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2017-02-27
15:51
The new strategy for particle identification samples in Run 2 at LHCb
Reference: Poster-2017-576
Created: 2017. -1 p
Creator(s): Mathad, Abhijit

For Run 2 of LHCb data taking, the selection of PID calibration samples is implemented in the high level trigger. A further processing is needed to provide background-subtracted samples to determine the PID performance, or to develop new algorithms for the evaluation of the detector performance in upgrade scenarios. This is achieved through a centralised production which makes efficient use of LHCb computing resources. This poster presents the major steps of the implementation.

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LHCC Poster Session
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2017-02-27
15:44
Measurement of $b-$hadron production asymmetries in 7 and 8 TeV $pp$ collisions at LHCb
Reference: Poster-2017-575
Created: 2017. -1 p
Creator(s): Ferrari, Fabio

The $B^0$, $B^0_s$, $B^+$ and $\Lambda^0_b$ hadron production asymmetries are measured using a data sample corresponding to an integrated luminosity of 3.0 fb$^{-1}$, collected by the LHCb experiment in proton-proton collisions at centre-of-mass energies of 7 and 8 TeV. The measurements are performed as a function of transverse momentum and rapidity of the $b$ hadrons within the LHCb detector acceptance. The overall production asymmetries, integrated over transverse momentum and rapidity, are also determined.

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LHCC Poster Session
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2017-02-27
15:33
Observation of the decay $B^0_s \to \eta_c \phi$ and evidence for $B^0_s \to \eta_c \pi^+ \pi^- $ at LHCb
Reference: Poster-2017-574
Created: 2017. -1 p
Creator(s): Martin, Morgan Leni

A study of $B^0_s \to \eta_c \phi$ and $B^0_s \to \eta_c \pi^+ \pi^-$ decays is performed using $pp$ collision data corresponding to an integrated luminosity of 3.0 fb, collected with the LHCb detector in Run 1 of the LHC. The observation of the decay $B^0_s \to \eta_c \phi$ is reported, where the $\eta_c$ meson is reconstructed in the $p\bar p$, $K^+K^-\pi^+\pi^-$, $\pi^+\pi^-\pi^+\pi^-$ and $K^+K^-K^+K^-$ decay modes and the $\phi(1020)$ in the $K^+ K^-$ decay mode. The decay $B^0_s \to J/\psi \phi$ is used as a normalisation channel. Evidence is also reported for the decay $B^0_s \to \eta_c \pi^+\pi^-$, where the $\eta_c$ meson is reconstructed in the $p\bar p$ decay mode, using the decay $B^0_s \to J/\psi \pi^+ \pi^-$ as a normalisation channel. The measured branching fractions are \begin{eqnarray*} {\mathcal B (B^{0}_{s} \to \eta_{c} \phi)} &=& \left(5.01 \pm 0.53 \pm 0.27 \pm 0.63 \right) \times 10^{-4} \,, \nonumber \\ {\mathcal B (B^{0}_{s} \to \eta_{c} \pi^+ \pi^-)} &=& \left(1.76 \pm 0.59 \pm 0.12 \pm 0.29 \right) \times 10^{-4} \,, \end{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.

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LHCC Poster Session
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2017-02-27
14:58
Measurement of the photon polarization in radiative $B^0_s$ decays at LHCb
Reference: Poster-2017-573
Created: 2017. -1 p
Creator(s): Sanchez Mayordomo, Carlos

The photon polarization is studied for the first time in $B_s^0$ decays, using an integrated luminosity of 3 fb$^{-1}$ of proton-proton data recorded by the LHCb experiment. An untagged time-dependent analysis of $B_s^0 \rightarrow \phi\gamma$ decays allows to measure the CPV parameter $\mathcal{A}^{\Delta}$, which is sensitive to the left- and right-handed helicity amplitudes. The measured value $\mathcal{A}^{\Delta} = -0.98 \; ^{+0.46}_{-0.52}\text{(stat.)} ^{+0.23}_{-0.20}\text{(syst.)}$ is consistent with the Standard Model prediction within two standard deviations. This value can put constraints on the Wilson coefficients $\mathcal{C}_7$ and $\mathcal{C}_7^{'}$. With a tagged analysis of the same decay the parameter $S_{\phi\gamma}$, also sensitive to the photon polarization, could be measured.

