478 research outputs found
Multidifferential study of identified charged hadron distributions in -tagged jets in proton-proton collisions at 13 TeV
Jet fragmentation functions are measured for the first time in proton-proton
collisions for charged pions, kaons, and protons within jets recoiling against
a boson. The charged-hadron distributions are studied longitudinally and
transversely to the jet direction for jets with transverse momentum 20 GeV and in the pseudorapidity range . The
data sample was collected with the LHCb experiment at a center-of-mass energy
of 13 TeV, corresponding to an integrated luminosity of 1.64 fb. Triple
differential distributions as a function of the hadron longitudinal momentum
fraction, hadron transverse momentum, and jet transverse momentum are also
measured for the first time. This helps constrain transverse-momentum-dependent
fragmentation functions. Differences in the shapes and magnitudes of the
measured distributions for the different hadron species provide insights into
the hadronization process for jets predominantly initiated by light quarks.Comment: All figures and tables, along with machine-readable versions and any
supplementary material and additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-013.html (LHCb
public pages
Study of the decay
The decay is studied
in proton-proton collisions at a center-of-mass energy of TeV
using data corresponding to an integrated luminosity of 5
collected by the LHCb experiment. In the system, the
state observed at the BaBar and Belle experiments is
resolved into two narrower states, and ,
whose masses and widths are measured to be where the first uncertainties are statistical and the second
systematic. The results are consistent with a previous LHCb measurement using a
prompt sample. Evidence of a new
state is found with a local significance of , whose mass and width
are measured to be and , respectively. In addition, evidence of a new decay mode
is found with a significance of
. The relative branching fraction of with respect to the
decay is measured to be , where the first
uncertainty is statistical, the second systematic and the third originates from
the branching fractions of charm hadron decays.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-028.html (LHCb
public pages
Measurement of the ratios of branching fractions and
The ratios of branching fractions
and are measured, assuming isospin symmetry, using a
sample of proton-proton collision data corresponding to 3.0 fb of
integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The
tau lepton is identified in the decay mode
. The measured values are
and
, where the first uncertainty is
statistical and the second is systematic. The correlation between these
measurements is . Results are consistent with the current average
of these quantities and are at a combined 1.9 standard deviations from the
predictions based on lepton flavor universality in the Standard Model.Comment: All figures and tables, along with any supplementary material and
additional information, are available at
https://cern.ch/lhcbproject/Publications/p/LHCb-PAPER-2022-039.html (LHCb
public pages
Control software for equipment to measure thermal conductivity from 6 to 300 K
Abweichender Titel nach Übersetzung der Verfasserin/des VerfassersZiel dieser Diplomarbeit war es, eine Messung der thermischen Leitfähigkeit weitgehend zu automatisieren, sodass nur minimale menschliche Eingriffe nötig sind. Dazu wurde die Temperaturreglung, das Auslesen der Messgeräte und die Auswertung der Messdaten über den Kleincomputer "Rasberry Pi" via Socket-Server gesteuert. Für den Operator wurde eine grafische Benutzeroberfläche, sowie ein Server zur Fernüberwachung des Messvorgang, bereitgestellt. Das Messprinzip an sich basiert auf der Ausbildung eines stabilen Wärmestroms entlang einer Probe und anschließenden Messung dieses. Dazu wurde ein Ende der Probe mit einer konstanten Heizleistung versorgt, während das Andere auf einer konstanten Temperatur gehalten wurde. Die Temperatur wurde an drei unterschiedlichen Punkten entlang der Probe gemessen und daraus die Leitfähigkeit berechnet. Da die Leitfähigkeit besonders bei tiefen Temperaturen Aufschluss über die Transportprozesse von Material gibt, kann die Messstation durch Verdampfen von flüssigem Helium gekühlt werden. Das Messprogramm regelt dabei sowohl die Heizkurve als auch den Heliumdurchfluss. Dies erlaubt Messungen von Raumtemperatur bis 6 K. Da die thermische Leitfähigkeit besonders anfällig für äußere Einflüsse ist, wird die Messung unter Vakuum durchgeführt.The main aim of this thesis is the automatization of a thermal conductivity measurment. For this purpose the regulation of temperatur, the readout of the measurment devices and calculation of the thermal condutivity were controlled by a "Raspberry Pi" via Socket-Server. Additionally a graphical interface and a server for remote monitoring was provided. During the measurment a steady heat current along a sample was created and measured. For this purpose one end of the probe was heated with a strain gauge and the other end was kept on a constant temperatur through contact with a heat sink. The temperature along the probe was measured with thermocouples. To measure from room temperatur to 6 K the measurement the set-up could be cooled by vaporization of helium. In order to minimize the heat exchange with the environment, the measurment are conducted in a vacuum.6
Fast and radiation hard silicon detectors for the LHC-b Upgrade II
