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This thesis presents a study of a method for identifying b-jets by searching for “soft” muons produced within them. This method, a so-called Soft Muon Tagger, uses the quality of the match (Χ2match) between tracks left in the inner detector and the muon systems within the ATLAS detector to discriminate between muons within hadronic jets produced by the decay of b quarks, and those within light flavour jets. The complete characteristics of the tagger are investigated in a detailed study on simulated data. The scale factors between the efficiency of the tagger in simulated and collision data, dependent on the kinematics of the tagged muon, are found using J/Ψ decays. These are used in a measurement of the top quark pair production cross section in collision data. The measurement is performed on data taken during the 2011 run of the LHC, specifically in the lepton+jets top-antitop quark decay channel. A summary of this measurement is presented, and is found to be compatible with theoretical predictions for the cross section at a centre of mass energy of √s = 7 TeV, and with published ATLAS and CMS measurements using b-tagging in the lepton+jets channel. The measured cross section is: σtt ̄ = 165 ± 2(stat.) ± 17(syst.) ± 3(lumi.) pb The Χ2match-based soft muon tagger contributes a small b-tagging systematic uncertainty to the cross section measurement compared to measurements performed using lifetime based b-taggers, and has a good signal to background ratio.

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Results are presented on the production of singly strange \(\Lambda\) and \(\overline{\Lambda}\) hyperons and K\(^0\)\(_S\) mesons in p-Be collisions at 40 GeV/c beam momentum. The data were obtained by the NA57 experiment at the CERN SPS in the 1999 data taking period. A comprehensive study of yields and transverse mass spectra for each of the three particle species is given. The results are compared to Pb-Pb data at 40 A GeV/c. In particular, the yields per wounded nucleon are seen to increase for all three particle species when going from p-Be to Pb-Pb collisions. This is a proposed signature that makes the transition of hadronic matter into a new phase of matter known as a Quark-Gluon Plasma (QGP). An overview of QGP physics, its signatures and experimental results together with its importance to the understanding of QCD is given. The NA57 experimental apparatus is described in detail and the analysis procedures and techniques along with the results detailed. A study of the systematics is made. The results are compared to WA97/NA57 results at the top SPS energy and to results from other SPS and RHIC experiments. A brief insight into future experiments that will study the QGP is given.

I describe a calculation of the B*Bπ coupling in lattice QCD. The B*Bπ coupling is directly related to gb, the leading order low-energy interaction constant of heavy meson chiral perturbation theory. Knowledge of the coupling will help decrease systematic uncertainties in lattice QCD B-physics studies, which are important to constrain the CKM matrix and probe the Standard Model. This calculation is performed with 2+1 flavours of dynamic quarks using the domain wall fermion action. To simulate the heavy b-quark I use a non-perturbatively tuned relativistic heavy quark action which keeps discretisation effects under good control. This allows me to make the first calculation of the B*Bπ coupling directly at the physical b-quark mass. I conduct a chiral and continuum extrapolation to the physical point and consider all sources of systematic error. The final result including both statistical and sytematic errors is gb = 0.567(52)stat(58)sys.

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A central goal of flavour physics is a precise determination of the elements of the CKM matrix, which quantifies the strength of charged-current weak interactions between quarks. Of particular interest is the angle γ in the 'b-d' unitarity triangle parameterisation of the CKM matrix. One of the most promising methods to determine γ directly is to measure CP violation in interfering B±->DK± decays, where D indicates a coherent superposition of D0 and D0bar, both of which decay to the same final state. When using this method it is essential to determine the hadronic decay parameters of the D precisely in order to reduce the systematic uncertainties on the measurement of γ. One such parameter is the strong-phase difference between D0 and D0bar decays, which must be accurately known across the entire kinematic phase space. In this thesis we present measurements related to the determination of γ at both the CLEO-c experiment at Cornell University and the LHCb experiment at CERN. Firstly, we describe a model-independent determination of the D->KsKK strong-phase difference using 818pb-1 of quantum-correlated D0-D0bar data collected by CLEO-c at the ψ(3770) resonance. We reconstruct D->KsKK decays tagged with a variety of final states. By studying these decays we determine the weighted cosine and sine of the strong-phase difference in bins across the Dalitz plane. We run simulations to estimate the impact of these measurements on a determination of γ using B±->D(KsKK)K± decays. The resulting uncertainty on γ due to the CLEO-c inputs is between 3.2° and 3.9°, depending on how the Dalitz plane is binned. Furthermore, we present a model-independent measurement of the CP content of the decay D0->KsKK in the kinematic region of the φ->KK resonance. The fraction of CP-odd events in this region is 0.76 or higher at the 90% C.L. We also present an analysis of data recorded by LHCb in 2010, corresponding to an integrated luminosity of 36.5pb-1. We reconstruct the decays B±->D(Kπ)h± and B±->D(KK)h±, where h± indicates either K± or π±. Although there are not enough events in this dataset to measure γ, we are able to measure other observables related to CP violation in the B±->Dh± system. We measure B(DK,Fav)/B(Dπ,Fav), the ratio of the branching fraction of B±->D(Kπ)K± to that of B±->D(Kπ)π±, to be 0.066 ± 0.005 ± 0.004, and B(DK,CP)/B(Dπ,CP), the ratio of the branching fraction of B±->D(KK)K± to that of B±->D(KK)π±, to be 0.093 ± 0.019 ± 0.005. We determine several CP asymmetries: A(CP+,DK), the CP asymmetry in B±->D(KK)K± decays, is measured as 0.06 ± 0.17 ± 0.07; A(CP+,Dπ), the CP asymmetry in B±->D(KK)π± decays, is found to be 0.009 ± 0.042 ± 0.011; and A(Fav,DK), the CP asymmetry in B±->D(Kπ)K± decays, is measured as -0.109 ± 0.085 ± 0.019. Finally we calculate R(CP+), the ratio of the branching fraction of B±->D(KK)K± to that of B±->D(Kπ)K±, to be 1.41 ± 0.31 ± 0.11. These results indicate that LHCb is in a strong position to make a world-leading measurement of γ with a larger data sample.