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Ostatnio dodane:
2018-06-19
16:58
A tracking algorithm for the reconstruction of the daughters of long-lived particles in LHCb
Reference: Poster-2018-636
Created: 2018. -1 p
Creator(s): Dendek, Adam Mateusz

A tracking algorithm for the reconstruction of the daughters of long-lived particles in LHCb 5 Jun 2018, 16:00 1h 30m Library, Centro San Domenico () LHC experiments Posters session Speaker Katharina Mueller (Universitaet Zuerich (CH)) Description The LHCb experiment at CERN operates a high precision and robust tracking system to reach its physics goals, including precise measurements of CP-violation phenomena in the heavy flavour quark sector and searches for New Physics beyond the Standard Model. The track reconstruction procedure is performed by a number of algorithms. One of these, PatLongLivedTracking, is optimised to reconstruct "downstream tracks", which are tracks originating from decays outside the LHCb vertex detector of long-lived particles, such as Ks or Λ0. After an overview of the LHCb tracking system, we provide a detailed description of the LHCb downstream track reconstruction algorithm. Its computational intelligence part is described in details, including the adaptation of the employed Machine Learning algorithms to the environment of the real-time high level trigger. The downstream tracking performance, obtained using a simulated data samples, is also presented.

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2018-06-19
16:54
LHCb Particle Identification Strategy and Performance in Run 2
Reference: Poster-2018-635
Created: 2018. -1 p
Creator(s): Tilley, Matthew James

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 calibration samples used for the determination the PID performance, which is achieved through a centralised production that makes highly efficient use of LHCb computing resources. This poster presents the major steps of the production procedure and the charged particle PID performance measured using these calibration samples.

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2018-06-19
16:45
LHCb full-detector real-time alignment and calibration: latest developments and perspective
Reference: Poster-2018-634
Created: 2018. -1 p
Creator(s): Dziurda, Agnieszka; Mogini, Andrea

A key ingredient of the data taking strategy used by the LHCb experiment at CERN in Run 2 is the novel real-time detector alignment and calibration. Data collected at the start of the fill are processed within minutes and used to update the alignment, while the calibration constants are evaluated hourly. This is one of the key elements which allow the reconstruction quality of the software trigger in Run-II to be as good as the offline quality of Run 1. The most recent developments of the real-time alignment and calibration paradigm enable the fully automated updates of the RICH detectors' mirror alignment and a novel calibration of the calorimeter systems. Both evolutions improve the particle identification performance stability resulting in higher purity selections. The latter leads also to an improvement in the energy measurement of neutral particles, resulting in a 15% better mass resolution of radiative b-hadron decays. A large variety of improvements has been explored for the last year of Run 2 data taking and is under development for the LHCb detector upgrade foreseen in 2021.These range from the optimisation of the data samples selection and strategy to the study of a more accurate magnetic field description. Technical and operational aspects as well as performance achievements are presented, focusing on the new developments for both the current and upgraded detector.

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2018-06-13
17:20
Neutral particles identification at LHCb
Reference: Poster-2018-633
Created: 2018. -1 p
Creator(s): Quintana, Boris Julien

Important analyses of the core LHCb physics program rely on calorimetry to identify photons, high-energy neutral pions and electrons. For this purpose, the LHCb calorimeter system is composed of a scintillating pad plane, a preshower detector, an electromagnetic and a hadronic sampling calorimeters. The interaction of a given particle in these detectors leaves a specific signature. This is exploited for particle identification (PID) by combining calorimeters and tracking information into multi-variate classifiers. In this contribution, we focus on the identification of photons against high-energy neutral pion and hadronic backgrounds. Performance on Run 1 data will be shown. Small discrepancies with simulation predictions are then discussed, with special emphasis on the methods to correctly estimate PID cut efficiencies by means of large calibration samples of abundant beauty and charm decays to final states with photons. Finally, the technical aspects of the collection of these samples in Run 2 are presented.

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2018-06-13
17:17
Measurement of track reconstruction efficiency at LHCb
Reference: Poster-2018-632
Created: 2018. -1 p
Creator(s): Van Veghel, Maarten; Dufour, Laurent

The precise evaluation of the tracking efficiencies is a crucial element for many physics analysis, especially those aiming at measuring production cross sections or branching fractions. In the LHCb experiment, several data-driven approaches have been conceived and continuously improved in order to provide a precise evaluation of the tracking efficiencies. They are mostly based on clean samples of muons, but the recent hints of lepton universality violation required the development of robust data-driven techniques specifically dedicated to electrons, in order to reduce the systematic uncertainties. In addition, special data streams have been recently put in place to collect and save the calibration samples selected in the LHCb software trigger for both muons and electrons, ensuring a prompt access right after the data has been collected.

