Jet Measurements Research Articles

A Brief Review of CMS Jet Measurements

We present an overview of the current status of the recent jet measurements in PbPb and pp collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV that are studied with the CMS detector at the LHC. Jets are reconstructed using the anti-kT sequential reconstruction algorithm on particle flow objects. To distinguish between different possible energy loss mechanisms and to provide an important experimental check on the validity of the assumed jet fragmentation, inclusive jets, flavor tagged jets and jet shapes are studied.

Effect of ambient pressure on local concentration measurement of transient hydrogen jet in a constant-volume vessel using spark-induced breakdown spectroscopy

We report an investigation of the effects of the ambient pressure on fuel concentration measurements of an injected jet of hydrogen using spark-induced breakdown spectroscopy (SIBS) in a constant-volume vessel. Measurements were carried out using hydrogen injected into a nitrogen environment with different ambient pressures, and the local concentrations were measured at various spark locations. The optical emission from the spark discharge at 501 nm (corresponding to nitrogen) and 656 nm (corresponding to hydrogen) was observed using SIBS. Spectrally resolved emission from the plasma was detected simultaneously using a spectrometer. The potential to determine the hydrogen/nitrogen ratio in the spark gap using was demonstrated. Spectral calibration was carried out using a hydrogen/nitrogen mixture, and hydrogen was injected at a pressure of 5.0 MPa into nitrogen with ambient pressures in the range 0.5–1.5 MPa. The results show an increase in the background radiation, as well as of the peaks corresponding to hydrogen and nitrogen atomic emission lines, as the ambient pressure increased. An increase in the density of nitrogen inside the chamber influenced the structure of the hydrogen jet, slowing the spray and reducing penetration, which altered the equivalence ratio at the location of the spark. When the spark occurred during injection, the behavior of the hydrogen jet was quasi-steady state; when the spark timing followed the injection, however, an unsteady state was observed.

Design Studies of the Calorimeter Systems for the sPHENIX Experiment at RHIC and Future Upgrade Plans

The PHENIX Experiment at RHIC is planning a series of major upgrades that will enable a comprehensive measurement of jets in relativistic heavy ion collisions, provide enhanced physics capabilities for studying nucleon-nucleus and polarized proton collisions, and allow a detailed study of electron-nucleus collisions at the Electron Ion Collider at Brookhaven (eRHIC). The first of these upgrades, sPHENIX, will be based on the former BaBar magnet and will include a hadronic calorimeter and new electromagnetic calorimeter that will cover ±1.1 units in pseudorapidity and 2π in azimuth in the central region, resulting in a factor of 6 increase in acceptance over the present PHENIX detector. The electromagnetic calorimeter will be a tungsten scintillating fiber design with a radiation length ~ 7 mm and a Moliere radius ~ 2 cm. It will have a total depth of ~ 18 radiation lengths and an energy resolution ~ 15%/√E. The hadronic calorimeter will consist of steel plates with scintillating tiles in between that are read out with wavelength shifting fibers, It will have a total depth of ~ 5 interaction lengths and an energy resolution 100%/√E. Both calorimeters will use silicon photomultipliers as the readout sensor. Detailed design studies and Monte Carlo simulations for both calorimeters have been carried out and prototype detectors have been constructed and tested in a test beam at Fermilab in February 2014. This contribution describes these design studies for the sPHENIX experiment and its future upgrade plans at RHIC.

Measurement of multijet production in $${e\!\!\;p}$$ e p collisions at high $$\varvec{Q^2}$$ Q 2 and determination of the strong coupling $$\varvec{{\alpha _s}} $$ α s

