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2016-09-26
15:13
Time-dependent CP-violation measurements in $B^0 \to D^+D^–$ decays at LHCb
Reference: Poster-2016-556
Created: 2016. -1 p
Creator(s): Bel, Lennaert

Overconstraining the unitarity triangle is a key goal of LHCb. The excellent time resolution of the detector lends itself to high precision time dependent CP violation measurements. CP observables in $B^0 \to D^{+}D^{‐}$ decays are of great interest as they have the potential to be sensitive to new physics contributions. There is a long¬‐existing tension between results from BaBar and Belle on $B^0 \to D^{+}D^{‐}$. We present results on these CP observables with the full Run 1 dataset.

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ICHEP 2016
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2016-09-14
10:17
Beam test results for the upgraded LHCb RICH opto-electronic readout system
Reference: Poster-2016-555
Created: 2016. -1 p
Creator(s): Carniti, Paolo

The LHCb experiment is devoted to high-precision measurements of CP violation and search for New Physics by studying the decays of beauty and charmed hadrons produced at the Large Hadron Collider (LHC). Two RICH detectors are currently installed and operating successfully, providing a crucial role in the particle identification system of the LHCb experiment. Starting from 2019, the LHCb experiment will be upgraded to operate at higher luminosity, extending its potential for discovery and study of new phenomena. Both the RICH detectors will be upgraded and the entire opto-electronic system has been redesigned in order to cope with the new specifications, namely higher readout rates, and increased occupancies. The new photodetectors, readout electronics, mechanical assembly and cooling system have reached the final phase of development and their performance was thoroughly and successfully validated during several beam test sessions in 2014 and 2015 at the SPS facility at CERN. Details of the test setup and performance results of the opto-electronic readout system will be presented.

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RICH 2016
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2016-09-13
10:00
High rate tests of the LHCb RICH Upgrade system
Reference: Poster-2016-554
Created: 2016. -1 p
Creator(s): Blago, Michele Piero

One of the biggest challenges for the upgrade of the LHCb RICH detectors from 2020 is to readout the photon detectors at the full 40 MHz rate of the LHC proton-proton collisions. A test facility has been setup at CERN with the purpose to investigate the behaviour of the Multi Anode PMTs, which have been proposed for the upgrade, and their readout electronics at high trigger rates. The MaPMTs are illuminated with a monochromatic laser that can be triggered independently of the readout electronics. A first series of tests, including threshold scans, is performed at low trigger rates (20 kHz) for both the readout and the laser with the purpose to characterise the behaviour of the system under test. Then the trigger rate is increased in two separate steps. First the MaPMTs are exposed to high illumination by triggering the pulsed laser at a high (20 MHz) repetition rate while the DAQ is readout at the same low rate as before. In this way the performance of the MaPMTs and the attached electronics can be evaluated at high laser exposure rate. In the second step both the laser and the DAQ are triggered at the high rate in order to evaluate the full readout chain.

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RICH 2016
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2016-09-12
16:37
LHCb upstream tracker
Reference: Poster-2016-553
Created: 2016. -1 p
Creator(s): Artuso, Marina

The detector for the LHCb upgrade is designed for 40MHz readout, allowing the experiment to run at an instantaneous luminosity of 2x10^33 cm$^2$s$^-1$. The upgrade of the tracker subsystem in front of the dipole magnet, the Upstream Tracker, is crucial for charged track reconstruction and fast trigger decisions based on a tracking algorithm involving also vertex detector information. The detector consists of 4 planes with a total area of about 8.5m$^2$, made of single sided silicon strip sensors read-out by a novel custom-made ASIC (SALT). Details on the performance of prototype sensors, front-end electronics, near-detector electronics and mechanical components are presented.

