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CMS-PAS-BPH-15-008
Measurement of the P1 and P5 angular parameters of the decay B0K0μ+μ in proton-proton collisions at s= 8 TeV
Abstract: The angular distributions of the decay B0K0μ+μ are studied using data corresponding to an integrated luminosity of 20.5 fb1 collected with the CMS detector at the LHC in proton-proton collisions at s= 8 TeV. An angular analysis gives access to many physical observables, including P5, which is of particular interest due to measurements from the LHCb Collaboration, that exibit potential discrepancy with the standard model. Based on a sample of 1397 signal events, the P1 and P5 angular parameters are determined as a function of the dimuon invariant mass squared. The measurement are in agreement with standard model predictions.
Figures & Tables Summary Additional Figures References CMS Publications
Figures

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Figure 1:
Sketch showing the definition of the angular variables θl (left), θK (middle), and ϕ (right) for the decay B0K0(K+π)μ+μ.

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Figure 2:
K+πμ+μ invariant mass and angular distributions for the second and third q2 bin (top four plots) 2.00 <q2< 4.30 GeV2, and (bottom four plots) 4.30 <q2< 6.00 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Figure 2-a:
K+πμ+μ invariant mass and angular distributions for the second q2 bin, 2.00 <q2< 4.30 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Figure 2-b:
K+πμ+μ invariant mass and angular distributions for the third q2 bin, 4.30 <q2< 6.00 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Figure 3:
Measured values of P1 and P5 versus q2 for B0K0μ+μ from CMS, compared with LHCb [30] and Belle [32] results. The statistical uncertainty is shown by the inner vertical bars, while the outer vertical bars give the total uncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspond to the J/ψ and ψ resonances. The red and blue hatched regions show two SM predictions averaging over each q2 bin to provide a direct comparison to the data. The SM-DHMV result is derived from Refs. [17,24], while SM-HEPfit result from Refs. [48,49]. Reliable theoretical predictions are not available near the J/ψ and ψ resonances.

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Figure 3-a:
Measured values of P1 versus q2 for B0K0μ+μ from CMS, compared with LHCb [30] and Belle [32] results. The statistical uncertainty is shown by the inner vertical bars, while the outer vertical bars give the total uncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspond to the J/ψ and ψ resonances. The red and blue hatched regions show two SM predictions averaging over each q2 bin to provide a direct comparison to the data. The SM-DHMV result is derived from Refs. [17,24], while SM-HEPfit result from Refs. [48,49]. Reliable theoretical predictions are not available near the J/ψ and ψ resonances.

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Figure 3-b:
Measured values of P5 versus q2 for B0K0μ+μ from CMS, compared with LHCb [30] and Belle [32] results. The statistical uncertainty is shown by the inner vertical bars, while the outer vertical bars give the total uncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspond to the J/ψ and ψ resonances. The red and blue hatched regions show two SM predictions averaging over each q2 bin to provide a direct comparison to the data. The SM-DHMV result is derived from Refs. [17,24], while SM-HEPfit result from Refs. [48,49]. Reliable theoretical predictions are not available near the J/ψ and ψ resonances.
Tables

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Table 1:
Systematic uncertainty contributions for the measurements of P1 and P5. The total uncertainty in each q2 bin is obtained by adding each contribution in quadrature. For each item, the range indicates the variation of the uncertainty in the q2 bins.

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Table 2:
The measured signal yields, which include both correctly tagged and mistagged events, and the P1 and P5 values, in bins of q2, for the decay B0K0μ+μ. The first uncertainty is statistical and the second is systematic. The bin ranges are selected to allow comparisons to previous measurements.
Summary
Using pp collision data recorded at s= 8 TeV with the CMS detector at the LHC, corresponding to an integrated luminosity of 20.5 fb1, an angular analysis has been performed for the decay B0K0μ+μ. In total, 1397 signal events are obtained. For each bin of the dimuon invariant mass squared (q2), unbinned maximum-likelihood fits were performed to the distributions of the K+πμ+μ invariant mass and the three decay angles, to obtain values of the P1 and P5 parameters. The results are among the most precise to date and are consistent with standard model predictions and previous measurements.
Additional Figures

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Additional Figure 1:
Spectrum of the di-muon invariant mass. The two peaks correspond to the J/ψ and ψ resonances used as control samples.

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Additional Figure 2:
Projection of the efficiency computed on simulated events along the three angular variables cosθK, |cosθL|, ϕ for the second bin 2.00 <q2< 4.30 GeV2 for correctly tagged events.

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Additional Figure 3:
Projection of the efficiency computed on simulated events along the three angular variables cosθK, |cosθL|, ϕ for the seventh bin 16.00 <q2< 19.00 GeV2 for correctly tagged events.

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Additional Figure 4:
Projection of the efficiency computed on simulated events along the three angular variables cosθK, |cosθL|, ϕ for the second bin 2.00 <q2< 4.30 GeV2 for wrongly tagged events.

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Additional Figure 5:
Projection of the efficiency computed on simulated events along the three angular variables cosθK, |cosθL|, ϕ for the seventh bin 16.00 <q2< 19.00 GeV2 for wrongly tagged events.

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Additional Figure 6:
Closure test of efficiency using simulated events for correctly tagged events. Half of the simulated events are used to compute the efficiency, and the other half is used for the test. The black dots are are the simulated events reconstructed, the red histograms are the distribution of the events at generator level, multiplied by the efficiency.

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Additional Figure 7:
Closure test of efficiency using simulated events for wrongly tagged events. Half of the simulated events are used to compute the efficiency, and the other half is used for the test. The black dots are are the simulated events reconstructed, the red histograms are the distribution of the events at generator level, multiplied by the efficiency.

