Energy dependence of ϕ meson production at forward rapidity in pp collisions at the LHC

The production of $\phi$ mesons has been studied in pp collisions at LHC energies with the ALICE detector via the dimuon decay channel in the rapidity region $2.5< y < 4$. Measurements of the differential cross section $\mathrm{d}^2\sigma /\mathrm{d}y \mathrm{d}p_{\mathrm {T}}$ are presented as a function of the transverse momentum ($p_{\mathrm {T}}$) at the center-of-mass energies $\sqrt{s}=5.02$, 8 and 13 TeV and compared with the ALICE results at midrapidity. The differential cross sections at $\sqrt{s}=5.02$ and 13 TeV are also studied in several rapidity intervals as a function of $p_{\mathrm {T}}$, and as a function of rapidity in three $p_{\mathrm {T}}$ intervals. A hardening of the $p_{\mathrm {T}}$-differential cross section with the collision energy is observed, while, for a given energy, $p_{\mathrm {T}}$ spectra soften with increasing rapidity and, conversely, rapidity distributions get slightly narrower at increasing $p_{\mathrm {T}}$. The new results, complementing the published measurements at $\sqrt{s}=2.76$ and 7 TeV, allow one to establish the energy dependence of $\phi$ meson production and to compare the measured cross sections with phenomenological models. None of the considered models manages to describe the evolution of the cross section with $p_{\mathrm {T}}$ and rapidity at all the energies.publishedVersio

Measurement of the CKM angle γ using the B± → D*h± channels

A measurement of the CP-violating observables from B± → D*K± and B± → D*π± decays is presented, where D*(D) is an admixture of D*0 and D¯∗0 (D0 and D¯0) states and is reconstructed through the decay chains D*→ Dπ0/γ and D→KS0π+π−/KS0K+K−. The measurement is performed by analysing the signal yield variation across the D decay phase space and is independent of any amplitude model. The data sample used was collected by the LHCb experiment in proton-proton collisions and corresponds to a total integrated luminosity of 9 fb−1 at centre-of-mass energies of 7, 8 and 13 TeV. The CKM angle γ is determined to be 69−14+13∘ using the measured CP-violating observables. The hadronic parameters rBD∗K±, rBD∗π±, δBD∗K±, δBD∗π±, which are the ratios and strong phase differences between favoured and suppressed B± decays, are also reported

Measurement of prompt D+ and Ds+ production in pPb collisions at √sNN = 5. 02 TeV

The production of prompt D+ and D+s mesons is studied in proton-lead collisions at a centre-of-mass energy of √sNN = 5.02 TeV. The data sample corresponding to an integrated luminosity of (1.58 ± 0.02)nb−1 is collected by the LHCb experiment at the LHC. The differential production cross-sections are measured using D+ and D+s candidates with transverse momentum in the range of 0 &lt; pT &lt; 14 GeV/c and rapidities in the ranges of 1.5 &lt; y∗ &lt; 4.0 and –5.0 &lt; y∗ &lt; –2.5 in the nucleon-nucleon centre-of-mass system. For both particles, the nuclear modification factor and the forward-backward production ratio are determined. These results are compared with theoretical models that include initial-state nuclear effects. In addition, measurements of the cross-section ratios between D+, D+s and D0 mesons are presented, providing a baseline for studying the charm hadronization in lead-lead collisions at LHC energies

Alternatives for Conventional Alkane Solvents

The studies described in this paper show that hydrocarbon oligomers are alternatives for low molecular weight alkane solvents. These oligomeric solvents are nontoxic, nonvolatile, and recyclable alternatives to heptane in thermomorphic solvent mixtures that use a polar solvent such as methanol, aqueous ethanol, or DMF or in biphasic mixtures that use acetonitrile. Regardless of which polar solvent is used, hydrocarbon oligomers like poly­(α-olefin)­s (PAOs) exhibit very low leaching into the polar phase. UV–visible spectroscopy studies show that these solvents have the solubility properties of heptane. For example, PAOs dissolve heptane soluble dyes and quantitatively separate them from polar phases in thermomorphic solvent mixtures. PAOs either as pure solvents or as additives in heptane act as antileaching agents, decreasing the already low leaching of such dyes into a polar phase in heptane/polar solvent mixtures. These oligomeric hydrocarbon solvents were also compared to heptane in studies of azo dye isomerization. The results show that thermal isomerization of an azo dye occurs at the same rate in heptane and a PAO. Further studies of carboxylic acid promoted dye isomerization in heptane and a PAO show that low molecular weight and oligomeric carboxylic acids are kinetically equivalent at accelerating this isomerization. The results suggest that these and other hydrocarbon oligomers behave as solvents like their low molecular weight nonpolar hydrocarbon solvents and that they can be substituted successfully for conventional solvents like heptane

Observation of New Baryons in the Ξ_{b}^{-}π^{+}π^{-} and Ξ_{b}^{0}π^{+}π^{-} Systems.

The first observation and study of two new baryonic structures in the final state Ξ_{b}^{0}π^{+}π^{-} and the confirmation of the Ξ_{b}(6100)^{-} state in the Ξ_{b}^{-}π^{+}π^{-} decay mode are reported using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9  fb^{-1}. In addition, the properties of the known Ξ_{b}^{*0}, Ξ_{b}^{'-} and Ξ_{b}^{*-} resonances are measured with improved precision. The new decay mode of the Ξ_{b}^{0} baryon to the Ξ_{c}^{+} π^{-} π^{+} π^{-} final state is observed and exploited for the first time in these measurements

Search for the baryon- and lepton-number violating decays <math display="inline"><msup><mi>B</mi><mn>0</mn></msup><mo stretchy="false">→</mo><mi>p</mi><msup><mi>μ</mi><mo>-</mo></msup></math> and <math display="inline"><msubsup><mi>B</mi><mi>s</mi><mn>0</mn></msubsup><mo stretchy="false">→</mo><mi>p</mi><msup><mi>μ</mi><mo>-</mo></msup></math>

International audienceA search for the baryon- and lepton-number violating decays B0→pμ- and Bs0→pμ- is performed at the LHCb experiment using data collected in proton-proton collisions at s=7, 8 and 13 TeV, corresponding to integrated luminosities of 1, 2, and 6  fb-1, respectively. No significant signal for B0→pμ- and Bs0→pμ- decays is found and the upper limits on the branching fractions are determined to be B(B0→pμ-)&lt;2.6(3.1)×10-9 and B(Bs0→pμ-)&lt;12.1(14.0)×10-9, respectively, at 90% (95%) confidence level. These are the first limits on these decays to date

Real-time data processing in the ALICE High Level Trigger at the LHC

At the Large Hadron Collider at CERN in Geneva, Switzerland, atomic nuclei are collided at ultra-relativistic energies. Many final-state particles are produced in each collision and their properties are measured by the ALICE detector. The detector signals induced by the produced particles are digitized leading to data rates that are in excess of 48GB/s. The ALICE High Level Trigger (HLT) system pioneered the use of FPGA- and GPU-based algorithms to reconstruct charged-particle trajectories and reduce the data size in real time. The results of the reconstruction of the collision events, available online, are used for high level data quality and detector-performance monitoring and real-time time-dependent detector calibration. The online data compression techniques developed and used in the ALICE HLT have more than quadrupled the amount of data that can be stored for offline event processing