert, Volker; Clinton, E.; Deur, A.; Dolgolenko, A.; Dutta, D.; Fedotov, G.; Feng, J.; Gevorkyan, S. R.; Glamazdin, A.; Guo, L.; Isupov, E. L.; Ito, M. M.; Klein, F. J.; Kowalski, S.; Kubarovsky, A.; Kubarovsky, V.; Lawrence, D.; Lu, H. Y.; L., L.; Matveev, V.; Morrison, B.; Micherdzińska, A.; Nakagawa, I.; Park, K.; Pedroni, R.; Phelps, W.; Protopopescu, D.; Rimal, D.; Romanov, Dmitry; Salgado, C.; Shahinyan, A.; Sober, D. I.; Stepanyan, S.; Tarasov, V. V.; Taylor, S.; Vasiliev, A. N.; Wood, M. H.; Ye, L.; Zihlmann, B.

doi:10.1126/science.aay6641

Cited by 36 publications

(30 citation statements)

References 28 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Figures 4, 5, and 6 show differential cross sections as a function of the pion pair production angle and invariant mass obtained with the presented calculations for lead-208 nucleus and a 5.5 GeV photon beam energy. For numerical calculations, we take the interference angle between the Coulomb and strong mechanisms to be φ = 1 rad, which is close to the value measured for single π 0 production [18]. dΩdM of two neutral pion photoproduction and its components as a function of two pion production angle for lead-208 nucleus, 0.275 GeV pion pair mass, and 5.5 GeV photon beam energy.…”

Section: Neutral Pion Pairs Via the Charge-exchange Reactionmentioning

confidence: 74%

Photoproduction of pion pairs at high energy and small angles

Gevorkyan,

Larin,

Miskimen

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

We explore the photoproduction mechanisms for charged and neutral pion pairs off a heavy nucleus at threshold. We calculate the production of charged pairs in the Coulomb field of the nucleus in the Born approximation using explicit expressions for the differential cross sections and their connection with the total cross section σ(γγ → π + π − ). The production of σ mesons at threshold and their subsequent decay into pions is an important mechanism and is investigated quantitatively in a framework that can be used for both charged and neutral pions. σ mesons can be produced via electromagnetic (photon exchange) or strong (ω exchange) interactions. For neutral pions, another important production mechanism consists of the two-step process where charged pions are produced first and then charge-exchange into two neutral pions. Differential and total cross sections are computed for each production mechanism.

show abstract

Section: Neutral Pion Pairs Via the Charge-exchange Reactionmentioning

confidence: 74%

Photoproduction of pion pairs at high energy and small angles

Gevorkyan,

Larin,

Miskimen

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

show abstract

“…The electromagnetic calorimeter used in the PRad experiment is a hybrid calorimeter (Hy-Cal) consisting of 1156 PWO 4 inner crystal modules augmented by 576 lead glass modules. The HyCal was built for experiments to carry out precision measurements of the neutral pion radiative decay width (Larin et al, 2011(Larin et al, , 2020. For the PRad experiment, it provides a scattering angular coverage for electron-proton scattering from about 0.7 • to 7.5 • , which corresponds to a Q 2 range of 2 × 10 −4 to 0.06 (GeV/c) 2 .…”