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Additional Figure 8:
Closure test of the fitting results of P5 for each q2 bin on simulated data. The results of the fit on reconstructed events (black dots) are compared with the fit on the generated events (red dots). The vertical shaded regions correspond to the J/ψ and ψ resonances.

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Additional Figure 9:
Closure test of the fitting results of P1 for each q2 bin on simulated data. The results of the fit on reconstructed events (black dots) are compared with the fit on the generated events (red dots). The vertical shaded regions correspond to the J/ψ and ψ resonances.

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Additional Figure 10:
Distribution of L computed on data for third bin 2.00 <q2< 4.30 GeV2, in the P1,P5 plane. The colored regions correspond to ΔlogL< 0.5 (yellow), 0.5 <ΔlogL< 2.0 (green), ΔlogL> 2.0 (purple), respectively. The magenta line represents the physical boundary, the physically allowed region being above that line. Superimposed is a bivariate Gaussian fit (dot-dashed line), and the position of the maxima of the profiled L along P1, with P5 fixed, (blue crosses) and along P5, with P1 fixed, (red crosses).

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Additional Figure 11:
Distribution of L computed on data for third bin 4.30<q2<6.00 GeV2, in the P1,P5 plane. The colored regions correspond to ΔlogL< 0.5 (yellow), 0.5 <ΔlogL< 2.0 (green), ΔlogL> 2.0 (purple), respectively. The magenta line represents the physical boundary, the physically allowed region being above that line. Superimposed is a bivariate Gaussian fit (dot-dashed line), and the position of the maxima of the profiled L along P1, with P5 fixed, (blue crosses) and along P5, with P1 fixed, (red crosses).

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Additional Figure 12:
K+πμ+μ invariant mass and angular distributions of the control channel J/ψ on data. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Additional Figure 13:
K+πμ+μ invariant mass and angular distributions of the control channel ψon data. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Additional Figure 14:
K+πμ+μ invariant mass and angular distributions for the first q2 bin 1.00 <q2< 2.00 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Additional Figure 15:
K+πμ+μ invariant mass and angular distributions for the second q2 bin 2.00 <q2< 4.30 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Additional Figure 16:
K+πμ+μ invariant mass and angular distributions for the third q2 bin 4.30<q2<6.00 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Additional Figure 17:
K+πμ+μ invariant mass and angular distributions for the fourth q2 bin 6.00<q2<8.68 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Additional Figure 18:
K+πμ+μ invariant mass and angular distributions for the fifth q2 bin 10.09 <q2< 12.86 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Additional Figure 19:
K+πμ+μ invariant mass and angular distributions for the sixth q2 bin 14.18 <q2< 16.00 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Additional Figure 20:
K+πμ+μ invariant mass and angular distributions for the seventh q2 bin 16.00 <q2< 19.00 GeV2. Overlaid on each plot is the projection of the results for the total fit, as well as for the three components: correctly tagged signal, mistagged signal, and background. The vertical bars indicate the statistical uncertainties.

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Additional Figure 21:
Measured values of P1 versus q2 for B0K0μ+μ from CMS, compared with LHCb [1] results. The statistical uncertainty is shown by the inner vertical bars, while the outer vertical bars give the total uncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspond to the J/ψ and ψ resonances.

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Additional Figure 22:
Measured values of P5 versus q2 for B0K0μ+μ from CMS, compared with LHCb [1] and Belle [2] results. The statistical uncertainty is shown by the inner vertical bars, while the outer vertical bars give the total uncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspond to the J/ψ and ψ resonances.

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Additional Figure 23:
Measured values of P1 versus q2 for B0K0μ+μ from CMS, compared with LHCb [1] results. The statistical uncertainty is shown by the inner vertical bars, while the outer vertical bars give the total uncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspond to the J/ψ and ψ resonances. The red and blue hatched regions show two SM predictions averaging over each q2 bin to provide a direct comparison to the data. The SM-DHMV result is derived from Refs. [3,4], while SM-HEPfit result from Refs. [5,6]. Reliable theoretical predictions are not available near the J/ψ and ψ resonances.

png pdf
Additional Figure 24:
Measured values of P5 versus q2 for B0K0μ+μ from CMS, compared with LHCb [1] and Belle [2] results. The statistical uncertainty is shown by the inner vertical bars, while the outer vertical bars give the total uncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspond to the J/ψ and ψ resonances. The red and blue hatched regions show two SM predictions averaging over each q2 bin to provide a direct comparison to the data. The SM-DHMV result is derived from Refs. [3,4], while SM-HEPfit result from Refs. [5,6]. Reliable theoretical predictions are not available near the J/ψ and ψ resonances.

png pdf
Additional Figure 25:
Measured values of P5 versus q2 for B0K0μ+μ from CMS, compared with LHCb [1] results. The statistical uncertainty is shown by the inner vertical bars, while the outer vertical bars give the total uncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspond to the J/ψ and ψ resonances. The red and blue hatched regions show two SM predictions averaging over each q2 bin to provide a direct comparison to the data. The SM-DHMV result is derived from Refs. [3,4], while SM-HEPfit result from Refs. [5,6]. Reliable theoretical predictions are not available near the J/ψ and ψ resonances.

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Additional Figure 26:
Measured values of P5 versus q2 for B0K0μ+μ from CMS, compared with Belle [2] results. The statistical uncertainty is shown by the inner vertical bars, while the outer vertical bars give the total uncertainty. The horizontal bars show the bin widths. The vertical shaded regions correspond to the J/ψ and ψ resonances. The blue hatched region show the SM (SM-DHMV) predictions averaging over each q2 bin to provide a direct comparison to the data. The SM-DHMV prediction is derived from Refs. [3,4]. Reliable theoretical predictions are not available near the J/ψ and ψ resonances.
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Compact Muon Solenoid
LHC, CERN