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2018-04-05
09:43
A novel standalone track reconstruction algorithm for the LHCb upgrade
Reference: Poster-2018-623
Created: 2018. -1 p
Creator(s): Quagliani, Renato

During the LHC Run III, starting in 2020, the instantaneous luminosity of LHCb will be increased up to 2×1033 cm−2 s−1, five times larger than in Run II. The LHCb detector will then have to be upgraded in 2019. In fact, a full software event reconstruction will be performed at the full bunch crossing rate by the trigger, in order to profit of the higher instantaneous luminosity provided by the accelerator. In addition, all the tracking devices will be replaced and, in particular, a scintillating fiber tracker (SciFi) will be installed after the magnet, allowing to cope with the higher occupancy. The new running conditions, and the tighter timing constraints in the software trigger, represent a big challenge for the track reconstruction. This talk presents the design and performance of a novel algorithm that has been developed to reconstruct track segments using solely hits from the SciFi. This algorithm is crucial for the reconstruction of tracks originating from long-lived particles such as KS and Λ. The implementation strategy is based on a progressive cleaning of the tracking environment and on an active use of the information from the stereo hits in order to select tracks. It also profit from the definition of an improved track parameterization. When compared to its previous implementation, the new algorithm has significantly higher performances in terms of efficiency, number of fake tracks and timing, allowing to enhance the physics potential and capabilities of the LHCb upgrade.

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2018-04-04
15:34
ReDecay, a method to re-use the underlying events to speed up the simulation in LHCb
Reference: Poster-2018-620
Created: 2017. -1 p
Creator(s): Muller, Dominik; Rama, Matteo

With the steady increase in the precision of flavour physics measurements collected during LHC Run 2, the LHCb experiment requires simulated data samples of ever increasing magnitude to study the detector response in detail. However, relying on an increase of available computing power for the production of simulated events will not suffice to achieve this goal. The simulation of the detector response is the main contribution to the time needed to generate a sample, that scales linearly with the particles multiplicity of the event. Of the dozens of particles present in the simulation only a few, namely those participating in the studied signal decay, are of particular interest, while all remaining ones, the so-called underlying event, mainly affect the resolution and efficiencies of the detector. This talk presents a novel development for the LHCb simulation software which re-uses the underlying event from previously simulated events. This approach achieves an order of magnitude increase in speed and the same precision compared to the nominal simulation.

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2018-03-29
16:12
Сharmonium production using decays to hadronic final states at LHCb
Reference: Poster-2018-619
Created: 2018. -1 p
Creator(s): Usachov, Andrii

Non Relativistic QCD (NRQCD) provides so far the most successful framework to describe the production of the $J^{PC}=1^{--}$ quarkonium states. However, a comprehensive description of the production and polarisation of the $J/\psi$ state at Tevatron and LHC in the complete $p_T$ and rapidity range remains a challenge. The heavy quark spin symmetry yields direct links between the long distance matrix elements describing hadroproduction of different charmonium states. The production of linked charmonium states - $\eta_c$ and $J/\psi$, $\eta_c(2S)$ and $\psi(2S)$, and the three $\chi_c$ states - can thus be described simultaneously. Experimentally the production of non-$1^{--}$ charmonium states can be studied by reconstructing their decays to fully hadronic final states. The LHCb measurement of the $\eta_c(1S)$ prompt production and production in inclusive b-hadron decays via the decay $\eta_c(1S)\to p\bar{p}$ is discussed together with its strong impact on NRQCD-based theory models. Recent LHCb measurement of the $\chi_c$ and $\eta_c(2S)$ states production in inclusive b-hadron decays using their decays to $\phi\phi$ is also presented; the discrepancy with existing theoretical prediction is demonstrated. Prospects of measuring prompt $\eta_c(2S)$ production at the LHCb using 2018 data is discussed.

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2018-03-14
10:41
Il Bosone di Higgs

Reference: Poster-2018-617
Keywords:  ATLAS  Higgs  Poster  Divulgazione  BEM  Meccanismo di Higgs  Meccanismo BEH  A0
Created: 2018. -1 p
Creator(s): Hemmer, Sabine

Poster di ATLAS sul bosone di Higgs indirizzato al pubblico generico, che spiega il meccanismo di Brout-Englert-Higgs e la sua importanza. Spiega anche il ruolo del Bosone di Higgs, come viene cercato, il percorso della sua scoperta e cosa viene dopo la scoperta. Disponibile anche in Francese (http://cds.cern.ch/record/1697501) e Inglese (http://cds.cern.ch/record/1697389). Non esitate a utilizzarlo nelle sedi dei vostri Istituti e negli eventi divulgativi! Il poster è in formato A0. Cliccate sull'immagine per scaricare il .pdf ad alta qualità e stamparlo dove preferite. Per qualisasi domanda o commento potete contattare atlas-outreach-coordination@cern.ch

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2018-03-06
14:44
Time-dependent CP violation in $B^0_{(s)} \to h^+h^-$ decays
Reference: Poster-2018-616
Created: 2018. -1 p
Creator(s): Fazzini, Davide

The direct and mixing-induced CP-violating asymmetries in $B^0 \to \pi^+ \pi^-$ and $B_s \to K^+ K^-$ decays have been measured using a sample of pp collisions collected by the LHCb experiment during the Run1 of the LHC and corresponding to an integrated luminosity of 3.0 fb$^{-1}$.The time-integrated CP asymmetries in $B^0 \to K^+ \pi^-$ and $B_s \to \pi^+ K^-$ decays have also been measured, using the same data sample.The measurements of the CP-violating asymmetries of the $B^0 \to \pi^+ \pi^-$, $B_s \to K^+\pi^-$ and $B_s \to \pi^+K^-$ decays are the most precise from a single experiment. The measurements of the CP-violating asymmetries of the Bs->KK decays are compatible with the previous results from LHCb.