Inclusive jet, dijet and trijet differential cross sections are measured in neutral current deep-inelastic scattering for exchanged boson virtualities \(150 < Q^2 < 15\,000\,{\mathrm {GeV}^2}\) using the H1 detector at HERA. The data were taken in the years 2003 to 2007 and correspond to an integrated luminosity of \(351~\mathrm {pb}^{-1}\). Double differential Jet cross sections are obtained using a regularised unfolding procedure. They are presented as a function of \(Q^2\) and the transverse momentum of the jet, \(P_\mathrm{T}^\mathrm{jet}\), and as a function of \(Q^2\) and the proton’s longitudinal momentum fraction, \(\xi \), carried by the parton participating in the hard interaction. In addition normalised double differential jet cross sections are measured as the ratio of the jet cross sections to the inclusive neutral current cross sections in the respective \(Q^2\) bins of the jet measurements. Compared to earlier work, the measurements benefit from an improved reconstruction and calibration of the hadronic final state. The cross sections are compared to perturbative QCD calculations in next-to-leading order and are used to determine the running coupling and the value of the strong coupling constant as \(\alpha _s(M_Z) = 0.1165 \;\, (8)_\mathrm{exp} \;\, (38)_\mathrm{pdf,theo}\).

PIV measurements in a turbulent wall jet over a backward-facing step in a three-dimensional, non-confined channel

A study of a turbulent wall jet over a backward-facing step is especially of interest because it shows a rich phenomenon flow and a mechanism to alter the flow characteristics downstream of the step. However, studies on this flow configuration are rare. In this paper, we considered this flow configuration in a non-confined channel as the specific engineering applications of electrical rotating machines and alternator that can be found in modern wind generators of the power production industry and automobile engines. The turbulent wall jet over a backward-facing step in a non-confined wind tunnel had the jet Reynolds number of 24,100 and the step Reynolds number of 11,900. Particle image velocity (PIV) and stereoscopic PIV measurements were performed along the central plane and several cross-stream planes. Numerical simulation of the test configuration was conducted by solving the three-dimensional Reynolds Averaged Navier–Stokes (RANS) equations with the second-order closure Reynolds stress model (RSM). The mean flow fields and second-order statistical moments from the RSM simulation were compared to results that were obtained through the PIV and stereo-PIV experiments. The mean reattachment length obtained from the current configuration was much shorter than those from the backward-facing step in the plane channel. The stereo-PIV measurements in the cross-stream planes revealed a high three-dimensionality of the flow, a high population of streamwise vortice in the upper region, near the side walls and the corners formed by the side walls and the bottom wall. The obtained results also confirmed the presence of the wall-jet formation on the bottom wall.

A turbulence model for large interfaces in high Reynolds two-phase CFD

A model for two-phase (six-equation) CFD modelling of turbulence is presented, for the regions of the flow where the liquid–gas interface takes place on length scales which are much larger than the typical computational cell size. In the other regions of the flow, the liquid or gas volume fractions range from 0 to 1. Heat and mass transfer, compressibility of the fluids, are included in the system, which is used at high Reynolds numbers in large scale industrial calculations. In this context, a model based on k and ɛ transport equations in each phase was chosen. The paper describes the model, with a focus on the large interfaces, which require special treatments and transfer terms between the phases, including some approaches inspired from wall functions. The validation of the model is based on high Reynolds number experiments with turbulent quantities measurements of a liquid jet impinging a free surface and an air water stratified flow. A steam–water stratified condensing flow experiment is also used for an indirect validation in the case of heat and mass transfer.

Towards a Consistent Description of In-medium Parton Branching

Ultra-relativistic heavy-ion collisions are a window of opportunity to study QCD matter under extreme conditions of temperature and density, such as the quark-gluon plasma. Among the several possibilities, the study of jet quenching - generic name given to in-medium energy loss modifications of the parton branching - is a powerful tool to assess the properties of this new state of matter. The description of the parton shower is very well understood in vacuum (controlled reference) and medium-induced modifications of this process can be experimentally accessed through jet measurements. Current experimental data, however, cannot be entirely described only with energy loss phenomena. Transverse momentum broadening and decoherence effects, both theoretically established by now, and their interplay are essential to build a consistent picture of the medium-modifications of the parton branching and to achieve a correct description of the current experimental data. In this write-up, we will present the latest developments that address such unified description.

