Explore the vast range of titles available.

The NA48/2 experiment at CERN reports the first observation of the K^(±) → π⁰π⁰μ^(±)ν decay based on a sample of 2437 candidates with 15% background contamination collected in 2003–2004. The decay branching ratio in the kinematic region of the squared dilepton mass above 0.03 GeV2/c4 is measured to be (0.65 ± 0.03) × 10–6. The extrapolation to the full kinematic space, using a specific model, is found to be (3.45 ± 0.16) × 10–6, in agreement with chiral perturbation theory predictions.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).Measurements are presented of electroweak boson production using data from pp collisions at a centre-of-mass energy of ... TeV. The analysis is based on an integrated luminosity of 2.0 fb super(-1) recorded with the LHCb detector. The bosons are identified in the W arrow right mu nu and Z arrow right mu super(+) mu super(-) decay channels. The cross-sections are measured for muons in the pseudorapidity range 2.0 < eta < 4.5, with transverse momenta p sub(T) > 20 GeV/c and, in the case of the Z boson, a dimuon mass within ... GeV/c super(2). The results are ... ... ... ... ... ... ... ... where the first uncertainties are statistical, the second are systematic, the third are due to the knowledge of the LHC beam energy and the fourth are due to the luminosity determination. The evolution of the W and Z boson cross-sections with centre-of-mass energy is studied using previously reported measurements with 1.0 fb super(-1) of data at 7 TeV. Differential distributions are also presented. Results are in good agreement with theoretical predictions at next-to-next-to-leading order in perturbative quantum chromodynamics. [Figure not available: see fulltext.]

A measurement of CP-violating observables is performed using the decays B $^{±}$→ DK $^{±}$and B $^{±}$→ Dπ $^{±}$ , where the D meson is reconstructed in one of the self-conjugate three-body final states$ {K}_{\\mathrm{S}}^0 $ π $^{+}$ π $^{−}$and$ {K}_{\\mathrm{S}}^0 $ K $^{+}$ K $^{−}$(commonly denoted$ {K}_{\\mathrm{S}}^0 $ h $^{+}$ h $^{−}$ ). The decays are analysed in bins of the D-decay phase space, leading to a measurement that is independent of the modelling of the D-decay amplitude. The observables are inter- preted in terms of the CKM angle γ. Using a data sample corresponding to an integrated luminosity of 9 fb $^{−1}$collected in proton-proton collisions at centre-of mass energies of 7, 8, and 13 TeV with the LHCb experiment, γ is measured to be$ \\left({68.7}_{-5.1}^{+5.2}\\right){}^{\\circ} $ . The hadronic parameters$ {r}_B^{D K},{r}_B^{D\\pi},{\\delta}_B^{D K},\\kern0.5em \\mathrm{and}\\kern0.5em {\\delta}_B^{D\\pi} $ , which are the ratios and strong-phase differences of the suppressed and favoured B $^{±}$decays, are also reported.[graphic not available: see fulltext]

We report results from a new measurement of the K e4 decay K ± →π + π - e ± ν by the NA48/2 collaboration at the CERN SPS, based on a partial sample of more than 670 000 K e4 decays in both charged modes collected in 2003. The form factors of the hadronic current (F,G,H) and ππ phase difference (δ=δ s -δ p ) have been measured in ten independent bins of the ππ mass spectrum to investigate their variation. A sizeable acceptance at large ππ mass, a low background and a very good resolution contribute to an improved experimental accuracy, a factor two better than in the previous measurement, when extracting the ππ scattering lengths a 0 0 and a 0 2 . Under the assumption of isospin symmetry and using numerical solutions of the Roy equations, the following values are obtained in the plane (a 0 0 ,a 0 2 ): a 0 0 =0.233±0.016stat±0.007syst,a 0 2 =-0.0471±0.011stat±0.004syst. The presence of potentially large isospin effects is also considered and will allow comparison with precise predictions from Chiral Perturbation Theory.

The NA62 experiment at CERN collected the world’s largest dataset of charged kaon decays in 2016–2018, leading to the first measurement of the branching ratio of the ultra-rare K + → π + vv − decay, based on 20 candidates. Recent results from analyses of K + → π 0 e + v γ, K + → π + µ + µ − and K + → π + γγ decays, using a data sample recorded in 2017-2018, are reported. Preliminary results of the first observation and analysis of the K ± → π 0 π 0 µ ± v decay, based on the NA48/2 data collected in 2003-2004, are also shown.

