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2016-02-04
12:45
VeloPix ASIC for the LHCb VELO Upgrade
Reference: Poster-2016-515
Created: 2015. -1 p
Creator(s): Cid Vidal, Xabier

The LHCb Vertex Detector (VELO) will be upgraded in 2018 along with the other subsystems of LHCb in order to enable full detector readout at 40 MHz. LHCb will run without a hardware trigger and all data will be fed directly to the software triggering algorithms in the CPU farm. The upgraded VELO is a lightweight silicon hybrid pixel detector with 55 um square pixels, operating in vacuum in close proximity to the LHC beams. The readout will be provided by a dedicated front end ASIC, dubbed VeloPix, matched to the LHCb luminosity requirements. VeloPix is a binary pixel chip with a matrix of 256 x 256 pixels, covering an area of 2 cm^2. It is designed in a 130 nm CMOS technology, and is closely related to the Timepix3, from the Medipix family of ASICs. The principal challenge that the chip has to meet is a hit rate of up to 900 Mhits/s/ASIC, resulting in a data rate of more than 16 Gbit/s. Combining pixels into groups of 2x4 super-pixels enables the use of shared logic and a reduction of bandwidth due to combined address and timestamp information. The pixel hits are combined with other simultaneous hits in the same super-pixel, timestamped, and immediately driven off-chip via custom designed 5.12 Gbit/s serialisers. The power consumption of the analog front end is about 5 uW per pixel, and the total power consumption of the ASIC is less than 2 W. An extensive testbeam and lab test campaign is underway in order to characterise prototype upgrade VELO sensors and simultaneously study the performance of the Timepix3 chip in a high track rate environment. These measurements provide valuable input to the VeloPix project. The VeloPix ASIC design is nearing completion and the chip is expected to be submitted in the autumn. The current status of the ASIC design, performance simulations and prototyping will be described, along with recent lab and testbeam results.

Related links:
10th International "Hiroshima" Symposium on the Development and Application of Semiconductor Tracking Detectors; The VeloPix ASIC for the LHCb VELO Upgrade
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2016-01-27
10:36
ALICE Organisation
Reference: Poster-2016-514
Keywords:  ALICE
Created: 2016. -1 p
Creator(s): Gouriou, Nathalie

ALICE is the acronym for A Large Ion Collider Experiment, one of the largest experiments in the world devoted to research in the physics of matter at an infinitely small scale. Hosted at CERN, the European Laboratory for Nuclear Research, this project involves an international collaboration of more than 1400 physicists, engineers and technicians, including about 340 graduate students, from 132 physics institutes in 37 countries across the world.

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2015-10-23
17:21
Measurement of the $B^0_s\to\phi\phi$ branching fraction and search for the decay $B^0\to\phi\phi$
Reference: Poster-2015-513
Keywords:  flavor physics  B physics  branching fraction  experimental results
Created: 2015. -1 p
Creator(s): Morris, Adam

Using a dataset corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV, the $B_s^0 \to \phi \phi$ branching fraction is measured to be \[ \mathcal{B}(B_s^0 \to \phi \phi) = ( 1.84 \pm 0.05 (\text{stat}) \pm 0.07 (\text{syst}) \pm 0.11 (f_s/f_d) \pm 0.12 (\text{norm}) ) \times 10^{-5}, \] where $f_s/f_d$ represents the ratio of the $B_s^0$ to $B^0$ production cross-sections, and the $B^0 \to \phi K^*(892)^0$ decay mode is used for normalization. This is the most precise measurement of this branching fraction to date, representing a factor five reduction in the statistical uncertainty compared with the previous best measurement. 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 \[ \mathcal{B}(B^0 \to \phi \phi) < 2.8 \times 10^{-8} \] at 90% confidence level. This is a factor of seven improvement compared to the previous best limit.