High radiation tolerance will be a key prerequisite for the vertex detectors in future hadroncollider experiments such as the LHCb Upgrade II. It is therefore of utmost importance to understand the effects radiation has on the sensor performance and how they can be mitigated. The main scope of this thesis is the study of planar hybrid silicon sensors in the fluence range of the LHCb Upgrade II using measurements combined with TCAD simulations to understand the sensor behaviour at these fluences and provide possible detector scenarios for further radiation reduction. Several test structures with a thickness of 50, 100, 200 and 300 µmrespectively were produced and characterised before irradiation by IV and CV measurement. The results were compared to simulations and used to validate the used sensor model for further simulations. A comprehensive radiation campaign with proton and neutron irradiation was done covering a fluence range from 1 × 1015 neq cm=2 to 1 × 1017 neq cm=2. After irradiation the change of leakage current and sensor signal was studied as a function of thickness and fluence. All measurements were compared to simulation using a state-of-the art radiation damage model. In addition, a fast simulation tool was developed to study possible new detector layouts and validate their performance, in particular in terms of impact parameter resolution. Using this tool, alternative detector layouts were proposed, which would reduce the radiation damage of all sensors in the detector. An extensive discussion of the impact of the RF-foil on the impact parameter resolution of the detector is also presented. ii
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The ERA-40 re-analysis
ERA-40 is a re-analysis of meteorological observations from September 1957 to August 2002 produced by the European Centre for Medium-Range Weather Forecasts (ECMWF) in collaboration with many institutions. The observing system changed considerably over this re-analysis period, with assimilable data provided by a succession of satellite-borne instruments from the 1970s onwards, supplemented by increasing numbers of observations from aircraft, ocean-buoys and other surface platforms, but with a declining number of radiosonde ascents since the late 1980s. The observations used in ERA-40 were accumulated from many sources. The first part of this paper describes the data acquisition and the principal changes in data type and coverage over the period. It also describes the data assimilation system used for ERA-40. This benefited from many of the changes introduced into operational forecasting since the mid-1990s, when the systems used for the 15-year ECMWF re-analysis (ERA-15) and the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) re-analysis were implemented. Several of the improvements are discussed. General aspects of the production of the analyses are also summarized.
A number of results indicative of the overall performance of the data assimilation system, and implicitly of the observing system, are presented and discussed. The comparison of background (short-range) forecasts and analyses with observations, the consistency of the global mass budget, the magnitude of differences between analysis and background fields and the accuracy of medium-range forecasts run from the ERA-40 analyses are illustrated. Several results demonstrate the marked improvement that was made to the observing system for the southern hemisphere in the 1970s, particularly towards the end of the decade. In contrast, the synoptic quality of the analysis for the northern hemisphere is sufficient to provide forecasts that remain skilful well into the medium range for all years. Two particular problems are also examined: excessive precipitation over tropical oceans and a too strong Brewer-Dobson circulation, both of which are pronounced in later years. Several other aspects of the quality of the re-analyses revealed by monitoring and validation studies are summarized. Expectations that the second-generation ERA-40 re-analysis would provide products that are better than those from the firstgeneration ERA-15 and NCEP/NCAR re-analyses are found to have been met in most cases. © Royal Meteorological Society, 2005. The contributions of N. A. Rayner and R. W. Saunders are Crown copyright
Considerations for the VELO detector at the LHCb Upgrade II
The LHCb experiment is planning to operate with a 7.5-fold increase in instantaneous luminosity for LHC Runs 5 and 6. The performance of the Vertex Locator detector is crucial in the event reconstruction at the increased pile-up, providing real-time information to be used in the trigger. This document presents the considerations for a future detector with timing capabilities for each track and minimal amount of material. Simulation studies indicate that a track temporal resolution of 20 ps is required to achieve the physics performance desired in Upgrade II, while keeping the same spatial resolutions as in VELO Upgrade I. Key promising technologies are listed and an R&D plan to achieve the complete set of requirements is laid out
Strategic R&D Programme on Technologies for Future Experiments - Annual Report 2020
This report summarises the activities and achievements of the strategic R&D programme on technologies for future experiments in the year 2020
Strategic R&D Programme on Technologies for Future Experiments - Annual Report 2021
This report summarises the activities and main achievements of the CERN strategic R&D programme on technologies for future experiments during the year 2021
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