Measurements of vector boson plus jets from ATLAS

Measurements of single W, Z boson production in association with jets probe QCD in multi-scale environment. Measurements of W + jet and Z + jet production and their ratio, extending to high jet multiplicities, and a large set of kinematic distributions are presented for 7 TeV data. The results are compared to the predictions of modern Monte Carlo generators. The production of vector bosons plus heavy flavors is sensitive to the c and b quark parton distribution functions (PDFs) and gluon splitting effects. Measurements of W + c and Z + b (b ) are reported and compared to predictions based on various PDFs in 4 and 5 flavour schemes. An overview of the results is given.

Measurements of vector boson plus jets from ATLAS

Measurements of single W, Z boson production in association with jets probe QCD in multi-scale environment. Measurements of W + jet and Z + jet production and their ratio, extending to high jet multiplicities, and a large set of kinematic distributions are presented for 7 TeV data. The results are compared to the predictions of modern Monte Carlo generators. The production of vector bosons plus heavy flavors is sensitive to the c and b quark parton distribution functions (PDFs) and gluon splitting effects. Measurements of W + c and Z + b(b) are reported and compared to predictions based on various PDFs in 4 and 5 flavour schemes. An overview of the results is given.

Numerical Modelling of Turbulent Particle-laden Sonic CO2 Jets with Experimental Validation

Under-expanded particle-laden flows resulting in velocities greater than the local speed of sound are a feature of a wide number of applications in aviatic, astronautical, and process engineering scenarios including those relating to the accidental release of high-pressure fluids from reservoirs or pipelines. Such pipelines are considered to be the most likely method for transportation of captured carbon dioxide (CO2) from power plants and other industries prior to subsequent storage in carbon capture and storage (CCS) applications. Their safe operation is of paramount importance as their contents are likely to be in the region of several thousand tonnes. CO2 poses a number of dangers upon release due to its physical properties. It is a colourless and odourless asphyxiant which has a tendency to sublimation and solid formation, and is directly toxic if inhaled in air at concentrations around 5%, and likely to be fatal at concentrations around 10%. The developments presented in this paper concern the formulation of a multi-phase homogeneous discharge and dispersion model capable of predicting the near-field fluid dynamic, phase and particle behaviour of such CO2 releases, with validation against measurements of laboratory-scale jet releases of CO2 recently obtained by our group.

S0510202 低レイノルズ数円形噴流乱流の低解像度二次元PIV測定

In this study, we carried out a low resolution 2D-PIV(Particle Image Velocimetry) measurement of low Reynolds number turbulent round jet. The spatial resolution was of the order of Taylor micro-scale and under-estimates the turbulence energy. Mean velocity statistics coincided with the standard reference. Second and third order statistics qualitatively in good agreement with the previous studies. The difference between the results is due to a loss of turbulence energy and the Reynolds number dependence. Nevertheless, the results showed the self-preserving property in far field region.

Jet production and measurements ofαsat HERA

Jet production and measurements of<i>α_s</i>at HERA

Future Upgrades for the PHENIX Experiment at RHIC: From PHENIX to sPHENIX and Beyond

A series of major upgrades are being planned for the PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) to enable a comprehensive measurement of jets and quarkonia in relativistic heavy ion collisions in order to study the phase transition of normal nuclear matter to the Quark Gluon Plasma near its critical temperature. These upgrades will include a number of major new detector systems. The former BaBar solenoid magnet will be incorporated in the first stage, sPHENIX. Further upgrades will include two new large calorimeters. In the following these upgrades and their requirements are being presented.

