Marwa Jahjah-Hussein

First evidence for the decay Bs -> mu+ mu-

A search for the rare decays B(s)(0)→μ+ μ- and B(0)→μ+ μ- is performed with data collected in 2011 and 2012 with the LHCb experiment at the Large Hadron Collider. The data samples comprise 1.1  fb(-1) of proton-proton collisions at sqrt[s]=8  TeV and 1.0  fb(-1) at sqrt[s]=7  TeV. We observe an excess of B(s)(0)→μ+ μ- candidates with respect to the background expectation. The probability that the background could produce such an excess or larger is 5.3×10(-4) corresponding to a signal significance of 3.5 standard deviations. A maximum-likelihood fit gives a branching fraction of B(B(s)(0)→μ+ μ-)=(3.2(-1.2)(+1.5))×10(-9), where the statistical uncertainty is 95% of the total uncertainty. This result is in agreement with the standard model expectation. The observed number of B(0)→μ+ μ- candidates is consistent with the background expectation, giving an upper limit of B(B(0)→μ+ μ-)<9.4×10(-10) at 95% confidence level.

Search for the rare decay K^0_S -> mu+ mu-

A search for the decay K0S→μ+μ− is performed, based on a data sample of 1.0 fb−1 of pp collisions at √ s =7 TeV collected by the LHCb experiment at the Large Hadron Collider. The observed number of candidates is consistent with the background-only hypothesis, yielding an upper limit of B(K0S→μ+μ−) < 11(9) × 10−9 at 95 (90)% confidence level. This limit is a factor of thirty below the previous measurement.A bstractA search for the decay

Differential branching fraction and angular analysis of the B +→ K+μ+μ- decay

K_{\mathrm{S}}^0\to {\mu^{+}}{\mu^{-}}

Measurement of ψ(2S) meson production in pp collisions at √s = 7 TeV

is performed, based on a data sample of 1.0 fb−1 of pp collisions at

Measurement of relative branching fractions of B decays to psi(2S) and J/psi mesons

\sqrt{s}=7\;\mathrm{TeV}

Study of

collected by the LHCb experiment at the Large Hadron Collider. The observed number of candidates is consistent with the background-only hypothesis, yielding an upper limit of

D_{sJ}

\mathcal{B}\left( {K_{\mathrm{S}}^0\to {\mu^{+}}{\mu^{-}}} \right)

decays to

< 11(9) × 10−9 at 95 (90)% confidence level. This limit is a factor of thirty below the previous measurement.

D^+\KS

A bstractThe angular distribution and differential branching fraction of the decay B+→ K+μ+μ− are studied with a dataset corresponding to 1.0fb−1 of integrated luminosity, collected by the LHCb experiment. The angular distribution is measured in bins of dimuon invariant mass squared and found to be consistent with Standard Model expectations. Integrating the differential branching fraction over the full dimuon invariant mass range yields a total branching fraction of

and

\mathcal{B}