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ICHEP 2016
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2016-09-12
10:58
IMPROVEMENT OF THE CERN SPS ELECTROSTATIC SEPTA ION TRAPS
Reference: Poster-2016-552
Created: 2016. -4 p
Creator(s): Balhan, Bruno; Borburgh, Jan; Barlow, Roger Andrew; Raffaele, Graziano

At CERN, the SPS synchrotron is equipped with a slow extraction channel towards the fixed target beam lines in the North Area This channel includes five consecutive electrostatic septa, where the field free region and the active high field region are separated by an array of tungsten-rhenium wires. The field-free region provides for the circulating beam, while the high field region is used to deflect the extracted beam. Since the residual gas can be ionized by the orbiting beam, low energy ions could cross the wire array and enter the high field region and cause high voltage breakdown when accelerated onto the cathode. To prevent low energy ions from entering this high electric field region, a vertical field is applied to the orbiting beam using so-called ‘ion traps’ for active protection. The vertical field is created by electrodes placed inside the region containing the circulating beam. Due to electromagnetic coupling onto the ion trap electrodes observed with the high frequency LHC beam (25 ns spaced bunches), the efficiency of the ion traps is greatly reduced. This leads to increased vacuum activity (electron cloud related) as well as high spark rates both in the main field and between the ion trap electrodes and their grounded support. In view of the SPS performance increase required for HL-LHC, this paper highlights the upgrades and improvements required to obtain a stable ion trap field and significantly reduce the number of breakdown events observed with the LHC beam in the accelerator.

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2016-09-06
15:33
The early career, gender, and diversity actions at the LHCb Collaboration
Reference: Poster-2016-551
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Rademacker, Jonas; Sciascia, Barbara

Numerous surveys of modern particle physics indicate that the discipline is still largely a male pursuit, and one in which women and other marginalised groups continue to face discriminatory practices. The fraction of female particle physicists reduces with each career stage. Early career particle physicists face precarious employment conditions with serial short term contracts, long working hours, the frequent need to relocate, and little prospect for a permanent academic position. There are indications that these employment conditions add to the gender-imbalance in the field, but clearly, this problem directly affects both male and female early career scientists. The LHCb experiment has, as the first (and so far only) LHC experiment, created a dedicated office for Early Career Gender and Diversity (ECGD) (see http://lhcb.web.cern.ch/lhcb/ECGD_Office/ECGD-intro.html ). The ECGD office’s role is to to advise the management on ECGD matters; provide a point of contact for anybody experiencing any kind discrimination, bullying or harassment; collate regular statistics and other relevant information related to gender and, where appropriate, other ECGD matters; organise regular open meetings where ECGD matters are discussed. We report on our first year of experiences as the first ECGD officers in the LHC’s first ECGD office. Amongst the pitfalls of such an office is the potential of being perceived as either inconsequential, or as an external body that is a source of new rules and complications. We will highlight the strategies we adopted in an attempt to circumnavigate these pitfalls, aiming to be (and be seen as) an integral part of LHCb, working with the entire collaboration to achieve an environment in which all members can thrive. We will also discuss a few highlights of our programme in that year, including well-attended plenary meetings at LHCb weeks on topics such as “mentoring”, “(m/p)aternity leave”, “sexual harrassment”, “careers inside and outside HEP” - and the implementation of a mentoring scheme.

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ICHEP 2016
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2016-09-05
10:51
LHCb Exotica and Higgs searches
Reference: Poster-2016-550
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Lucchesi, Donatella

The unique phase space coverage and features of the LHCb detector at the LHC makes it an ideal environment to probe complementary New Physics parameter regions. In particular, recently developed jet tagging algorithms are ideal for searches involving $b$ and $c$ jets. This poster will review different jet-related exotica searches together with the efforts in the search for a Higgs boson decaying to a pair of heavy quarks.

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ICHEP 2016
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2016-09-05
10:41
Flavour tagging of $b$ mesons in $pp$ collisions at LHCb
Reference: Poster-2016-549
Keywords:  LHCb
Created: 2016. -1 p
Creator(s): Mueller, Vanessa

Flavour tagging, i.e. the inference of the production flavour of reconstructed $b$ hadrons, is essential for precision measurements of decay time-dependent $CP$ violation and of mixing parameters in the the neutral $B$ meson systems. LHC's $pp$ collisions with their high track multiplicities constitute a challenging environment for flavour tagging and demand for new and improved strategies. We present recent progress and new developments in flavour tagging at the LHCb experiment, which will allow for a further improvement of $CP$ violation measurements in decays of $B^0$ and $B_s^0$ mesons.