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LHCC Poster Session
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2017-02-27
14:53
Search for $C\!P$ violation in $\Lambda^0_b \to p K^- \mu^+ \mu^-$ decays at LHCb
Reference: Poster-2017-572
Created: 2017. -1 p
Creator(s): Marangotto, Daniele

A search for $C\!P$ violation in the rare decay $\Lambda^0_b \to p K^- \mu^+ \mu^-$ is presented. This decay is mediated by flavour-changing neutral-current transitions in the Standard Model and is potentially sensitive to new sources of $C\!P$ violation. The study is based on a data sample of proton-proton collisions recorded with the LHCb experiment, corresponding to an integrated luminosity of $3\mathrm{fb}^{-1}$. Two observables that are sensitive to different manifestations of $C\!P$ violation are measured, $\Delta\mathcal{A}_{C\!P} \equiv \mathcal{A}_{C\!P}(\Lambda^0_b \to p K^- \mu^+ \mu^-)-\mathcal{A}_{C\!P}(\Lambda^0_b\to pK^- J/\psi)$ and $a_{C\!P}^{\widehat{T}_{\mathrm{odd}}}$, where the latter is based on asymmetries in the angle between the $\mu^+\mu^-$ and $p K^-$ decay planes. No evidence for $C\!P$ violation is found.

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LHCC Poster Session
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2017-02-27
14:47
$CP$-violating lifetime asymmetries of prompt two-body charm decays at LHCb
Reference: Poster-2017-571
Created: 2017. -1 p
Creator(s): Maguire, Kevin Scott

Asymmetries in the time-dependent rates of ${D}^{0} \rightarrow {K}^{+} {K}^{-}$ and ${D}^{0} \rightarrow \mathrm{\pi}^{+} \mathrm{\pi}^{-}$ decays are measured in a $pp$ collision data sample collected by the $\mbox{LHCb}$ detector during $\mbox{LHC}$ Run 1, corresponding to an integrated luminosity of $3{\,fb}^{-1}$. The asymmetries in effective decay widths between ${D}^{0}$ and ${\kern 0.2em\overline{\kern -0.2em D}{}}{}^{0}$ decays, sensitive to indirect $CP$ violation, are measured to be $A_{\Gamma} ({K}^{+} {K}^{-}) = (-0.30 \pm 0.32 \pm 0.10)\times 10^{-3}$ and $A_{\Gamma}(\mathrm{\pi}^{+} \mathrm{\pi}^{-}) = (0.46 \pm 0.58 \pm 0.12)\times 10^{-3}$, where the first uncertainty is statistical, and the second systematic. These measurements show no evidence of CP violation and improve on the precision of the previous best measurements by nearly a factor of two.

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LHCC poster session
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2017-02-27
12:28
LHCb cross-section measurements with heavy flavour jets
Reference: Poster-2017-570
Created: 2017. -1 p
Creator(s): Michielin, Emanuele

Cross-section measurements of jets originating from the hadronization of beauty ($b$) and charm ($c$) quarks at LHCb give the unique opportunity to probe Parton Distribution Functions (PDFs) at low and large momentum fraction and to test the Standard Model in the forward region. In this poster the production of $t\bar{t}$ pairs in the forward region, the measurement of the $W+b\bar{b}$ and $W+c\bar{c}$ cross-section and the measurement of the $Z\rightarrow b\bar{b}$ cross-section are presented.

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LHCC Poster Session
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2017-02-24
11:44
Space Charge Modules for PyHEADTAIL
Reference: Poster-2017-569
Keywords:  Beam dynamics, Numerical simulation, Collective effects, PyHEADTAIL
Created: 2016. -6 p
Creator(s): Oeftiger, Adrian; Hegglin, Stefan Eduard

PyHEADTAIL is a 6D tracking tool developed at CERN to simulate collective effects. We present recent developments of the direct space charge (SC) suite, which is available for both the CPU and GPU. A new 3D particle-in-cell solver with open boundary conditions has been implemented. For the transverse plane, there is a semi-analytical Bassetti-Erskine model as well as 2D self-consistent particle-in-cell solvers with both open and closed boundary conditions. For the longitudinal plane, PyHEADTAIL offers line density derivative models. Simulations with these models are benchmarked with experiments at the injection plateau of CERN’s SPS.

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HB2016
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2017-02-24
11:39
Space Charge Mitigation With Longitudinally Hollow Bunches
Reference: Poster-2017-568
Keywords:  Beam dynamics, radio-frequency, longitudinal emittance blow-up, tune shift, PS
Created: 2016. -6 p
Creator(s): Oeftiger, Adrian; Hancock, Steven; Rumolo, Giovanni

Hollow longitudinal phase space distributions have a flat profile and hence reduce the impact of transverse space charge. Dipolar parametric excitation with the phase loop feedback systems provides such hollow distributions under reproducible conditions. We present a procedure to create hollow bunches during the acceleration ramp of CERN’s PS Booster machine with minimal changes to the operational cycle. The improvements during the injection plateau of the downstream Proton Synchrotron are assessed in comparison to standard parabolic bunches.

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HB2016
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2017-01-25
10:50
ALICE detector schematic after LS2
Reference: Poster-2017-567
Keywords:  ALICE  LS2
Original source: ALICE2017
Created: 2017. -1 p
Creator(s): Tauro, Arturo

ALICE detector schematic after LS2

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ALICE DETECTOR
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