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LHCb results presented at ICHEP 2016

3rd August 2016

Summary: Members of the LHCb collaboration, including many representatives from the UK, are presenting new results at ICHEP 2016

Image: ICHEP 2016 logo.

(Credit ICHEP2016)

This week sees the start of the big summer event in particle physics: the International Conference on High Energy Physics (ICHEP). This year it is hosted by the University of Chicago and many LHCb collaborators are now heading west to present the latest results from the experiment.



https://www.ichep2016.org/


One of the highlights is the first measurement of the photon polarisation in radiative B decays. This is a crucial measurement as the Standard Model (SM) of particle physics predicts that photons are predominantly left-handed, while many beyond-the-SM models predict enhanced amounts of the right-handed component. Handedness refers to how the photon's spin rotates about its direction of motion in either a clockwise or anticlockwise direction, referred to as right- or left-handed polarisation, respectively. The LHCb collaboration have used the full Run-1 data sample of Bs0 → φ γ decays to measure a quantity called AΔ, which is sensitive to the polarisation and is predicted to be AΔSM = 0.047+0.029-0.025 in the SM. LHCb has made the first measurement (LHCb-PAPER-2016-034) of this quantity to be AΔ = −0.98+0.46−0.52+0.23−0.20, which is compatible with the prediction.


Dr Tom Blake, Royal Society University research fellow and convenor of the working group that produced this results states that “This is a major milestone for us. In 2009 we set out a roadmap for six important measurements we wanted to make with the LHCb detector. This is the last measurement to be ticked off that list. With Run-2 data fast coming in we are looking forward to making even more precise tests of the photon polarisation predicted by the Standard Model.”.


Another new result is one of the first to use data recorded during in 2015 at the start of Run-2 of the LHC. With that dataset LHCb has measured (LHCb-PAPER-2016-031) the $b$ quark production cross-section, which tells us how often b-quark flavoured hadrons are produced at in the 13 TeV proton-proton collisions at the LHC. The measured value is 164.9 ± 2.3 ± 14.6 micro-barns, which means that for every inverse micro-barn of data collected by the LHCb experiment in Run-2, approximately 165 b-hadrons are produced within the LHCb detector acceptance. Given that LHCb has already collected over 1 inverse femtobarn of 13 TeV collisions, this means that the experiment has recorded more than 165 × 109 b-hadrons! This large sample will allow LHCb to make even more precise measurements of b-quark properties in the future.


Dr Greig Cowan, STFC Ernest Rutherford fellow, helped produced the cross-section result states that “This result is a benchmark for the LHCb experiment that will be used to constrain and influence theoretical models that predict the properties of b-quark production. By measuring this basic quantity we have shown that the LHCb detector is fully operational in Run-2 and can look forward to a host of new measurements in the coming months.”.


LHCb will present new results from over 20 publications and conference reports. These include observations of extremely rare B meson decay modes, new constraints on CP violation effects in both charm and beauty sectors and first results with LHCb's new HERSCHEL subdetector.


Contacts:


Dr Tom Blake, T.Blake.1ATNOSPAMwarwick.ac.uk

Dr Greig Cowan, g.cowanATNOSPAMed.ac.uk


LHCb-UK:

The UK participation in the international LHCb experiment is from eleven institutes.

University of Birmingham, University of Bristol, University of Cambridge, University of Edinburgh, University of Glasgow, Imperial College London, University of Liverpool, University of Manchester, University of Oxford, STFC Rutherford Appleton Laboratory, University of Warwick


UK participation in the experiment is funded by the Science and Technology Facillities Council (STFC), with contributions from the participating institutes, the Royal Society and European Union.