The LHCb simulation application, Gauss, is based on the Gaudi framework and on experiment basic components such as the Event Model and Detector Description. Gauss also depends on external libraries ...for the generation of the primary events (PYTHIA 6, EvtGen, etc.) and on GEANT4 for particle transport in the experimental setup. The application supports the production of different types of events from minimum bias to B physics signals and particle guns. It is used for purely generator-level studies as well as full simulations. Gauss is used both directly by users and in massive central productions on the grid. The design and implementation of the application and its evolution due to evolving requirements will be described as in the case of the recently adopted Python-based configuration or the possibility of taking into account detectors conditions via a Simulation Conditions database. The challenge of supporting at the same time the flexibililty needed for the different tasks for which it is used, from evaluation of physics reach to background modeling, together with the stability and reliabilty of the code will also be described.
The LHCb simulation application, Gauss, consists of two independent phases, the generation of the primary event and the tracking of particles produced in the experimental setup. For the LHCb ...experimental program it is particularly important to model B meson decays: the EvtGen code developed in CLEO and BABAR has been chosen and customized for non-coherent B production as occuring in pp collisions at the LHC. The initial proton-proton collision is provided by a different generator engine, currently PYTHIA 6 for massive production of signal and generic pp collisions events. Beam gas events, background events originating from proton halo, cosmics and calibration events for different detectors can be generated in addition to pp collisions. Different generator packages as available in the physics community or specifically developed in LHCb are used for the different purposes. Running conditions affecting the generated events such as the size of the luminous region, the number of collisions occuring in a bunch crossing and the number of spill-over events from neighbouring bunches are modeled via dedicated algorithms appropriately configured. The design of the generator phase of Gauss will be described: a modular structure with well defined interfaces specific to the various tasks, e.g. pp collisions, particle decays, selections, etc. has been chosen. Different implementations are available for the various tasks allowing selecting and combining them as most appropriate at run time as in the case of PYTHIA 6 for pp collisions or HIJING for beam gas. The advantages of such structure, allowing for example to adopt transparently new generators packages, will be discussed.
A
bstract
In this paper we discuss the possibility of measuring the anomalous magnetic and electric dipole moments of the
τ
lepton. The method consists in studying the spin precession induced by the ...strong effective magnetic field inside channels of a bent crystal with a dedicated setup at the CERN Large Hadron Collider.
This report reviews the study of open heavy-flavour and quarkonium production in high-energy hadronic collisions, as tools to investigate fundamental aspects of Quantum Chromodynamics, from the ...proton and nucleus structure at high energy to deconfinement and the properties of the Quark–Gluon Plasma. Emphasis is given to the lessons learnt from LHC Run 1 results, which are reviewed in a global picture with the results from SPS and RHIC at lower energies, as well as to the questions to be addressed in the future. The report covers heavy flavour and quarkonium production in proton–proton, proton–nucleus and nucleus–nucleus collisions. This includes discussion of the effects of hot and cold strongly interacting matter, quarkonium photoproduction in nucleus–nucleus collisions and perspectives on the study of heavy flavour and quarkonium with upgrades of existing experiments and new experiments. The report results from the activity of the SaporeGravis network of the I3 Hadron Physics programme of the European Union 7
th
Framework Programme.
A golden age for heavy-quarkonium physics dawned a decade ago, initiated by the confluence of exciting advances in quantum chromodynamics (QCD) and an explosion of related experimental activity. The ...early years of this period were chronicled in the Quarkonium Working Group (QWG) CERN Yellow Report (YR) in 2004, which presented a comprehensive review of the status of the field at that time and provided specific recommendations for further progress. However, the broad spectrum of subsequent breakthroughs, surprises, and continuing puzzles could only be partially anticipated. Since the release of the YR, the BESII program concluded only to give birth to BESIII; the
B
-factories and CLEO-c flourished; quarkonium production and polarization measurements at HERA and the Tevatron matured; and heavy-ion collisions at RHIC have opened a window on the deconfinement regime. All these experiments leave legacies of quality, precision, and unsolved mysteries for quarkonium physics, and therefore beg for continuing investigations at BESIII, the LHC, RHIC, FAIR, the Super Flavor and/or Tau–Charm factories, JLab, the ILC, and beyond. The list of newly found conventional states expanded to include
h
c
(1
P
),
χ
c
2
(2
P
),
, and
η
b
(1
S
). In addition, the unexpected and still-fascinating
X
(3872) has been joined by more than a dozen other charmonium- and bottomonium-like “
XYZ
” states that appear to lie outside the quark model. Many of these still need experimental confirmation. The plethora of new states unleashed a flood of theoretical investigations into new forms of matter such as quark–gluon hybrids, mesonic molecules, and tetraquarks. Measurements of the spectroscopy, decays, production, and in-medium behavior of
,
, and
bound states have been shown to validate some theoretical approaches to QCD and highlight lack of quantitative success for others. Lattice QCD has grown from a tool with computational possibilities to an industrial-strength effort now dependent more on insight and innovation than pure computational power. New effective field theories for the description of quarkonium in different regimes have been developed and brought to a high degree of sophistication, thus enabling precise and solid theoretical predictions. Many expected decays and transitions have either been measured with precision or for the first time, but the confusing patterns of decays, both above and below open-flavor thresholds, endure and have deepened. The intriguing details of quarkonium suppression in heavy-ion collisions that have emerged from RHIC have elevated the importance of separating hot- and cold-nuclear-matter effects in quark–gluon plasma studies. This review systematically addresses all these matters and concludes by prioritizing directions for ongoing and future efforts.
