Measurement of the differential branching fraction and A CP of the rare decay B + → π + µ + µ −
File(s)
Author(s)
Murta, Rebecca
Type
Thesis
Abstract
This thesis presents an analysis of the rare decay B+ → π+μ+μ−. The differential branching
fraction is measured in bins of the dimuon invariant mass squared, q2. The branching fraction
ratio with the decay B+ → K+μ+μ− is measured in the same bins. World-leading precision is
achieved, and the first binned measurement is made of the B+ → π+μ+μ− CP asymmetry. The
total B+ → π+μ+μ− branching fraction is obtained from the measured differential branching
fraction in each q2 bin:
B(B+ → π+μ+μ−) =(︁ 1.985+0.122
−0.112 (stat) ± 0.131 (syst))︁ × 10−8.
The total ACP is found to be
ACP (B− → π−μ+μ−) = −0.034+0.061
−0.060 (stat) ± 0.015 (syst).
The results are obtained using 9 fb−1 of data collected by the LHCb detector at CERN, at centre-
of-mass energies of 7, 8 and 13 TeV. A comparison is made to Standard Model predictions,
with the results showing good agreement with the expectation, within 2.0σ. Fits to the results
for different Wilson coefficients are carried out, showing consistency with the Standard Model
within less than 0.5σ.
fraction is measured in bins of the dimuon invariant mass squared, q2. The branching fraction
ratio with the decay B+ → K+μ+μ− is measured in the same bins. World-leading precision is
achieved, and the first binned measurement is made of the B+ → π+μ+μ− CP asymmetry. The
total B+ → π+μ+μ− branching fraction is obtained from the measured differential branching
fraction in each q2 bin:
B(B+ → π+μ+μ−) =(︁ 1.985+0.122
−0.112 (stat) ± 0.131 (syst))︁ × 10−8.
The total ACP is found to be
ACP (B− → π−μ+μ−) = −0.034+0.061
−0.060 (stat) ± 0.015 (syst).
The results are obtained using 9 fb−1 of data collected by the LHCb detector at CERN, at centre-
of-mass energies of 7, 8 and 13 TeV. A comparison is made to Standard Model predictions,
with the results showing good agreement with the expectation, within 2.0σ. Fits to the results
for different Wilson coefficients are carried out, showing consistency with the Standard Model
within less than 0.5σ.
Date Issued
2024-05-21
Date Awarded
01/02/2025
License URL
Advisor
McCann, Michael
Sponsor
Science and Technology Facilities Council (Great Britain)
Publisher Department
Department of Physics
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)