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2018-03-06
14:25
Observation of the decay $B \to p\overline{p}\mu\nu$ and Lepton Flavour Universality with $B \to p\overline{p}\mu\nu$
Reference: Poster-2018-615
Created: 2018. -1 p
Creator(s): Tilley, Matthew James

The first observation of the $B \to p\overline{p}\mu$ decay should be possible at the LHCb experiment with a significance far in excess of 5$\sigma$ . As well as a branching fraction measurement, a precision measurement of the $p\overline{p}$ mass spectrum will be performed. The ratio of branching fractions $\mathcal{B}(B \to p\overline{p}\tau)/\mathcal{B}(B \to p\overline{p}\mu)$ is a test of lepton flavour universality in the Standard Model. This measurement is in progress at LHCb and would be the first test involving a $b\to u\tau\nu$ transition.

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2018-03-02
14:03
Luminosity Measurements at LHCb for Run II
Reference: Poster-2018-614
Created: 2018. -1 p
Creator(s): Coombs, George

A precise measurement of the luminosity is a necessary component of many physics analyses, especially cross-section measurements. At LHCb two different direct measurement methods are used to determine the luminosity: the “van der Meer scan” (VDM) and the “Beam Gas Imaging” (BGI) methods. A combined result from these two methods gave a precision of less than 2% for Run I and efforts are ongoing to provide a similar result for Run II. Fixed target luminosity is determined with an indirect method based on the single electron scattering cross-section.

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2018-03-02
13:59
Measurement of $B_{s}$ using $J/\psi \pi^{+}\pi^{-}$ at LHCb
Reference: Poster-2018-613
Created: 2018. -1 p
Creator(s): Liu, Xuesong

The measurement of violating phase $phi_{s}$ is one of the key goals of the LHCb experiment. It will be performed via a time-dependent amplitude analysis. This poster summaries the measurement of $phi_s$ using $B_{s}\to J/\psi \pi{+}\pi^{-}$ at LHCb using Run-I and years 2015-2016 of Run-II data. The results are compatible with SM predictions.

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2018-03-02
10:39
Angular analysis of $\Lambda_{b} \rightarrow \Lambda \mu^{+}\mu^{-}$
Reference: Poster-2018-612
Created: 2018. -1 p
Creator(s): Chatzikonstantinidis, Georgios

The angular analysis of the rare baryon decay of $\Lambda_{b}\rightarrow \Lambda (\rightarrow p\pi^{-})\mu^{+}\mu^{-}$ in high $q^{2}$ is presented. The dataset that is used corresponds to an integrated luminosity of 5.0 fb$^{-1}$ of pp - collision data collected at centre-of-mass energies between 7 and 13 TeV by the LHCb detector in 2011, 2012, 2015 and 2016. Angular observables are determined using a moment analysis of the angular distribution.

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2018-03-02
10:29
$\Xi_{cc}$ decays and properties
Reference: Poster-2018-611
Created: 2018. -1 p
Creator(s): Traill, Murdo Thomas

The $\Xi$ particles are baryons contains 2 constituent charm quarks in their structure which are expected to decay to high multi-body final states. The LHCb detector is ideally designed for studies of them due to its excellent particle identification and vertex reconstruction. Its capabilities in this area of physics was firmly demonstrated when LHCb announced the discovery of the first ever doubly charmed baryon, $\Xi^{++}_{cc}$, in decays of $\Xi^{++}_{cc} \to \Lambda^+K^-\pi^+\pi^+$ in 2017. This doubly charmed baryon was observed as a highly significant structure in the $\Lambda^+_c K^-\pi^+\pi^+$ mass spectrum from proton-proton collision data recorded by the LHCb detector in Run2. A yield of 313 $\pm$ 33 $\Xi^{++}_{cc}$ candidates is measured and the local significances is in excess of 12 $\sigma$ in the 13 TeV data. The properties of the peak suggest it is inconsistent with being a strongly decaying state. From the 13 TeV data, the mass is measured to be $3621.40\pm 0.72(stat.) \pm 0.27(syst.) \pm 0.14( \Lambda^+_c) MeV/c^2$. More analyses in the doubly charmed baryon sector using LHCb data are now well advanced. This includes, but is not limited to, searches for the singly charged $\Xi^{+}_{cc}$ state as well as the lifetime measurement of the $\Xi^{++}_{cc}$ state.

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