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2018-06-13
17:14
CP violation in $B^0_{(s)} \to h+h−$ decays
Reference: Poster-2018-631
Created: 2018. -1 p
Creator(s): Fazzini, Davide

The time-dependent CPV direct and mixing-induced asymmetries in $B^0 \to \pi^+ \pi^-$ and $B_s \to K^+ K^-$ decays have been measured at the LHCb experiment using data collected during Run1 at centre-of-mass energies of 7 and 8 TeV, corresponding to 3fb$^{-1}$. The data set was also used for a measurement of time-integrated CP asymmetries in $B^0 \to K^+ \pi^-$ and $B_s \to \pi^+ K^-$ decays.The results obtained supersede those of B factories with much higher precision. No other experiment has ever measured CP violation in $B_s \to K^+ K^-$ decays. The measurements of the time-integrated CP asymmetries are the most precise from a single experiment to date.

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2018-06-13
17:06
Anti-deuteron sensitivity studies at LHCb
Reference: Poster-2018-630
Created: 2018. -1 p
Creator(s): Baker, Sophie Katherine

Measurements of anti-deuterons in collider experiments can help to reduce systematic uncertainties in indirect searches for dark matter. Two predominant unknowns in these searches are the production of secondary anti-deuterons in the cosmos from spallation processes, and anti-deuteron production from annihilating dark matter. LHCb is a forward spectrometer on the LHC ring, designed to measure b-hadron decays from high energy proton-proton collisions. With the detector's excellent particle identification capabilities, deuteron and anti-deuteron measurements at LHCb could help to parametrise the two cosmological processes. Recent studies of (anti-)deuteron identification at LHCb and the prospects for measuring prompt (anti-)deuterons from pp-collisions will be presented, as well as a working analysis of b-baryrons decaying to deuterons.

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2018-05-24
10:43
Search for gluon saturation at Bjorken-x $\in [10^{−6}, 10^{−4}]$ with the LHCb detector(ID:39)
Reference: Poster-2018-629
Keywords:  LHCb
Created: 2018. -1 p
Creator(s): Da Silva, Cesar Luiz

A new state of matter, where gluons have overlapping wave functions, has been in the minds of particle and nuclear physicists for decades. This gluon saturated state could explain several recent observations such as particle production and collectivity observed in p+p, p+A and A+A collisions at RHIC and LHC. The LHCb experiment is a forward spectrometer with vertexing, tracking, $p, K, \pi, e, \mu$ identification and calorimetry in the pseudorapidity region 2< $\eta$ <5. LHCb is therefore well suited to study the gluon density of hadrons in at small Bjorken-x values $(x∼10^{−6}−10^{−5})$, down to two orders of magnitude smaller than HERA. The status of the analysis efforts aimed at finding the gluon saturation scale at LHCb using isolated photon yields and their correlations with hadrons and jets will be shown. In addition, the concept and R&D efforts of a new particle tracker inside the LHCb magnet to improve measurements of small Q2 processes, where gluon saturation is expected, will be presented.

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2018-05-17
14:18
Measurement of the time-integrated CP asymmetry in $D^0 \to K_S^0 K_S^0$ decays with LHCb
Reference: Poster-2018-628
Created: 2018. -1 p
Creator(s): Tuci, Giulia

CP violation in charm has not yet been observed, although measurements of time-integrated CP asymmetries in $D^0 \to K^+K^-$ and $D^0 \to \pi^+\pi^- decays$ have reached a remarkable precision, O(0.1%). The $D^0 \to K_S^0 K_S^0$ decay is a promising discovery channel for CP violation in charm. A prediction based on Standard Model gives an upper limit for the CP asymmetry of 1.1% (C.L. 95%). Further enhancements could result from contributions from physics beyond the Standard Model. We present a measurement of the time-integrated CP asymmetry in prompt $D^0 \to K_S^0 K_S^0$ decays, performed using data collected with LHCb experiment in 2015 and 2016 at a 13 TeV pp center-of-mass energy (Run-2). This result improves the sensitivity obtained by LHCb in Run-1.

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2018-04-24
22:15
Betatron-collimation Studies for Heavy Ions in the FCC-hh
Reference: Poster-2018-627
Note: ORCID: 0000-0002-7669-9837
Keywords:  FCC-hh  Heavy Ions  Collimation  Betatron  STIER  Lossmap
Created: 2018. -1 p
Creator(s): Logothetis Agaliotis, Efstathios; Schaumann, Michaela

One of the biggest challenges in the design of the FCC-hh is the collimation system. From LHC experience it is known that a collimation system optimized for proton cleaning has a significantly reduced efficiency for heavy ions. The study presented in this contribution evaluates the betatron-collimation efficiency for the heavy-ion operation with lead nuclei at a beam energy of 50 Z TeV in the system designed for proton operation. The fragmentation processes of the main beam particles in the primary collimator are simulated with FLUKA and fragments are individually tracked with SixTrack until being lost in the downstream aperture. In this way a first-impact loss-map is obtained, identifying locations where high energy deposition are to be expected. This provides a first-level assessment of feasibility and allows to include countermeasures in the conceptual accelerator design.

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FCC week 2018
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