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2016-04-29
10:55
Geant4 hadronic and electromagnetic validation tests in LHCb
Reference: Poster-2016-534
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Griffith, Peter Noel

LHCb uses Geant4 to simulate the interactions of particles with the detector material and components. The simulation response can vary significantly due to modification of material description, of detector geometry, or of the Geant4 toolkit itself. Therefore, an extensive variety of tools have been developed to study the effects of Geant4 modification on the LHCb simulation framework and on stand-alone environments within the LHCb software infrastructure. These tools have proven to be very effective for investigating new and alternative models provided by Geant4, and also in identifying and fixing anomalous behaviours that arise from changes. The next goal is to have these validation tests run autonomously and periodically, alerting the relevant users when problems are detected. Quick and easy comparison of the results from different software versions and simulation models will be made possible through the web interface of the LHCb Performance and Regression testing system, LHCbPR.

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LHC Students poster session
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2016-04-29
10:51
Novel Real-time Calibration and Alignment Procedure for LHCb Run II
Reference: Poster-2016-533
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Prouve, Claire

In order to achieve optimal detector performance the LHCb experiment has introduced a novel real-time detector alignment and calibration strategy for Run II of the LHC. For the alignment tasks, data is collected and processed at the beginning of each fill while the calibrations are performed for each run. This real time alignment and calibration allows the same constants being used in both the online and offline reconstruction, thus improving the correlation between triggered and offline selected events. Additionally the newly computed alignment and calibration constants can be instantly used in the trigger, making it more efficient. The online alignment and calibration of the RICH detectors also enable the use of hadronic particle identification in the trigger. The computing time constraints are met through the use of a new dedicated framework using the multi-core farm infrastructure for the LHCb trigger. An overview of all alignment and calibration tasks is presented and their performance is shown.

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LHC Students poster session
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2016-04-29
10:41
Bs semileptonic asymmetry at LHCb
Reference: Poster-2016-532
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Dufour, Laurent

pending

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LHC Students poster session
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2016-03-29
10:51
$B0 \to Ds^{(*)}Ds^{(*)}$ and outlook of $B0 \to D^{(*)}D$ at LHCb
Reference: Poster-2016-531
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Belloli, Nicoletta

The measurement of the inclusive branching fraction of $B0s \to Ds^{(*)+} Ds^{(*)-}$ decay together with its contribution to the determination of $\Delta \Gamma{s}/ \Gamma {s}$ are presented. The branching fraction value is compatible with results from previous experiments, improving the world average. The $B0 \to D^+D^-$ and $B0 \to D^*D^{(*)}$ decays are used to measure the parameters associated with $CP$ Violation in those channels; while the analysis associated to the second channel is at an initial stage the first one is almost concluded, the values obtained for the sensitivity on the $CP$ observables show that LHCb can rival the results obtained by previous experiments.

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Conference - LHC students poster session
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2016-03-29
10:13
Prospects for |V$_{ub}$| measurements at LHCb
Reference: Poster-2016-530
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Stefkova, Slavomira

Precise measurements of the quark coupling strength, $|V_{ub}|$, the least well known CKM element, allow a strong test of the unitarity of the CKM matrix. Previous measurements using exclusive and inclusive methods have resulted in values of $|V_{ub}|$ which are 3$\sigma$ apart. The first measurement of $|V_{ub}|$ at LHCb confirmed this tension using the $\Lambda^{0}_{b} \rightarrow p \mu^{-} \overline{\nu}$ decay. This strengthens the motivation to measure this quantity using different channels, one of them being purely leptonic decay $B^{+} \rightarrow \mu^{+} \mu^{-} \mu^{+} \nu$, which benefits from LHCb's very good muon identification ability. This mode had never been observed before. With recent lattice QCD calculations, LHCb can also constrain $|V_{ub}|$ using the $B^{0}_s \rightarrow K^{+} \mu^{-} \overline{\nu}$ decay where the theoretical uncertainty is significantly smaller.

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Conference - LHC students poster session
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2016-03-22
13:59
LHCb measurements of $J/\psi$, and open charm cross-sections at $\sqrt{s}=13$TeV
Reference: Poster-2016-529
Created: 2016. -1 p
Creator(s): Muller, Dominik; Komarov, Ilya

Prompt $J/\psi$, $J/\psi$ from $b$-hadrons and prompt charm meson production is studied in proton-proton collisions at a center-of-mass energy of $\sqrt{s}=13$TeV at the LHCb detector with first application of a novel data streaming technique (Turbo steam). Cross-section measurements are performed as a function of the transverse momentum $p_T$ and the rapidity $y$ of the mesons in the region $p_T<15$GeV$/c$ and $2.0<y<4.5$. Obtained results were compared with expectations from QCD calculations. The ratios of the cross-sections with respect to Run 1 measurements are also determined. Comparison of the measured ratios values with theoretical predictions provided a new sensitive test of the QCD calculations.

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LHCb Poster
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2016-03-18
15:46
Soft QCD and pA physics, with a focus on the ridge at LHCb
Reference: Poster-2016-528
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Dreimanis, Karlis

The LHCb experiment is a forward spectrometer originally designed for study of b and c hadron decays. However, it can be used in a much wider spectrum of physics analyses. The poster presented here highlights a few studies from the extensive range of soft QCD and heavy-ion physics analyses performed at the LHCb. A particular emphasis is placed on the observation of the two-particle angular correlations, so-called ridge effect, in the forward region. The results presented here serve as one of numerous examples of LHCb being a proven multi-purpose detector in the forward region.

