Search for $C P$ violation and observation of $P$ violation in $\Lambda_b^0 \to p \pi^- \pi^+ \pi^-$ decays

Information

LHCb-PAPER-2019-028
CERN-EP-2019-256
arXiv:1912.10741 [PDF]

(Submitted on 23 Dec 2019)
Phys. Rev. D102 (2020) 051101
Inspire 1773072

Tools

Abstract

A search for $C P$ violation in the $\Lambda_b^0 \to p \pi^- \pi^+ \pi^-$ decay is performed using LHCb data corresponding to an integrated luminosity of 6.6$ fb^{-1}$ collected in $pp$ collisions at centre-of-mass energies of 7, 8 and 13$ Te V$. The analysis uses both triple product asymmetries and the unbinned energy test method. The highest significances of $C P$ asymmetry are 2.9 standard deviations from triple product asymmetries and 3.0 standard deviations for the energy test method. Once the global $p$-value is considered, all results are consistent with no $C P$ violation. Parity violation is observed at a significance of $5.5$ standard deviations for the triple product asymmetry method and $5.3$ standard deviations for the energy test method.

Figures and captions

Invariant-mass distribution for $\Lambda ^0_ b \rightarrow p \pi ^- \pi ^+ \pi ^- $ candidates with the result of the fit overlaid. The solid and dotted lines describe the projections of the fit results for various components as listed in the legend.	Lb2p3pi.pdf [38 KiB] HiDef png [321 KiB] Thumbnail [256 KiB] *.C file
Measured asymmetries for the binning scheme (left) $A_1$ and $A_2$ and (right) $B_1$ and $B_2$. The error bars represent the sum in quadrature of the statistical and systematic uncertainties. The $\chi^2$ per ndof is calculated with respect to the null hypothesis and includes statistical and systematic uncertainties.	TPAAsy[..].pdf [22 KiB] HiDef png [331 KiB] Thumbnail [265 KiB] *.C file
	TPAAsy[..].pdf [20 KiB] HiDef png [289 KiB] Thumbnail [246 KiB] *.C file
Animated gif made out of all figures.	PAPER-2019-028.gif Thumbnail

Tables and captions

The $p$-values from the energy test for different distance scales and test configurations.	Table_1.pdf [45 KiB] HiDef png [41 KiB] Thumbnail [19 KiB] tex code
Definition of binning scheme $A$. This binning scheme is based on the helicity angles of the decay topology $\Lambda ^0_ b \rightarrow \left( N^{+} \rightarrow \left(\Delta ^{++} \rightarrow p \pi ^+ \right)\pi ^- \right)\pi ^- $ where $\varphi$ is the azimuthal angle of the proton in the $\Delta^{++}$ rest frame and $\theta_{\Delta ^{++}}$ ($\theta_ p $) is the polar angle of the $\Delta ^{++}$ ($ p $) in the $N^{+}$ ($\Delta ^{++}$) rest frame.	Table_2.pdf [53 KiB] HiDef png [267 KiB] Thumbnail [138 KiB] tex code

Supplementary Material [file]

Supplementary material full pdf	supple[..].pdf [1 MiB]
This ZIP file contains supplemetary material for the publication LHCb-PAPER-2019-028. The files are: Supplementary.pdf : "Search for CP violation and observation of P violation in Lb --> p pi^- pi^+ pi^- decays" Supplementary.tex	Fig3a.pdf [15 KiB] HiDef png [155 KiB] Thumbnail [152 KiB] *C file
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