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ICHEP 2016
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2016-09-02
11:19
LHCb Run II tracking performance and prospects for the Upgrade
Reference: Poster-2016-548
Created: 2016. -1 p

The LHCb tracking system consists of a Vertex Locator around the interaction point, a tracking station with four layers of silicon strip detectors in front of the magnet, and three tracking stations, using either straw-tubes or silicon strip detectors, behind the magnet. This system allows to reconstruct charged particles with a high efficiency (typically > 95% for particles with momentum > 5 GeV) and an excellent momentum resolution (0.5% for particles with momentum < 20 GeV). The high momentum resolution results in very narrow mass peaks, leading to a very good signal-to-background ratio in such key channels as $B_s\to\mu^+\mu^-$. Furthermore an optimal decay time resolution is an essential element in the studies of time dependent CP violation. For Run II a novel reconstruction strategy was adopted, allowing to run the same track reconstruction in the software trigger as offline. This convergence was possible due to a staged approach in the track reconstruction and a large reduction in the processing time, without any loss in the key performance numbers like impact parameter or decay time resolution. Having a unified track reconstruction greatly benefits all physics analyses due to the perfect alignment between their online and offline selection. In this talk, we will give an overview of the track reconstruction in LHCb, review its performance in Run II of the LHC and highlight the challenges and improvements. A similar scheme is planned to be used in the LHCb upgrade foreseen for 2020. At that time LHCb will run at an instantaneous luminosity of $2×10^{33}$cm$^{-2}$$s^{-1}$ with a fully software based trigger with a read-out of the detector at a rate of 40 MHz. A full new tracking system is being developed: a vertex detector based on silicon pixel sensors, a new silicon micro-strip detector with a high granularity and the scintillating fibre tracker. The new tighter time constraint in the trigger, where only about 13 ms are available per event, combined with a higher luminosity by a factor 5 represent a big challenge for the track reconstruction. A new track finding strategy has been considered and new computing approaches, partly based on GPUs, are under study. We will present the new strategy and the new fast track reconstruction, including the performance and the highlights of the improvements with respect to the current tracking system of LHCb.

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ICHEP 2016
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2016-08-16
11:54
$B^+_c$ meson production, decays and properties at LHCb
Reference: Poster-2016-547
Created: 2016. -1 p
Creator(s): Lusiani, Alberto

We report the first study of the $B_c^+ \to K^+K^-\pi^+$ decay and an update of the measurement of the ratio of branching fractions $R_{K/\pi} \equiv {\cal B}(B_c^+\to J/\psi K^+)/{\cal B}(B_c^+\to J/\psi\pi^+)$. Both results use an integrated luminosity of $3.0fb^{-1}$ collected by the LHCb experiment in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV. We measure $B_c^+ \to \chi_{c0}(\to K^+ K^-)\pi^+$ with $4.0\sigma$ significance and $\frac {\sigma(B_c^+)} {\sigma(B^+)}$ X ${\cal B}(B_c^+ \to \chi_{c0}\pi^+)$ to be $(9.8^{+3.4}_{-3.0}(stat) \pm 0.8(syst))$ X $10^{-6}$. The contribution of $B_c^+ \to K^+K^-\pi^+$ via $\overline{b}c$ weak annihilation for $m(K^-\pi^+) < 1.834 GeV$ is measured with $2.4\sigma$ significance. The ratio of branching fractions $R_{K/\pi} \equiv {\cal B}(B_c^+ \to J/\psi K^+) / {\cal B}(B_c^+ \to J/\psi \pi^+)$ is measured to be $R_{K/\pi} = 0.079 \pm 0.007(stat) \pm 0.003(syst)$. This result significantly improves the previous LHCb measurement.

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ICHEP 2016
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