cern.ch

Observation of excited $\Lambda^0_b$ baryons

[to restricted-access page]

Abstract

Using pp collision data corresponding to 1.0 fb-1 integrated luminosity collected by the LHCb detector, two narrow states are observed in the Lambda_b0pi+pi- spectrum with masses 5911.97 +- 0.12(stat) +- 0.02(syst) +- 0.66(Lambda_b0 mass) MeV/c^2 and 5919.77 +- 0.08(stat) +- 0.02(syst) +- 0.66(Lambda_b0 mass) MeV/c^2. The significances of the observations are 5.2 and 10.2 standard deviations, respectively. These states are interpreted as the orbitally-excited Lambda_b0 baryons, Lambda_b*0(5912) and Lambda_b*0(5920).

Figures and captions

Invariant mass spectrum of $\Lambda ^+_ c \pi ^- $ combinations. The points with error bars are the data, and the fitted $\Lambda ^0_ b \!\rightarrow \Lambda ^+_ c \pi ^- $ signal and three background components ( $\Lambda ^0_ b \!\rightarrow \Lambda ^+_ c K ^- $ , partially-reconstructed and random background) are shown with different fill styles.

lb.pdf [25 KiB]
HiDef png [333 KiB]
Thumbnail [107 KiB]
*.C file
lb.pdf

Invariant mass spectrum of (a) $\Lambda ^0_ b \pi ^+\pi ^- $ and (b) $\Lambda ^0_ b \pi ^\pm \pi ^\pm $ combinations. The points with error bars are the data, the solid line is the fit result, the dashed line is the background contribution.

lbstar.pdf [28 KiB]
HiDef png [215 KiB]
Thumbnail [81 KiB]
*.C file
lbstar.pdf
lbstar_bck.pdf [28 KiB]
HiDef png [193 KiB]
Thumbnail [79 KiB] *.C file
lbstar_bck.pdf

Invariant mass of the two pions from $\Lambda _{ b }^{*0}(5920) \rightarrow \Lambda ^0_ b \pi ^+\pi ^- $ decay. The points with the error bars are background-subtracted data, the solid histogram is the result of phase-space decay simulation.

mhh_splot.pdf [11 KiB]
HiDef png [149 KiB]
Thumbnail [67 KiB]
*.C file
mhh_splot.pdf

Animated gif made out of all figures.

PAPER-2012-012.gif
Thumbnail
thumbnail_PAPER-2012-012.gif

Tables and captions

Systematic uncertainties on the mass difference $\Delta M_{\Lambda _{ b }^{*0} }$ between $\Lambda _{ b }^{*0}$ and $\Lambda ^0_ b $ .

Table_1.pdf [61 KiB]
HiDef png [79 KiB]
Thumbnail [11 KiB]
tex code
Table_1.pdf

Created on 09 December 2018.Citation count from INSPIRE on 18 December 2018.