LHCb
Based at the CERN laboratory near Geneva LHCb is one of the four big detectors of the Large Hadron Collider (LHC), in which proton-proton collisions have been taking place since 2009 (in LHC’s Runs I and II), and which is still expected to continue taking data in the next 15 to 20 years. Located in a vast underground cavern, 100 metres beneath the French countryside, the project involves about 1400 scientists, engineers and technicians from 86 institutions of 18 countries (numbers at January 2021).
LHCb is a forward spectrometer whose acceptance and specific features make it very different and complementary to the rest of the LHC experiments. Its main activities currently involve the study of CP-violation, lepton flavour violation and rare decays.
LHCb, which stands for Large Hadron Collider beauty experiment, was primarily designed to perform accurate measurements of the quark mixing matrix elements, especially the phases between the second and third generations. These are intimately related to the presence of CP-violation in Nature, and could be essential to explain the light asymmetries between matter and antimatter, that explain why our current Universe is composed by the first and not by the second. The experiment also aims to explore heavy meson decays highly suppressed in the Standard Model, such as Bs → μμ. In the last years, LHCb has substantially extended its physics reach with new methodologies of analyses and can nowadays be considered a general purpose LHC detector. Examples of this involve top and EW physics, direct searches for BSM particles or physics of strongly interacting matter at extreme energy densities (in proton-lead or lead-lead collisions).
The unique geometry and versatility of the LHCb detector have proven invaluable for conducting studies in heavy ion physics. The primary objective of this branch of physics is to investigate and characterize strongly interacting matter across a spectrum of energy densities, ranging from small to extreme.
The LHCb detector’s capability to record fixed target collisions (facilitated by injecting gases near the interacting region of the LHCb setup), proton-Lead and LeadLead collisions, is particularly noteworthy and unique at LHC. Within the LHCb-IFT (Ion and Fix Target) group at IGFAE, dedicated efforts are underway to explore proton-Lead collisions. This research aims to gain a deeper understanding of nuclear Parton Distribution Functions, analyze the collective behavior of produced particles, and elucidate the phenomenon of strangeness enhancement.
These analyses hold the key to establishing a robust reference point for characterizing the Quark-Gluon Plasma, a novel state of matter predicted to have existed a few microseconds after the Big Bang. By delving into the intricacies of proton-Lead collisions, the LHCb-IFT group contributes significantly to unraveling the mysteries surrounding this unique phase of the early universe.
LHCb is 21 m long, 10 m high and 13 m wide. IGFAE researchers involved ath the LHCb has undertaken significant responsibility in its construction. In particular, it was in was in charge of the assembly and installation of the Inner Tracker, a device of over 200000 electronics channels that surrounds the LHC beam pipe and provides accurate measurements of the quark decay tracks.
During the 2019-2020 period, the LHCb detector will undergone a full upgrade, that will affect very significantly the physics reach of the experiment. After this upgrade, the detector will be fully readout at 40 MHz and will cope with much higher luminosities, leading to much higher statistics in several key channels. The IGFAE group is currently involved in the upgrade of the Vertex Locator detector, crucial to detect accurately the decay position of B mesons and hadrons. For this upgrade, the technology of the detector will be changed, using pixels instead of strips, which involves a series of important technical challenges.
Another important need to complete the LHCb physics goals is a large amount of computing resources. In particular, IGFAE hosts a 2nd level center (or Tier-2) of the LHCb global computing system. Currently, this center, located in the IGFAE facilities, offers a computing power of approximately 10 kHS06 through 84 servers of various characteristics that provide about 1036 processor cores and contributes to the 6% of the global LHCb needs.