20–25 May 2019
Other Institutes
America/Mexico_City timezone
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Large-area scintillator detector of the Fast Interaction Trigger for the ALICE Experiment.

Not scheduled
1h 30m
Convenciones (CCU)

Convenciones

CCU

Poster Upgrade Poster session

Speaker

Dr Varlen Grabski (Instituto de Fisica UNAM)

Description

During the ongoing Long Shutdown 2 the accelerator complex at CERN will significantly improve
the performance of the collider by boosting the heavy-ion collision parameters of Run 3 and 4 to well beyond the specifications of the current ALICE setup. For instance, the Pb-Pb instantaneous luminosity during Run 3 will increase by a factor of 5 to 6 and the minimum-bias (MB) Pb-Pb interaction rate will reach ~50 kHz, which is ~50 times more than the rate recorded by ALICE with heavy-ion collisions during Run 2. In order to remain operational during the Run 3 and Run 4 ALICE has to upgrade many of its subsystems or replace them with new solutions [1] including the new Fast Interaction Trigger (FIT) [2]. The main online functionalities of FIT will be luminosity monitoring with a direct link to the LHC and the generation of a fast trigger signal for ALICE subsystems. The trigger generated by FIT will allow for online vertex determination, minimum bias and centrality-based event selection, suppression of beam-gas events, and a veto for ultra-peripheral collisions. FIT is a hybrid detector composed of two Cherenkov detector arrays (T0+) and a large sectored scintillator ring (V0+). Due to the limited space, the V0+ scintillator disk will be located only on one side of the interaction point. Nevertheless, because of its large acceptance, V0+ will significantly improve determination of the centrality and the event plane.

The 1.5m diameter plastic scintillator disc of V0+ will be divided into 40 optically-separated cells, each grouped into eight 45o sectors and subdivided into 5 radial segments. The size of the radial segments follows equal steps in pseudo-rapidity coverage. The light from the scintillator will be collected by a matrix of clear, equal-length optical fibers coupled perpendicularly to the surface of the scintillator. At the other end the fibers will be grouped into bundles and read out by Hamamatsu H6614-70 fine-mesh PMTs. This light collecting scheme is characterized by high efficiency, uniform across the entire surface of the scintillator, single-MIP time resolution of around 150-300 ps, and the ability to cope with the required high dynamic range of 1-600 MIP. This presentation will focus on the design of the V0+ and on the outcome of the test results obtained with various prototypes including a full-size 45o section of the actual detector. These measurements were carried out using secondary beams from the CERN-PS accelerator.

We acknowledge the support from DGAPA-UNAM PAPIIT IN111117 and CONACYT 280362 grants.

[1] Upgrade of the ALICE Experiment: Letter of Intent, J.Phys. G41 (2014), 087001
[2] W.H. Trzaska, New Fast Interaction Trigger for ALICE, Nucl. Instrum. Meth. A 845 (2017) 463

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