cern.ch

Updated search for long-lived particles decaying to jet pairs

[to restricted-access page]

Abstract

A search is presented for long-lived particles with a mass between 25 and 50 GeV/$c^2$ and a lifetime between 2 and 500 ps, using proton-proton collision data corresponding to an integrated luminosity of 2.0 fb$^{-1}$, collected by the LHCb detector at centre-of-mass energies of 7 and 8 TeV. The particles are assumed to be pair-produced in the decay of a 125 GeV/$c^2$ Standard-Model-like Higgs boson. The experimental signature is a single long-lived particle, identified by a displaced vertex with two associated jets. No excess above background is observed and limits are set on the production cross-section as a function of the mass and lifetime of the long-lived particle.

Figures and captions

Dijet invariant mass distribution in the different $ R_{xy}$ {} bins, for the 2011 data sample. For illustration, the best fit with a signal $\pi_{\text{v}}$ {} model with mass \SI{35}{\GeVcc} and lifetime \SI{10}{\pico\second} is overlaid. The solid blue line indicates the total background model, the short-dashed green line indicates the signal model for signal strength $\mu=1$, and the long-dashed red line indicates the best-fit signal strength.

Fig1a.pdf [35 KiB]
HiDef png [294 KiB]
Thumbnail [99 KiB]
*.C file
Fig1a.pdf
Fig1b.pdf [35 KiB]
HiDef png [294 KiB]
Thumbnail [98 KiB] *.C file
Fig1b.pdf
Fig1c.pdf [35 KiB]
HiDef png [290 KiB]
Thumbnail [97 KiB] *.C file
Fig1c.pdf
Fig1d.pdf [35 KiB]
HiDef png [304 KiB]
Thumbnail [101 KiB] *.C file
Fig1d.pdf
Fig1e.pdf [35 KiB]
HiDef png [299 KiB]
Thumbnail [99 KiB] *.C file
Fig1e.pdf
Fig1f.pdf [35 KiB]
HiDef png [274 KiB]
Thumbnail [93 KiB] *.C file
Fig1f.pdf

Dijet invariant mass distribution in the different $ R_{xy}$ {} bins, for the 2012 data sample. For illustration, the best fit with a signal $\pi_{\text{v}}$ {} model with mass \SI{35}{\GeVcc} and lifetime \SI{10}{\pico\second} is overlaid. The solid blue line indicates the total background model, the short-dashed green line indicates the signal model for signal strength $\mu=1$, and the long-dashed red line indicates the best-fit signal strength.

Fig2a.pdf [35 KiB]
HiDef png [299 KiB]
Thumbnail [101 KiB]
*.C file
Fig2a.pdf
Fig2b.pdf [35 KiB]
HiDef png [302 KiB]
Thumbnail [99 KiB] *.C file
Fig2b.pdf
Fig2c.pdf [35 KiB]
HiDef png [303 KiB]
Thumbnail [101 KiB] *.C file
Fig2c.pdf
Fig2d.pdf [35 KiB]
HiDef png [309 KiB]
Thumbnail [101 KiB] *.C file
Fig2d.pdf
Fig2e.pdf [36 KiB]
HiDef png [316 KiB]
Thumbnail [103 KiB] *.C file
Fig2e.pdf
Fig2f.pdf [35 KiB]
HiDef png [296 KiB]
Thumbnail [97 KiB] *.C file
Fig2f.pdf

Expected (open circles and dotted line) and observed (filled circles and solid line) upper limit versus lifetime for different $\pi_{\text{v}}$ {} masses and decay modes. The green (dark) and yellow (light) bands indicate the quantiles of the expected upper limit corresponding to \(\pm 1\sigma\) and \(\pm 2\sigma\) for a Gaussian distribution. The decay $\pi_{\text{v}}{}\!\rightarrow b\overline b{}$ is assumed, unless specified otherwise.

Fig3a.pdf [33 KiB]
HiDef png [299 KiB]
Thumbnail [94 KiB]
*.C file
Fig3a.pdf
Fig3b.pdf [33 KiB]
HiDef png [304 KiB]
Thumbnail [93 KiB] *.C file
Fig3b.pdf
Fig3c.pdf [32 KiB]
HiDef png [302 KiB]
Thumbnail [92 KiB] *.C file
Fig3c.pdf
Fig3d.pdf [33 KiB]
HiDef png [296 KiB]
Thumbnail [90 KiB] *.C file
Fig3d.pdf
Fig3e.pdf [33 KiB]
HiDef png [313 KiB]
Thumbnail [96 KiB] *.C file
Fig3e.pdf
Fig3f.pdf [33 KiB]
HiDef png [306 KiB]
Thumbnail [95 KiB] *.C file
Fig3f.pdf

Observed upper limit versus lifetime for different $\pi_{\text{v}}$ {} masses and decay modes. The decay $\pi_{\text{v}}{}\!\rightarrow b\overline b{}$ is assumed, unless specified otherwise.

Fig4.pdf [34 KiB]
HiDef png [233 KiB]
Thumbnail [65 KiB]
*.C file
Fig4.pdf

Animated gif made out of all figures.

PAPER-2016-065.gif
Thumbnail
thumbnail_PAPER-2016-065.gif

Supplementary Material [file]

Fig1b-S.pdf [33 KiB]
HiDef png [323 KiB]
Thumbnail [99 KiB]
*C file
Fig1b-S.pdf
Fig3-S.pdf [308 KiB]
HiDef png [120 KiB]
Thumbnail [56 KiB]
*C file
Fig3-S.pdf
Fig2-S.pdf [22 KiB]
HiDef png [185 KiB]
Thumbnail [49 KiB]
*C file
Fig2-S.pdf
Fig1a-S.pdf [33 KiB]
HiDef png [324 KiB]
Thumbnail [97 KiB]
*C file
Fig1a-S.pdf
Fig1c-S.pdf [33 KiB]
HiDef png [318 KiB]
Thumbnail [98 KiB]
*C file
Fig1c-S.pdf
Fig1d-S.pdf [33 KiB]
HiDef png [312 KiB]
Thumbnail [96 KiB]
*C file
Fig1d-S.pdf
Fig1e-S.pdf [33 KiB]
HiDef png [328 KiB]
Thumbnail [98 KiB]
*C file
Fig1e-S.pdf
LHCb-P[..].pdf [625 KiB]
HiDef png [592 KiB]
Thumbnail [149 KiB]
*C file
LHCb-PAPER-2016-065-supplementary.pdf
Fig1f-S.pdf [33 KiB]
HiDef png [318 KiB]
Thumbnail [97 KiB]
*C file
Fig1f-S.pdf

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