Evidence of CP violation in charmless three-body decays $B^\pm\rightarrow K^\pm\pi^+\pi^-$, $B^\pm\rightarrow K^\pm K^+K^-$, $B^\pm\rightarrow K^+ K^-\pi^\pm$ and $B^\pm\rightarrow \pi^\pm\pi^+\pi^-$

In this work we present a measurement of the ratio of the branching fraction of the radiative decays $B^{0}\rightarrow K^{*0}\gamma$ and $B^{0}_{s}\rightarrow \phi\gamma$ using 1.0 fb$^{-1}$ of data taken with the LHCb detector. The value obtained is \begin{equation} \frac{B\left(B^{0}\rightarrow K^{*0}\gamma\right)}{B\left(B^{0}_{s}\rightarrow \phi\gamma\right)}=1.23\pm0.06(stat.)\pm0.04(syst.)\pm0.10\left(f_s/f_d\right) \end{equation} Using the world average value $B\left(B^{0}\rightarrow K^{*0}\gamma\right)=\left(4.33\pm0.15\right)\times10^{-5}$ branching fraction is determined to be $B\left(B^{0}_{s}\rightarrow \phi\gamma\right)=3.5\pm0.4\times10^{-5}$. A measurement of the direct CP asymmetry of the decay $B^{0}\rightarrow K^{*0}\gamma$ is also presented. Both measurements are the most precise to date and are in agreement with the previous experimental results and theoretical expectations.

The LHCb purposes are to make precise measurements of $B$ and $D$ meson decays. In particular in time-dependent CP violation studies the determination of $B$ flavour at production is fundamental. This is known as "flavour tagging" and at LHCb it is performed with several algorithms. The performances and calibration of the flavour tagging algorithms with 2011 data collected by LHCb are reported. Also the performances of the flavour tagging algorithms in the relevant CP violation and asymmetry studies are also reported.

The LHCb detector was conceived to operate with an average Luminosity of $2 \times 10^{32}$ cm$^{-2}$ s$^{-1}$. During the last year of LHC run, the whole apparatus has shown to be able to perfectly acquire and manage data produced at a Luminosity as high as $4 \times 10^{32}$ cm$^{-2}$ s$^{-1}$. In these conditions, all sub-detectors operated at average particle rates higher than the design ones and in particular the Multi-Wire Proportional Chambers equipping the Muon System had to sustain a particle rate as high as 250 kHz/cm$^{2}$. In order to study the possibility of increasing the Luminosity of operation of the whole experiment several tests were performed. The effective beam Luminosity at the interaction point of LHCb was increased in several steps up to $10^{33}$ cm$^{-2}$ s$^{-1}$ and in each step the behavior of all the detectors in the Muon System was recorded. The data analysis has allowed to study the performance of the Muon System as a function of the LHC Luminosity and the results are reported in this presentation.

Charmless $B \to 3$ body decays at LHCb

Use a model independent binned method to search for CP violation in singly Cabibbo suppressed four body charm decays. CP violation $\succ \mathcal {O}(10^{-3})$ would point toward new physics.

LHCb is fully instrumented in the forward region, $2 \leq \eta \leq 5$, and provides compelentary results to the central measurements of ATLAS and CMS. Preliminary limits are presented on neutral Higgs production usint $\tau \tau$ final states in the forward region of LHCb.

A search for non-resonant $D^{+}_{(s)} \rightarrow \pi^+ \mu^+ \mu^-$ and $D^{+}_{(s)} \rightarrow \pi^- \mu^+ \mu^+$ decays is performed using 1.0 $fb^{-1}$ of proton-proton collisions at s = 7 TeV recorded by the LHCb experiment. No signals are observed and the world's best limits on the branching fractions are set.

On the poster three LHCb results on B meson mixing using a datasample of 1 fb$^{-1}$ of $pp$ collisions at $\sqrt{s} =$ 7 TeV are presented. The B meson oscillation frequencies are measured as $\Delta m_d = 0.5156 \pm 0.0051 (\text{stat}) \pm 0.0033 (\text{syst}) \text{ps}^{-1}$ and $\Delta m_s = 17.768 \pm 0.023 (\text{stat}) \pm 0.006 (\text{syst}) \text{ps}^{-1}$. The CP violation observables in the decay channel $B^0 \rightarrow J/\psi K^0_S$ are determined as $S_{J/\psi K^0_S} = 0.73 \pm 0.07 (\text{stat})\pm 0.04 (\text{syst})$ and $C_{J/\psi K^0_S} = 0.03 \pm 0.09 (\text{stat})\pm 0.01 (\text{syst})$.

The LHCb purposes are to make precise measurements in $B$ and $D$ meson decays. In particular in time-dependent CP violation studies the determination of $B$ flavour at production ("Flavour Tagging") is fundamental. The performances and calibration of the flavour tagging algorithms with 2011 data collected by LHCb are reported. The performances of the flavour tagging algorithms on the relevant CP violation and asymmetry studies are also reported.