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Register a new userPrecision luminosity measurements at LHCb
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Measuring cross-sections at the LHC requires the luminosity to be determined accurately at each centre-of-mass energy $sqrt{s}$. In this paper results are reported from the luminosity calibrations carried out at the LHC interaction point 8 with the LHCb detector for $sqrt{s}$ = 2.76, 7 and 8 TeV (proton-proton collisions) and for $sqrt{s_{NN}}$ = 5 TeV (proton-lead collisions). Both the van der Meer scan and beam-gas imaging luminosity calibration methods were employed. It is observed that the beam density profile cannot always be described by a function that is factorizable in the two transverse coordinates. The introduction of a two-dimensional description of the beams improves significantly the consistency of the results. For proton-proton interactions at $sqrt{s}$ = 8 TeV a relative precision of the luminosity calibration of 1.47% is obtained using van der Meer scans and 1.43% using beam-gas imaging, resulting in a combined precision of 1.12%. Applying the calibration to the full data set determines the luminosity with a precision of 1.16%. This represents the most precise luminosity measurement achieved so far at a bunched-beam hadron collider.
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Absolute luminosity measurements are of general interest for colliding-beam experiments at storage rings. These measurements are necessary to determine the absolute cross-sections of reaction processes and are valuable to quantify the performance of the accelerator. Using data taken in 2010, LHCb has applied two methods to determine the absolute scale of its luminosity measurements for proton-proton collisions at the LHC with a centre-of-mass energy of 7 TeV. In addition to the classic van der Meer scan method a novel technique has been developed which makes use of direct imaging of the individual beams using beam-gas and beam-beam interactions. This beam imaging method is made possible by the high resolution of the LHCb vertex detector and the close proximity of the detector to the beams, and allows beam parameters such as positions, angles and widths to be determined. The results of the two methods have comparable precision and are in good agreement. Combining the two methods, an overall precision of 3.5% in the absolute luminosity determination is reached. The techniques used to transport the absolute luminosity calibration to the full 2010 data-taking period are presented.
These proceedings present the current status of measurements of the CP-violating phase $phi_s$ by the LHCb collaboration, reviewing the measurements in channels such as $B_s^0to J/psiphi$, $B_s^0to J/psi pi^+pi^-$ and $B_s^0 to psi(2S)phi$. The observation of the $B_s^0toeta_cphi$ decay mode is presented for the first time, which can be used to measure $phi_s$ with larger data samples that will be collected over the coming years by the LHCb experiment. Finally, the expected increase in precision from LHCb measurements of $phi_s$ over the next decade is presented.
This report details the capabilities of LHCb and its upgrades towards the study of kaons and hyperons. The analyses performed so far are reviewed, elaborating on the prospects for some key decay channels, while proposing some new measurements in LHCb to expand its strangeness research program.
A method to measure integrated luminosities at the LHC using Z bosons without theoretical cross section input is discussed. The main uncertainties and the prospects for precision luminosity measurements using this method are outlined.
The prospects for electroweak precision measurements at the Future Circular Collider with electron-positron beams (FCC-ee) are discussed. The Z mass and width, as well as the value of the electroweak mixing angle, can be measured with very high precision at the Z pole thanks to an instantaneous luminosity five to six order of magnitudes larger than LEP. At centre-of-mass energies around 160 GeV, corresponding to the WW production threshold, the W mass can be determined very precisely with high-statistics cross section measurements at several energy points. Similarly, a very precise determination of the top mass can be provided by an energy scan at the $mathrm{t bar t}$ production threshold, around 350 GeV.
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