A search is performed for the as yet unobserved baryonic Λb→Λη′ and Λb→Λη decays with 3fb−1 of proton-proton collision data recorded by the LHCb experiment. The B0→K0Sη′ decay is used as a normalisation channel. No significant signal is observed for the Λb→Λη′ decay. An upper limit is found on the branching fraction of B(Λb→Λη′)<3.1×10−6 at 90% confidence level. Evidence is seen for the presence of the Λb→Λη decay at the level of 3σ significance, with a branching fraction B(Λb→Λη)=(9.3+7.3−5.3)×10−6.

A measurement of the form factors of charged kaon semileptonic decays is presented, based on 4.4 × 106K± → π0e±νe (K e3 ± ) and 2.3 × 106K± → π0μ±νμ (K μ3 ±) decays collected in 2004 by the NA48/2 experiment. The results are obtained with improved precision as compared to earlier measurements. The combination of measurements in the K e3 ± and K μ3 ± modes is also presented.

Abstract The NA48/2 experiment at CERN reports the first observation of the K ± → π 0 π 0 μ ± ν decay based on a sample of 2437 candidates with 15% background contamination collected in 2003–2004. The decay branching ratio in the kinematic region of the squared dilepton mass above 0.03 GeV2/c 4 is measured to be (0.65 ± 0.03) × 10 −6. The extrapolation to the full kinematic space, using a specific model, is found to be (3.45 ± 0.16) × 10 −6, in agreement with chiral perturbation theory predictions.

A measurement of Z → τ ⁺ τ ⁻production cross-section is presented using data, corresponding to an integrated luminosity of 2 fb ⁻¹ , from pp collisions at √s̅=8 TeV collected by the LHCb experiment. The τ ⁺ τ ⁻candidates are reconstructed in final states with the first tau lepton decaying leptonically, and the second decaying either leptonically or to one or three charged hadrons. The production cross-section is measured for Z bosons with invariant mass between 60 and 120 GeV/c ² , which decay to tau leptons with transverse momenta greater than 20 GeV/c and pseudorapidities between 2.0 and 4.5. The cross-section is determined to be σ_(pp)_(→ Z→ τ⁺)_(τ⁻)=95.8 ± 2.1 ± 4.6 ± 0.2 ± 1.1 pb, where the first uncertainty is statistical, the second is systematic, the third is due to the LHC beam energy uncertainty, and the fourth to the integrated luminosity uncertainty. This result is compatible with NNLO Standard model predictions. The ratio of the cross-sections for Z → τ ⁺ τ ⁻to Z → μ ⁺ μ ⁻(Z → e ⁺ e ⁻ ), determined to be 1.01 ± 0.05 (1.02 ± 0.06), is consistent with the lepton-universality hypothesis in Z decays.

A study ofB⁰_(s) → η_(c) φandB⁰_(s) → η_(c) π⁺π⁻decays is performed usingppcollision data corresponding to an integrated luminosity of 3.0 \\rm fb⁻¹ , collected with the LHCb detector in Run 1 of the LHC. The observation of the decayB⁰_(s) → η_(c) φis reported, where theη_(c)meson is reconstructed in thepp̄ ,K⁺K⁻π⁺π⁻ ,π⁺π⁻π⁺π⁻andK⁺K⁻K⁺K⁻decay modes and theφ(1020)in theK⁺ K⁻decay mode. The decayB⁰_(s) → J/ψ φis used as a normalisation channel. Evidence is also reported for the decayB⁰_(s) → η_(c) π⁺π⁻ , where theη_(c)meson is reconstructed in thepp̄decay mode, using the decayB⁰_(s) → J/ψ π⁺ π⁻as a normalisation channel. The measured branching fractions are eqnarray* B (B⁰_(s) _(c) ) &=& (5.01 0.53 0.27 0.63 ) 10⁻4 , B (B⁰_(s) _(c) ⁺ ⁻) &=& (1.76 0.59 0.12 0.29 ) 10⁻4 , eqnarray* where in each case the first uncertainty is statistical, the second systematic and the third uncertainty is due to the limited knowledge of the external branching fractions.