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Prospects for searches for long-lived particles after the LHCb detector upgrades

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Abstract

The LHCb detector is a single-arm forward spectrometer covering the pseudorapidity range $2 < \eta < 5$, initially designed for the study of particles containing $ b $ or $ c $ quarks. As such, it is naturally suited for the search of beyond SM long-lived particles in a range of mass and lifetime not too dissimilar to heavy-flavour hadrons, as it has been demonstrated in several publications. Prospects for these searches in regard of future LHC upgrades, where challenging conditions are foreseen, are presented in this conference note with the goal to serve as an input for the HL-LHC and HE-LHC Yellow Report.

Figures and captions

Projected sensitivities of the search for RPV supersymmetric neutralinos decaying semileptonically \cite{LHCb-PAPER-2016-047} and produced through a Higgs boson exotic decay. The results are extrapolated from Run 1 results (top left), for luminosities of 23 $\text{ fb} ^{-1}$ (top right), 50 $\text{ fb} ^{-1}$ (bottom left) and 300 $\text{ fb} ^{-1}$ (bottom right). The results are presented in terms of the excluded parameter space of the neutralinos for different upper limits at 95% C.L. on the branching fractions of the Higgs boson decay.

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LLP_compare_RPV_OBS.pdf
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LLP_compare_RPV_UP0.pdf
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LLP_compare_RPV_UP.pdf
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LLP_compare_RPV_HL.pdf
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Comparison of projected sensitivities in the search for RPV supersymmetric neutralinos decaying semileptonically \cite{LHCb-PAPER-2016-047} and produced through a Higgs boson exotic decay. The sensitivities are extrapolated from Run 1 results, and the figure compares parameter regions where the branching fraction of the Higgs boson decay to a $\tilde{\chi}^{0}_{1} \tilde{\chi}^{0}_{1}$ pair is constrained to be smaller than 2% (left) and 0.5% (right) at 95% CL.

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LLP_compare_RPV_2_UP_HL.pdf
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LLP_compare_RPV_05_UP_HL.pdf
LLP_co[..].pdf [63 KiB]
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LLP_compare_legend_RPV_same.pdf

Projected sensitivities of the search for HV pions decaying hadronically \cite{LHCb-PAPER-2016-065} and produced through a Higgs boson exotic decay. The results are extrapolated from Run 1 results (top left), for luminosities of 23 $\text{ fb} ^{-1}$ (top right), 50 $\text{ fb} ^{-1}$ (bottom left) and 300 $\text{ fb} ^{-1}$ (bottom right). The results are presented in terms of the excluded parameter space of the HV pions for different upper limits at 95% C.L. on the branching fractions of the Higgs boson decay.

LLP_co[..].pdf [189 KiB]
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LLP_compare_OBS.pdf
LLP_co[..].pdf [190 KiB]
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LLP_compare_UP0.pdf
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LLP_compare_UP.pdf
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LLP_compare_HL.pdf
LLP_co[..].pdf [64 KiB]
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LLP_compare_legend_1.pdf

Comparison of projected sensitivities in the search for HV pions decaying hadronically \cite{LHCb-PAPER-2016-065} and produced through a Higgs boson exotic decay. The sensitivities are extrapolated from Run 1 results, and the figure compares parameter regions where the branching fraction of the Higgs boson decay to a $\pi_v\pi_v$ pair is constrained to be smaller than 20% (left) and 2% (right) at 95% CL.

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LLP_compare_20_UP_HL.pdf
LLP_co[..].pdf [130 KiB]
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LLP_compare_2_UP_HL.pdf
LLP_co[..].pdf [63 KiB]
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LLP_compare_legend_same.pdf

Animated gif made out of all figures.

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Tables and captions

Assumptions for the integrated luminosity used in this document.

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Table_1.pdf

Examples of the acceptance and total efficiencies assumed to detect a $\tilde{\chi}^{0}_{1}$ decaying semileptonically at a $pp$ collision energy of $\sqrt{s}=13$ TeV at the LHCb detector. Background yields at an integrated luminosity of 1.7 $\text{ fb} ^{-1}$ are also presented. Differences in these yields are due to the effect of a multivariate classifier which is trained differently for each mass-lifetime case.

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Background yields assumed for the HV pion analysis at an integrated luminosity of 23 $\text{ fb} ^{-1}$ . The yields are divided in bins of $R_{xy}=\sqrt{x^2+y^2}$, where $x,y$ are the coordinates of the $\pi_v$ particle decay vertex position. Values are extrapolated from Ref. \cite{LHCb-PAPER-2016-065}.

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Examples of the acceptance and total efficiencies assumed to detect a $\pi_v$ particle decaying to a pair of jets at a $pp$ collision energy $\sqrt{s}=14$ TeV at the LHCb detector. The main inefficiencies arise from the requirements to have $\pi_v$ particle in the VELO and to have the decay products in the LHCb acceptance and from the reconstruction of the secondary vertex. More details can be found in Ref. \cite{LHCb-PAPER-2016-065}.

Table_4.pdf [55 KiB]
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Table_4.pdf

Created on 24 August 2019.Citation count from INSPIRE on 24 August 2019.