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Conference poster
© CERN Geneva

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2015-10-23
17:14
LHCb- Observation of $J/\psi p$ resonances consitent with pentaquark staes in $\Lambda^0_b \to J/\psi K^-p$ decays
Reference: Poster-2015-512
Keywords:  pentaquark  QCD  LHCb  multiquark
Created: 2015. -1 p
Creator(s): Adeva Andany, Bernardo

The observation of exotic structures in the $J/\psi p$ channel, refered to as pentaquark-charmonium states, in the decay $\Lambda^0_b \rightarrow J/\psi K^- p$, are presented. An amplitude analysis is performed on the three-body final state that reproduces the two-body mass and angular distributions. To obtain a satisfactory fit of the structures seen in the $J/\psi p$ mass spectrum, it is necessary to include two Breit-Wigner amplitudes that each describe a resonant state. The significance of each of these resonances is more than 9 standard deviations. One has a mass of 4380 $\pm$ 8 $\pm$ 29 MeV and a width of 205 $\pm$ 18 $\pm$ 86 MeV, while the second is narrower, with a mass of 4449.8 $\pm$ 1.7 $\pm$ 2.5 MeV and a width of 39 $\pm$ 5 $\pm$ 19. The preferred $J^P$ assignments are of opposite parity, with one state having spin 3/2 and the other 5/2.

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Conference poster
© CERN Geneva

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2015-10-22
12:30
LHCb - First measurements of long-range near-side angular correlations in $\sqrt {^SNN} = 5$ TeV proton-lead collisions in the forward region
Reference: Poster-2015-511
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Yang, Zhenwei

Two-particle angular correlations are studied in proton-lead collisions at a nucleon-nucleon centre-of-mass energy of $\sqrt {^SNN} = 5$ TeV, collected with the LHCb detector at the LHC. The analysis is based on data recorded in two opposing beam configurations, in which either the direction of the proton or that of the lead remnant is analysed. The correlations are measured as a function of relative pseudorapidity, $\Delta \eta$, and relative azimuthal angle, $\Delta \phi$, for events in different classes of event activity and for different bins of particle transverse momentum. In high-activity events a long-range correlation on the near side is observed in the pseudorapidity range $2.0 < \eta < 4.9$. This is the first measurement of a long-range correlation on the near side in proton-lead collisions in the forward region and extends previous observations in the central region. The correlation increases with growing event activity and is found to be more pronounced in the direction of the lead beam. When comparing the proton and lead hemispheres for the same absolute activity the correlation strengths are compatible with each other.

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Conference poster
© CERN Geneva

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2015-10-21
17:26
LHCb - A SciFi production center in NRC KI FOR LHCb upgrade
Reference: Poster-2015-510
Created: 2015. -1 p
Creator(s): Shevchenko, Vladimir

The Scintillating Fiber Tracker, SciFi for short, will be the main new tracking detector in LHCb. It will provide better than 100 µm spatial resolution, and high rate capability and radiation hardness enabling a fast, 40 MHz, trigger rate with a capability to withstand 50 fb$^{-1}$ integrated luminosity, delivered by LHC, without a major performance degradation. The main active element of the tracker is a scintillating fiber ribbon with the SiPM readout. The ribbons consist of 6 layers of the 250 µm scintillating fibers Kuraray SCSF-78MJ, assembled by winding and bound together by the epoxy glue. NRC Kurchatov Institute, Moscow, together with the colleagues from ITEP, CERN, TU of Dortmund and RWTH of Aachen are developing dedicated production centers with the aim to reach by 2016 production rate one ribbon per day per center, necessary to supply more than 1300 fibre ribbons (mats) needed for the new LHCb tracker.

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Conference poster
© CERN Geneva

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2015-10-21
16:58
LHCb - Forward production of $\Upsilon$ mesons in $pp$ collisions at $\sqrt s$ = 7 and 8 TeV
Reference: Poster-2015-509
Created: 2015. -1 p
Creator(s): Artamonov, Alexander

Updated measurement of $\Upsilon$(nS) production cross-sections at $\sqrt s$ = 7 and 8 TeV is reported. The measurement is carried out for the $\Upsilon (1S)$, $\Upsilon (2S)$ and $\Upsilon (3S)$ states produced in pp collisions at the LHCb setup during the 2011 and 2012 data taking runs with integrated luminosities of about 1 and 2 fb$^{-1}$, respectively. Differential cross-sections are measured in the range $p_T$ < 30 GeV/c and $2.0 < y < 4.5$. We confirm large 30% increase in production cross-section between $\sqrt s$= 7 and 8 TeV, observed in earlier analyzes.

