Search for long-lived particles decaying to jet pairs

The paper is available here.

arXiv: 1412.3021 , LHCB-PAPER-2014-062

More detailed informationLHCb-ANA-2014-006


A search is presented for long-lived particles with a mass between 25 and 50 GeV/c2 and a lifetime between 1 and 200 ps in a sample of proton-proton collisions at a centre-of-mass energy of √s = 7 TeV, corresponding to an integrated luminosity of 0.62 fb−1 , collected by the LHCb detector. The particles are assumed to be pair-produced by the decay of a Standard Model-like Higgs boson. The experimental signature of the long-lived particle is a displaced vertex with two associated jets.No excess above the background is observed and limits are set on the production cross-section as a function of the long-lived particle mass and lifetime.


(Note, pdf and eps versions are available under attachments).

Caption Figure
Figure 1: Di-jet (a) invariant mass and (b) pT distributions for data and for hidden valley models with 25, 35 and 50 GeV/c2 πv masses and 10 ps lifetime. For visibility, the simulated signal is scaled to 0.62 fb−1 assuming a Higgs cross-section of 10 nb and branching fractions of 100 % for B(H → πvπ v) and B(πv → bb). Fig1a.pngFig1b.png
Figure 2: Distribution of the distance of the displaced vertex to the interaction region in the transverse plane for data and for a hidden valley model with mπv = 35 GeV/c2 and τπv = 10 ps after the full selection. For visibility, the simulated signal is scaled to 0.62 fb−1 assuming a Higgs cross-section of 10 nb and branching fractions of 100 % for B(H → π vπv) and B(πv → bb). The boundaries of the intervals used in the fit are indicated by the dotted lines. The generated Rxy distribution is approximately exponential with an average of about 2 mm. Fig2.png
Figure 3: Di-jet invariant mass distributions for each of the five Rxy bins, superimposed with the fits for a hidden valley model with mπv = 35 GeV/c2 and τπv = 10 ps. The blue line indicates the result of the total fit to the data. The black short-dashed line is the background-only contribution, and the red long-dashed line is the fitted signal contribution. Fig3.png
Figure 4: Observed 95 % CL cross-section upper limits on a hidden valley model [3] for various πv masses, as a function of πv lifetime, for πv decays into bb unless specified otherwise. The limits for πv decay to uu and dd are expected to be the same as for ss. Fig4.png
-- KatharinaMueller - 2015-01-05
Topic attachments
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Unknown file formateps Fig1a.eps r1 manage 24.8 K 2015-01-05 - 10:31 KatharinaMueller  
PDFpdf Fig1a.pdf r1 manage 24.5 K 2015-01-05 - 10:31 KatharinaMueller  
PNGpng Fig1a.png r1 manage 41.6 K 2015-01-05 - 10:31 KatharinaMueller  
Unknown file formateps Fig1b.eps r1 manage 31.6 K 2015-01-05 - 10:31 KatharinaMueller  
PDFpdf Fig1b.pdf r1 manage 28.8 K 2015-01-05 - 10:31 KatharinaMueller  
PNGpng Fig1b.png r1 manage 47.3 K 2015-01-05 - 10:31 KatharinaMueller  
Unknown file formateps Fig2.eps r1 manage 17.8 K 2015-01-05 - 10:31 KatharinaMueller  
PDFpdf Fig2.pdf r1 manage 20.8 K 2015-01-05 - 10:31 KatharinaMueller  
PNGpng Fig2.png r1 manage 32.2 K 2015-01-05 - 10:31 KatharinaMueller  
Unknown file formateps Fig3.eps r1 manage 391.8 K 2015-01-05 - 10:37 KatharinaMueller  
PDFpdf Fig3.pdf r1 manage 29.2 K 2015-01-05 - 10:37 KatharinaMueller  
PNGpng Fig3.png r1 manage 227.7 K 2015-01-05 - 10:37 KatharinaMueller  
Unknown file formateps Fig4.eps r1 manage 106.5 K 2015-01-05 - 10:38 KatharinaMueller  
PDFpdf Fig4.pdf r1 manage 14.6 K 2015-01-05 - 10:38 KatharinaMueller  
PNGpng Fig4.png r1 manage 106.2 K 2015-01-05 - 10:38 KatharinaMueller  
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