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LCHb poster
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2016-03-16
14:23
LHCb New algorithms for Flavour Tagging at the LHCb experiment
Reference: Poster-2016-527
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Fazzini, Davide

The Flavour Tagging technique allows to identify the B initial flavour, required in the measurements of flavour oscillations and time-dependent CP asymmetries in neutral B meson systems. The identification performances at LHCb are further enhanced thanks to the contribution of new algorithms.

Related links:
Conference 125th LHCC Meeting
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2016-03-09
17:06
Measurement of the ${B^0_s \to \phi \phi}$ branching fraction and angular analysis of ${B^0_{(s)} \to \phi \pi^{+}\pi^{-}}$.
Reference: Poster-2016-526
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Morris, Adam

Using 3~fb$^{-1}$ of $pp$ collisions collected by the LHCb detector at $\sqrt{s} = 7$ and 8~TeV, the $B_s^0 \to \phi \phi$ branching fraction is measured to be \[ \mathcal{B}(B^0_s \to \phi \phi) = \left[ 1.84 \pm 0.05 (\mathrm{stat}) \pm 0.07 (\mathrm{syst}) \pm 0.11 (f_s/f_d) \pm 0.12 (\mathrm{norm}) \right] \times 10^{-5}. \] A search for the decay $B^0 \to \phi \phi$ is also made. No signal is observed, and an upper limit on the branching fraction is set as \[ \mathcal{B}(B^0 \to \phi \phi) < 2.8 \times 10^{-8}. \] The rare decays $B_s^0 \to \phi \pi^+ \pi^-$ and $B^0 \to \phi \pi^+ \pi^-$ are observed for the first time. The branching fractions in the range $400<m(\pi^+ \pi^-)<1600$~MeV/$c^{2}$ are measured to be \[ \mathcal{B}(B_s^0 \to \phi \pi^+ \pi^-) = \left[ 3.37 \pm 0.20 (\mathrm{stat}) \pm 0.16 (\mathrm{syst}) \pm 0.34 (\mathrm{norm}) \right] \times 10^{-6} \] \[\mathcal{B}(B^0 \to \phi \pi^+ \pi^-) = \left[ 1.58 \pm 0.18 (\mathrm{stat}) \pm 0.35 (\mathrm{syst}) \pm 0.13 (\mathrm{norm}) \right] \times 10^{-7}. \] An amplitude fit is performed to extract the following exclusive branching fractions: \[ \mathcal{B}(B_s^0 \to \phi f_0(980) \to \phi \pi^+ \pi^-) = \left[ 1.12 \pm 0.16 (\mathrm{stat}) ^{+0.07}_{-0.14} (\mathrm{syst}) \pm 0.11 (\mathrm{norm}) \right] \times 10^{-6} \] \[ \mathcal{B}(B_s^0 \to \phi f_2(1270) \to \phi \pi^+ \pi^-) = \left[ 0.55 \pm 0.10 (\mathrm{stat}) ^{+0.18}_{-0.05} (\mathrm{syst}) \pm 0.06 (\mathrm{norm}) \right] \times 10^{-6}. \] Evidence is found for the decay $B_s^0 \to \phi \rho^0$. An upper limit on the branching fraction is set as \[ \mathcal{B}(B_s^0 \to \phi \rho^0) < 4 \times 10^{-7}. \]

Related links:
LHCb poster
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2016-03-08
15:35
Jet Flavour Tagging and Top Production at LHCb
Reference: Poster-2016-525
Created: 2016. -1 p
Creator(s): Khurewathanakul, Chitsanu

Top quark production in the forward region in proton-proton collisions is observed for the first time. The $W+b$ final state with $W\rightarrow \mu\nu$ is reconstructed using muons with a transverse momentum, $p_{\rm T}$, larger than 25 GeV in the pseudorapidity range $2.0 < \eta < 4.5$. The $b$ jets are required to have $50 < p_{\rm T} < 100$ GeV and $2.2 < \eta < 4.2$, while the transverse component of the sum of the muon and $b{-}$jet momenta must satisfy $p_{\rm T} > 20$ GeV. The algorithm was developed to select $b{-}$ and $c{-}$quark jets. The efficiency for identification a $b(c)$ jet is about 65% (25%) with a probability for misidentifying a light-parton jet of 0.3% for jets with $p_{\rm T} > 20$ GeV. The results are based on data corresponding to integrated luminosity of 1.0 and 2.0 fb$^{-1}$ collected at the center-of-mass energies of 7 and 8 TeV by LHCb. The inclusive top quark production cross-sections in the fiducial region are \begin{align*} \sigma\text{(top)[7 TeV]} \;=\; 239 \pm 53 \;\text{(stat)} \pm 33 \;\text{(syst)} \pm 24 \;\text{(theory) fb},\\ \sigma\text{(top)[8 TeV]} \;=\; 289 \pm 43 \;\text{(stat)} \pm 40 \;\text{(syst)} \pm 29 \;\text{(theory) fb}. \end{align*} These results, along with the observed differential yields and charge asymmetries, are in agreement with next-to-leading order Standard Model predictions.

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