A
bstract
In this paper we revisit the idea of measuring the magnetic dipole moments of the charm baryons and, in particular, of
Λ
c
+
by studying the spin precession induced by the strong effective ...magnetic field inside the channels of a bent crystal. We present a detailed sensitivity study showing the feasibility of such an experiment at the LHC in the coming years.
In this paper, we discuss the theoretical framework and the experimental measurements of the magnetic moment of the charmed baryons. We first review the theoretical predictions of the
Λ
c
+
magnetic ...moment and show that the measurements of the magnetic moments of other charmed baryons, such as
Ξ
c
, allow to perform detailed spectroscopy studies. The magnetic moment of the charm quark can be determined using radiative charmonium decay, which can be compared to the
Λ
c
+
magnetic moment within theoretical models. The present results show a tension with majority of theoretical predictions. The magnetic moment of the charmed baryons could potentially be measured directly, using bent-crystal experiments at LHC. The possibility to measure precisely the magnetic moments of charmed baryons needs precise measurement of their polarisation and weak decay parameters. In this paper, we revisit the formalism of the angular analysis needed for these measurements and make a detailed evaluation of initial polarisation of deflected
Λ
c
baryons as a function of crystal orientation. We found a special orientation of the crystal that gives the opportunity to measure the
Λ
c
dimensionless electric dipole moment almost with the same precision as its
g
-factor, which is more than an order of magnitude more efficient than suggested before.
We review the context, the motivations and the expected performances of a comprehensive and ambitious fixed-target programme using the multi-TeV proton and ion LHC beams. We also provide a detailed ...account of the different possible technical implementations ranging from an internal wire target to a full dedicated beam line extracted with a bent crystal. The possibilities offered by the use of the ALICE and LHCb detectors in the fixed-target mode are also reviewed.
The immunoglobulin heavy-chain variable region gene (IgHV) mutational status is considered the gold standard of prognostication in chronic lymphocytic leukemia (CLL) and is currently determined by ...Sanger sequencing that allows the analysis of the major clone. Using next-generation sequencing (NGS), we sequenced the IgHV gene from two independent cohorts: (A) 270 consecutive patient samples obtained at diagnosis and (B) 227 patients from the UK ARCTIC-AdMIRe clinical trials. Using complementary DNA from purified CD19+CD5+ cells, we demonstrate the presence of multiple rearrangements in independent experiments and showed that 24.4% of CLL patients express multiple productive clonally unrelated IgHV rearrangements. On the basis of IgHV-NGS subclonal profiles, we defined five different categories: patients with (a) multiple hypermutated (M) clones, (b) 1 M clone, (c) a mix of M-unmutated (UM) clones, (d) 1 UM clone and (e) multiple UM clones. In population A, IgHV-NGS classification stratified patients into five different subgroups with median treatment-free survival (TFS) of >280(a), 131(b), 94(c), 29(d), 15(e) months (P<0.0001) and a median OS of >397(a), 292(b), 196(c), 137(d) and 100(e) months (P<0.0001). In population B, the poor prognosis of multiple UM patients was confirmed with a median TFS of 2 months (P=0.0038). In conclusion, IgHV-NGS highlighted one quarter of CLL patients with multiple productive IgHV subclones and improves disease stratification and raises important questions concerning the pre-leukemic cellular origin of CLL.
Belle II is a new-generation B-factory experiment, dedicated to exploring new physics beyond the standard model of elementary particles in the flavor sector. Belle II started data-taking in April ...2018, using a synchronous data acquisition (DAQ) system based on pipelined trigger flow control. The Belle II DAQ system is designed to handle a 30-kHz trigger rate with approximately 1% of dead time, under the assumption of a raw event size of 1 MB. The DAQ system is reliable, and the overall data-taking efficiency reached 84.2% during the run period of January 2020-June 2020. The current readout system cannot be operated in the terms of ten years from the viewpoint of DAQ maintainability; meanwhile, the readout system is obstructing high-speed data transmission. A solution involving a peripheral component interconnect (PCI)-express-based readout module with high data throughput of up to 100 Gb/s was adopted to upgrade the Belle II DAQ system. We particularly focused on the design of firmware and software based on this new generation of readout board, called PCIe40, with an Altera Arria 10 field-programmable gate array chip. The 48-Gb transceiver (GBT) serial links, PCI-express hard IP-based direct memory access (DMA) architecture, interface of timing and trigger distribution system, and slow control system were designed to integrate with the current Belle II DAQ system. This article describes the performances accomplished during the data readout and slow control tests conducted using a test bench and a demonstration performed using on-site front-end electronics, specifically involving Belle II TOP and KLM subdetectors.
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