CMS-PAS-FTR-18-033

CMS-PAS-FTR-18-033
Study of the expected sensitivity to the $\mathrm{P_5'}$ parameter in the $\mathrm{B^0 \to K^{*0}}\mu^+\mu^-$ decay at the HL-LHC
CMS Collaboration
December 2018

Abstract: The expected sensitivity to the $\mathrm{P'_5}$ parameter in $\mathrm{B^0}\to {\rm K}^{0}\mu^+\mu^-$ decays from an integrated luminosity of 300 and 3000 fb$^{-1}$ of pp collisions at a center-of-mass energy of 14 TeV at the HL-LHC is presented. Angular observables in the $\mathrm{B^0}\to {\rm K}^{0}\mu^+\mu^-$ decay, such as the $\mathrm{P'_5}$ parameter, are of particular interest as their theoretical predictions are less affected by hadronic uncertainties. With an integrated luminosity of 3000 fb$^{-1}$, the uncertainties on the shape of the $\mathrm{P'_5}$ parameter will improve by up to a factor of 15, depending on the dimuon mass squared region, compared to the published results from 20 fb$^{-1}$ at 8 TeV.
Links: CDS record (PDF) ; inSPIRE record ; CADI line (restricted) ;

Figures	Summary	References	CMS Publications

Figures
png pdf	Figure 1: Left: the ${\rm K^+}\pi ^-\mu ^+\mu ^-$ invariant mass distribution for bin 2 from Run I (black diamonds) and Phase-2 (red circles) simulation. A fit with the sum of two Gaussian functions is superimposed to each distribution. Right: the ${{\mathrm {B}^0}}$ signal width for each $q^2$ bin in the Run I and Phase-2 simulations.
png pdf	Figure 1-a: The ${\rm K^+}\pi ^-\mu ^+\mu ^-$ invariant mass distribution for bin 2 from Run I (black diamonds) and Phase-2 (red circles) simulation. A fit with the sum of two Gaussian functions is superimposed to each distribution.
png pdf	Figure 1-b: The ${{\mathrm {B}^0}}$ signal width for each $q^2$ bin in the Run I and Phase-2 simulations.
png pdf	Figure 2: Projected statistical (hatched regions) and total (open boxes) uncertainties on the ${\mathrm {P'_5}}$ parameter versus $q^2$ in the Phase-2 scenario with an integrated luminosity of 300 fb$^{-1}$. The CMS Run I measurement of ${\mathrm {P'_5}}$ is shown by circles with inner vertical bars representing the statistical uncertainties and outer vertical bars representing the total uncertainties. The vertical shaded regions correspond to the ${{\mathrm {J}/\psi}}$ and $\psi '$ resonances.
png pdf	Figure 3: Projected statistical (hatched regions) and total (open boxes) uncertainties on the ${\mathrm {P'_5}}$ parameter versus $q^2$ in the Phase-2 scenario with an integrated luminosity of 3000 fb$^{-1}$. The CMS Run I measurement of ${\mathrm {P'_5}}$ is shown by circles with inner vertical bars representing the statistical uncertainties and outer vertical bars representing the total uncertainties. The vertical shaded regions correspond to the ${{\mathrm {J}/\psi}}$ and $\psi '$ resonances. The two lower pads represent the statistical (upper pad) and total (lower pad) uncertainties with the finer $q^2$ binning.

Summary

The large amount of data expected from the HL-LHC will allow CMS to investigate rare B physics decay channels and, in particular, precisely measure the $\mathrm{P'_5}$ parameter shape in the $\mathrm{B^0}\to {\rm K}^{*0}\mu^+\mu^-$ mode through an angular analysis. With the large data set of 3000 fb$^{-1}$, corresponding to around 700K fully reconstructed $\mathrm{B^0}\to {\rm K}^{*0}\mu^+\mu^-$ events, the $\mathrm{P'_5}$ uncertainties in the $q^2$ bins are estimated to improve by up to a factor of 15 compared to the CMS measurement from 20 fb$^{-1}$ of 8 TeV data. We also studied the possibility to perform the analysis of the angular observables in narrower $q^2$ bins, as a better determination of the $\mathrm{P'_5}$ parameter shape will allow significant tests for both beyond Standard Model physics and between different Standard Model calculations. The future sensitivity of the $\mathrm{P'_5}$ angular variable has been presented, however it is worth mentioning that, with the foreseen HL-LHC high statistics, CMS will have the capability to perform a full angular analysis of the $\mathrm{B^0}\to {\rm K}^{*0}\mu^+\mu^-$ decay mode.

References
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