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Conference poster
© CERN Geneva

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2015-10-16
14:02
Measurement of the $B^0_s\to\phi\phi$ branching fraction and search for the decay $B^0\to\phi\phi$
Reference: Poster-2015-508
Keywords:  Flavor physics  B physics  branching fraction  experimental results
Created: 2015. -1 p
Creator(s): Morris, Adam

Using a dataset corresponding to an integrated luminosity of 3.0 fb$^{-1}$ collected in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV, the $B_s^0 \to \phi \phi$ branching fraction is measured to be \[ \mathcal{B}(B_s^0 \to \phi \phi) = ( 1.84 \pm 0.05 (\text{stat}) \pm 0.07 (\text{syst}) \pm 0.11 (f_s/f_d) \pm 0.12 (\text{norm}) ) \times 10^{-5}, \] where $f_s/f_d$ represents the ratio of the $B_s^0$ to $B^0$ production cross-sections, and the $B^0 \to \phi K^*(892)^0$ decay mode is used for normalization. This is the most precise measurement of this branching fraction to date, representing a factor five reduction in the statistical uncertainty compared with the previous best measurement. 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 \[ \mathcal{B}(B^0 \to \phi \phi) < 2.8 \times 10^{-8} \] at 90% confidence level. This is a factor of seven improvement compared to the previous best limit.

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Conference poster
© CERN Geneva

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2015-10-12
09:33
Direct Drive and Eddy Current Septa Magnet Designs for CERN’s PSB Extraction at 2 GeV
Reference: Poster-2015-507
Keywords:  direct drive  eddy current  septum  PSB  PS
Created: 2015. -5 p
Creator(s): Szoke, Zsolt; Atanasov, Miroslav Georgiev; Balhan, Bruno; Baud, Cedric; Borburgh, Jan [...]

In the framework of the LIU project, new septa magnets have been designed between CERN’s PS Booster (PSB) extraction and PS injection. The upgraded devices are to deal with the increased beam energy from 1.4 GeV to 2 GeV at extraction of the PSB. The direct drive recombination septa in the PSB transfer line to the PS, the eddy current PS injection septum together with a bumper at injection have been investigated using finite element software. For the recombination magnets an increase in magnet length is sufficient to obtain the required deflection; however, for the PS injection elements a more novel solution is necessary to also achieve increased robustness to extend the expected lifetime of the pulsed device. The injection septum will share the same vacuum vessel with an injection bumper and both magnets will be located adjacent to each other. The new PS injection magnet will be the first septum operated at CERN based on eddy current technology. The magnetic modelling of the devices, the comparison of the performance of the present 1.4 GeV devices with the predictions for the upgraded 2 GeV devices as well as solutions retained to achieve the field requirements are described in this paper.

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2015-09-18
15:47
LHCb's Time-Real Alignment in RunII
Reference: Poster-2015-506
Keywords:  LHCb
Created: 2015. -1 p
Creator(s): Batozskaya, Varvara

LHCb has introduced a novel real-time detector alignment and calibration strategy for LHC Run 2. Data collected at the start of the fill will be processed in a few minutes and used to update the alignment, while the calibration constants will be evaluated for each run. This procedure will improve the quality of the online alignment. Critically, this new real-time alignment and calibration procedure allows identical constants to be used in the online and offline reconstruction, thus improving the correlation between triggered and offline selected events. This offers the opportunity to optimise the event selection in the trigger by applying stronger constraints. The required computing time constraints are met thanks to a new dedicated framework using the multi-core farm infrastructure for the trigger. The motivation for a real-time alignment and calibration of the LHCb detector is discussed from both the operational and physics performance points of view. Specific challenges of this novel configuration are discussed, as well as the working procedures of the framework and its performance.

Related links:
Conference Poster LHCP2015
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