Section: Vacuum Chambermentioning

confidence: 99%

The proton charge radius

Gao,

Vanderhaeghen

2021

Preprint

View full text Add to dashboard Cite

Nucleons (protons and neutrons) are the building blocks of atomic nuclei, and are responsible for more than 99% of the visible matter in the universe. Despite decades of efforts in studying its internal structure, there are still a number of puzzles surrounding the proton such as its spin, and charge radius. Accurate knowledge about the proton charge radius is not only essential for understanding how quantum chromodynamics (QCD) works in the non-perturbative region, but also important for bound state quantum electrodynamics (QED) calculations of atomic energy levels. It also has an impact on the Rydberg constant, one of the most precisely measured fundamental constants in nature. This article reviews the latest situation concerning the proton charge radius in light of the new experimental results from both atomic hydrogen spectroscopy and electron scattering measurements, with particular focus on the latter. We also present the related theoretical developments and backgrounds concerning the determination of the proton charge radius using different experimental techniques. We discuss upcoming experiments, and briefly mention the deuteron charge radius puzzle at the end. CONTENTS I. Introduction 1 II. The Proton Charge Radius Puzzle 3 A. Before the millennium 3 B. After the millennium 3 III. Elastic Electron-Proton Scattering 3 A. Introduction to Electron-Proton Scattering and Proton Electromagnetic Form Factors 3 B. Three-dimensional parton distributions 5 C. The nucleon transverse charge densities 7 D. GPDs and quark densities in longitudinal momentum and transverse position in a proton 10 E. Radii of quark distributions in a proton 12 F. Unpolarized electron-proton elastic scattering 16 G. Double-Polarization Elastic Electron-Proton Scattering 17 1. Spin-Dependent Asymmetry from p( e, e )p 17 2. Recoil Proton Polarization from p( e, e p) 18 H. Two-Photon-Exchange Contribution to Electron-Proton Scattering 18 I. Radiative Corrections in Electron Scattering 20 J. The Extraction of the Proton Charge Radius from Proton Electric Form Factor 21 IV. Atomic Hydrogen Spectroscopy 21 V. Modern lepton scattering experiments 24 A. Mainz 2010 24 B. JLab recoil polarization experiment 24 C. Mainz ISR measurements 24 D. The PRad experiment at JLab 25 E. Proton charge radius from modern analyses of proton electric form factor data 29 VI. Modern spectroscopic measurements 31 A. Muonic hydrogen spectroscopic experiments 31 B. Ordinary Hydrogen spectroscopic experiments 33 VII. Ongoing and upcoming experiments 35 A. The MUSE experiment at PSI 35 B. The COMPASS++/AMBER Experiment at CERN 35 C. The PRad-II experiment at Jefferson Lab 36 D. Future electron scattering experiments at Mainz 38 E. The ULQ 2 experiment at Tohoku University 39 VIII. The deuteron charge radius 39 IX. Conclusions 42 X. Acknowledgments 42 References 43

show abstract

“…Furthermore, ν is the photon energy, β π = 1 − m 2 π /ν 2 the pion velocity, t the momentum transfer to the nucleus and θ π the angle the pion makes with respect to the incoming photon momentum. The most recent PrimEx-II experiment at JLab [307] combined with older experimental determinations leads to Γ(π 0 → γγ) = 7.806(052) (105) eV, with the first and the second uncertainty referring to the statistical and systematic one, respectively. This 1.5% determination improved over its predecessor PrimEx-I [308] by almost a factor of 2.…”

Section: Pion Decay Constant From the Primakoff Effectmentioning

confidence: 99%

Expanding Nuclear Physics Horizons with the Gamma Factory

Budker,

Berengut,

Flambaum

et al. 2021

Preprint

View full text Add to dashboard Cite

The Gamma Factory (GF) is an ambitious proposal, currently explored within the CERN Physics Beyond Colliders program, for a source of photons with energies up to ≈ 400 MeV and photon fluxes (up to ≈ 10 17 photons per second) exceeding those of the currently available gamma sources by orders of magnitude. The high-energy (secondary) photons are produced via resonant scattering of the primary laser photons by highly relativistic partially-stripped ions circulating in the accelerator. The secondary photons are emitted in a narrow cone and the energy of the beam can be monochromatized, eventually down to the ≈ 1 ppm level, via collimation, at the expense of the photon flux. This paper surveys the new opportunities that may be afforded by the GF in nuclear physics and related fields. CONTENTS 11.2. Photon Splitting 48 11.3. Photon Scattering 48 12. Nuclear physics with tertiary beams 49 12.1. Tertiary beams at the GF 49 12.2. Polarized electron, positron and muon sources 49 12.3. High-purity neutrino beams 50 12.4. Neutron and radioactive ion sources 50 12.5. Production of monoenergetic fast neutrons 51 12.6. Metrology with keV neutrons 51 13. Nuclear physics opportunities at the SPS 51 14. Speculative ideas and open questions 51 14.1. Applying the Gamma Factory ideas at other facilities 51 14.2. Nuclear waste transmutation 52 14.3. Laser polarization of PSI 52 14.4. Quark-gluon plasma with polarized PSI 52 14.5. Ground-state hyperfine-structure transitions in PSI 52 14.6. Detection of gravitational waves 53 15. Conclusions and optimistic outlook 53 Acknowledgments 53 Appendix 54 A. Survey of existing and forthcoming gamma facilities 54

show abstract

Precision measurement of the neutral pion lifetime

Cited by 36 publications

References 28 publications

Photoproduction of pion pairs at high energy and small angles

Photoproduction of pion pairs at high energy and small angles

The proton charge radius

Expanding Nuclear Physics Horizons with the Gamma Factory

Contact Info

Product

Resources

About