Evidence for the rare decay $\Sigma^+ \to p \mu^+ \mu^-$

Information

LHCb-PAPER-2017-049
CERN-EP-2017-319
arXiv:1712.08606 [PDF]

(Submitted on 22 Dec 2017)
Phys. Rev. Lett. 120 (2018) 221803
Inspire 1644790

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Abstract

A search for the rare decay $\Sigma^+ \to p \mu^+ \mu^-$ is performed using $pp$ collision data recorded by the LHCb experiment at centre-of-mass energies $\sqrt{s} = 7$ and $8$ TeV, corresponding to an integrated luminosity of $3 fb^{-1}$. An excess of events is observed with respect to the background expectation, with a signal significance of 4.1 standard deviations. No significant structure is observed in the dimuon invariant mass distribution, in contrast with a previous result from the HyperCP experiment. The measured $\Sigma^+ \to p \mu^+ \mu^-$ branching fraction is $(2.2 ^{+ 1.8}_{- 1.3})\times 10^{-8}$, where statistical and systematic uncertainties are included, which is consistent with the Standard Model prediction.

Figures and captions

Distribution of the corrected mass $m_{\Sigma}^{\text{corr}}$, defined as in the text, for $\Sigma^+ \rightarrow p \pi^0$ candidates superimposed with the fit to data.	Fig1.pdf [31 KiB] HiDef png [254 KiB] Thumbnail [193 KiB] *.C file
Invariant mass distribution of $\Sigma^+ \rightarrow p \mu^+ \mu^-$ candidates in data.	Fig2.pdf [21 KiB] HiDef png [259 KiB] Thumbnail [196 KiB] *.C file
Background-subtracted distribution of the dimuon invariant mass for $\Sigma^+ \rightarrow p \mu^+ \mu^-$ candidates, superimposed with the distribution from the simulated phase-space (PS) model. Uncertainties on data points are calculated as the square root of the sum of squared weights.	Fig3.pdf [17 KiB] HiDef png [154 KiB] Thumbnail [149 KiB] *.C file
Animated gif made out of all figures.	PAPER-2017-049.gif Thumbnail

Tables and captions

Relative systematic uncertainties associated with the normalisation.

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Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [214 KiB]
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