First measurement of ${e}^{+}{e}^{\ensuremath{-}}\ensuremath{\rightarrow}p{K}_{S}^{0}\overline{n}{K}^{\ensuremath{-}}+\mathrm{c}.\mathrm{c}.$ above open charm threshold

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First measurement of $e^{+} e^{-} \to p K_{S}^{0} \bar{n} K^{-} + c . c .$ above open charm threshold

M. Ablikim et al. (BESIII Collaboration)

Phys. Rev. D 98, 032014 – Published 28 August 2018

Abstract

The process $e^{+} e^{-} \to p K_{S}^{0} \bar{n} K^{-} + c . c .$ and its intermediate processes are studied for the first time, using data samples collected with the BESIII detector at BEPCII at center-of-mass energies of 3.773, 4.008, 4.226, 4.258, 4.358, 4.416, and 4.600 GeV, with a total integrated luminosity of $7.4 {fb}^{- 1}$ . The Born cross section of $e^{+} e^{-} \to p K_{S}^{0} \bar{n} K^{-} + c . c .$ is measured at each center-of-mass energy, but no significant resonant structure in the measured cross-section line shape between 3.773 and 4.600 GeV is observed. No evident structure is detected in the $p K^{-}$ , $n K_{S}^{0}$ , $p K_{S}^{0}$ , $n K^{+}$ , $p \bar{n}$ , or $K_{S}^{0} K^{-}$ invariant mass distributions except for $Λ (1520)$ . The Born cross sections of $e^{+} e^{-} \to Λ (1520) \bar{n} K_{S}^{0} + c . c .$ and $e^{+} e^{-} \to Λ (1520) \bar{p} K^{+} + c . c .$ are measured, and the 90% confidence level upper limits on the Born cross sections of $e^{+} e^{-} \to Λ (1520) \bar{Λ} (1520)$ are determined at the seven center-of-mass energies. There is an evident difference in line shape and magnitude of the measured cross sections between $e^{+} e^{-} \to Λ (1520) (\to p K^{-}) \bar{n} K_{S}^{0}$ and $e^{+} e^{-} \to p K^{-} \bar{Λ} (1520) (\to \bar{n} K_{S}^{0})$ .

Received 10 July 2018

DOI:https://doi.org/10.1103/PhysRevD.98.032014

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.

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Physics Subject Headings (PhySH)

Exotic mesons Hadrons Hyperons Quarkonia

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Vol. 98, Iss. 3 — 1 August 2018

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Figure 1
Projections of the simultaneous fits to the $M^{rec} (p K_{S}^{0} K^{-})$ spectra and $K_{S}^{0}$ mass sideband events in $e^{+} e^{-} \to p K_{S}^{0} \bar{n} K^{-}$ at c.m. energies of (a) 3.773, (b) 4.008, (c) 4.226, (d) 4.258, (e) 4.358, (f) 4.416, and (g) 4.600 GeV. The dots with uncertainty bars are the signal candidate events in data, and the green-shaded histograms are shown as the normalized $K_{S}^{0}$ mass sideband events in data. The red solid curves show the total fits, the blue dashed lines are the total background components of the fits, and the violet long dashed curves are the fits to $K_{S}^{0}$ mass sideband events.
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Figure 2
Fits to the $p K^{-}$ and $\bar{n} K_{S}^{0}$ invariant mass distributions to determine signal yields for $e^{+} e^{-} \to Λ (1520) \bar{n} K_{S}^{0}$ and $e^{+} e^{-} \to p K^{-} \bar{Λ} (1520)$ , respectively, where (a) and (b) are from the data at the c.m. energy of 3.773 GeV, and (c) and (d) are from the full $X Y Z$ data. Clear $Λ (1520)$ signals are observed. The red solid lines show the global fits, and the blue dashed curves show the total fitted backgrounds with and without $p K^{-} \bar{n} K_{S}^{0}$ final states. The green-shaded histograms are the contributions of the normalized $K_{S}^{0}$ mass sideband events in data.
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Figure 3
Projections of the 2D fits described in the text to the $M (p K^{-})$ and $M (\bar{n} K_{S}^{0})$ distributions, where (a) and (b) are from the data at the c.m. energy of 3.773 GeV, and (c) and (d) are from the full $X Y Z$ data. The blue solid lines show the best fits, the red solid lines show the $e^{+} e^{-} \to Λ (1520) \bar{Λ} (1520)$ signals, the pink dashed lines represent the fitted non-resonant backgrounds, the gray-blue long dot-dashed lines show the contributions from $e^{+} e^{-} \to Λ (1520) \bar{p} K^{+}$ , and the green long dashed lines indicate the contributions from $e^{+} e^{-} \to Λ (1520) \bar{n} K_{S}^{0}$ .
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Figure 4
Invariant mass distributions of (a) $p K_{S}^{0}$ , (b) $\bar{n} K^{-}$ , (c) $p \bar{n}$ and (d) $K_{S}^{0} K^{-}$ . The dots with error bars show the full experimental data, the green shaded histograms are the contributions from the normalized $K_{S}^{0}$ mass sidebands events.
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Figure 5
Distribution of $σ_{B} (e^{+} e^{-} \to p K_{S}^{0} \bar{n} K^{-})$ versus c.m. energy. The dots with error bars, which show the sum in quadrature of the statistical and uncorrelated systematic uncertainties described in Sec. 5, represent data. The dashed line shows the fit result.
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Figure 6
(Distributions of $σ_{B} [e^{+} e^{-} \to Λ (1520) \bar{n} K_{S}^{0}] \times B [Λ (1520) \to p K^{-}]$ , and $σ_{B} [e^{+} e^{-} \to Λ (1520) \bar{p} K^{+}] \times B [Λ (1520) \to n K_{S}^{0}]$ versus c.m. energy. The dots with error bars, which are the combined statistical and uncorrelated systematic uncertainties described in Sec. 5, represent data. The blue and red dashed lines are the fits to the cross sections of $e^{+} e^{-} \to Λ (1520) \bar{n} K_{S}^{0}$ and $e^{+} e^{-} \to Λ (1520) \bar{p} K^{+}$ , respectively.
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Physical Review D

covering particles, fields, gravitation, and cosmology

First measurement of $e^{+} e^{-} \to p K_{S}^{0} \bar{n} K^{-} + c . c .$ above open charm threshold

M. Ablikim et al. (BESIII Collaboration)

Phys. Rev. D 98, 032014 – Published 28 August 2018

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Physical Review D

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First measurement of e+e−→pKS0n¯K−+c.c. above open charm threshold

M. Ablikim et al. (BESIII Collaboration)

Phys. Rev. D 98, 032014 – Published 28 August 2018

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First measurement of $e^{+} e^{-} \to p K_{S}^{0} \bar{n} K^{-} + c . c .$ above open charm threshold