It looks like the tensions suggesting lepton universality violations in B meson decays (contrary to the Standard Model prediction) have disappeared with improved amounts of data and improved data quality at the LHC, according to two preprints released today, in another glorious (but unexciting) victory for the Standard Model of Particle Physics.
The first simultaneous test of muon-electron universality using B+→K+ℓ+ℓ− and B0→K∗0ℓ+ℓ− decays is performed, in two ranges of the dilepton invariant-mass squared, q2. The analysis uses beauty mesons produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb−1. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model.
LHCb collaboration, "Test of lepton universality in b→sℓ+ℓ− decays" arXiv:2212.09152 (December 18, 2022) (All figures and tables, along with any supplementary material and additional information, are available at this https URL (LHCb public pages)).
A simultaneous analysis of the B+→K+ℓ+ℓ− and B0→K∗0ℓ+ℓ− decays is performed to test muon-electron universality in two ranges of the square of the dilepton invariant mass, q2. The measurement uses a sample of beauty meson decays produced in proton-proton collisions collected with the LHCb detector between 2011 and 2018, corresponding to an integrated luminosity of 9 fb−1. A sequence of multivariate selections and strict particle identification requirements produce a higher signal purity and a better statistical sensitivity per unit luminosity than previous LHCb lepton universality tests using the same decay modes. Residual backgrounds due to misidentified hadronic decays are studied using data and included in the fit model. Each of the four lepton universality measurements reported is either the first in the given q2 interval or supersedes previous LHCb measurements. The results are compatible with the predictions of the Standard Model.
LHCb collaboration, "Measurement of lepton universality parameters in B+→K+ℓ+ℓ− and B0→K∗0ℓ+ℓ− decays" arXiv:2212.09153 (December 18, 2022) (All figures and tables, along with any supplementary material and additional information, are available at this https URL (LHCb public pages).
The announcement of the result generated this meme:
why's there a special interest in another HE-LHC upgrade to 28 TEV better quality of data
ReplyDeleteHE-LHC: This would essentially be a higher energy version of the LHC, in the same tunnel, built using higher field (16 T vs. 8.33 T) magnets. It would operate at a CM energy of 27 TeV. The drawbacks are that, while construction would be challenging (there are not yet appropriate 16 T magnets), only a modest (27 vs. 14 TeV) increase in CM energy would be achieved. The big advantage over the FCC-hh is cost: much of the LHC infrastructure could be reused and the machine is smaller, so the total cost estimate is about $7 billion.
also note that --
Conclusions
A spectrometric system integrating TPX3, MWPC and TPC detectors is under construction with the goal of measuring the angular correlation of e
e pairs created in the deexcitation of Be and He nuclei. A triangle TPX3 experiment was setup to develop the particle track reconstruction. The reconstruction of 3D tracks in TPX3 detectors allows us to compensate for target misalignments and determine the position of its centre, necessary for the calculations of the angular correlations.
https://www.sciencedirect.com/science/article/abs/pii/S0168900222011500?via%3Dihub