Standard Model measurements with the ATLAS detector

Various Standard Model measurements have been performed in proton-proton collisions at a centre-of-mass energy of √ s = 7 and 8 TeV using the ATLAS detector at the Large Hadron Collider. A review of a selection of the latest results of electroweak measurements, W/Z production in association with jets, jet physics and soft QCD is given. Measurements are in general found to be well described by the Standard Model predic- tions. been performed in proton-proton collisions at a centre-of-mass energy of √ s = 7 and 8 TeV using the ATLAS detector (1) at the LHC. These allow for precision tests of the electroweak dynamics of the Standard Model, but also challenge next-to-next-to-leading-order predictions. Differences between measurements and Standard Model predictions could prove evidence for new phenomena. Recent Quantum Chromo Dynamics (QCD) results highlight the importance of precision QCD measurements for improving state-of-the-art theoretical tools and searching for new physics. A selection of the latest results of electroweak measurements, W/Z production in association with jets, jet physics and soft QCD is reported. These consist of the measurement of the WW cross section, first evidence of the electroweak production of W ± W ± jj , and electroweak Zj jproduction. Measurements are in general found to be well described by the Standard Model predictions. Measurements of differential produc- tion cross sections of a Z boson in association with b-jets, the production cross section of the W boson in association with jets as well as the ratio of the production cross sections for W and Z bosons in association with jets are presented. The measurements are compared to next-to-leading-order pertur- bative QCD calculations and to predictions from different Monte Carlo (MC) generators implement- ing leading-order matrix elements supplemented by parton showers. Various inclusive, differential or double differential jet measurements are presented. The dominant experimental uncertainty on these measurements comes from the jet energy scale. Next-to-leading order QCD calculations corrected to account for non-perturbative effects are compared to the measurements. A good agreement between the data and the theoretical predictions based on most of the global parton distribution functions is found over the full kinematic range, covering almost seven orders of magnitude in the measured cross-section values. A measurement of charged-particle distributions sensitive to the properties of

Jet Production at HERA and Determination of [formula omitted

Inclusive jet, dijet and trijet differential cross sections are measured [H1 Collab., DESY-14-089, [arXiv:1406.4709]] in neutral current deep-inelastic scattering (DIS) for exchanged boson virtualities 150<Q2<15000 GeV2 using the H1 detector at HERA. The data were taken in the years 2003 to 2007 and correspond to an integrated luminosity of 351pb−1. Jet cross sections are obtained using a regularised unfolding procedure. Normalised differential jet cross sections are also measured as the ratio of the jet cross sections to the inclusive neutral current cross sections in the respective Q2 bins of the jet measurements. The cross sections are used to determine the strong coupling constant αs=0.1165 (8)exp (38)pdf,theo.Trijet differential cross sections are measured [ZEUS Collab., ZEUS-prel-14-008] in neutral current DIS for 125<Q2<20000 GeV2 using the ZEUS detector at HERA. Good agreement between data and NLO calculations is observed.

Flow Visualization and Measurement of a Synthetic Jet Actuator Performance Using PIV System

This paper presents the performance of a piezoelectric Synthetic Jet Actuator (SJA) in quiescent flow. Pulse jet velocity and vorticity were taken as the parameter to evaluate the performance of SJA. PIV measurements on the jet flow at the orifice exit of a round SJA were conducted by varying the oscillating in frequency and voltage. The location of 5mm above orifice was identified as the optimum location for maximum pulse jet measurements. The maximum pulse jet velocity and vorticity obtained were 18.77 m/s and 242.5s-1. The PIV experiment showed that by varying oscillating frequency at fixed input voltage, the performance of SJA was greatly affected by Helmholtz resonance. While in the investigation of varying input voltage at fixed oscillating frequency, diaphragm defection was the parameter that affects the performance of the SJA. Besides, PIV measurement showed that the flow patterns of vortex structure formation were affected by the oscillating frequency and pulse jet velocity.

PIV study of large-scale flow organisation in slot jets

The paper reports on particle image velocimetry (PIV) measurements in turbulent slot jets bounded by two solid walls with the separation distance smaller than the jet width (5–40%). In the far-field such jets are known to manifest features of quasi-two dimensional, two component turbulence. Stereoscopic and tomographic PIV systems were used to analyse local flows. Proper orthogonal decomposition (POD) was applied to extract coherent modes of the velocity fluctuations. The measurements were performed both in the initial region close to the nozzle exit and in the far fields of the developed turbulent slot jets for Re⩾10,000. A POD analysis in the initial region indicates a correlation between quasi-2D vortices rolled-up in the shear layer and local flows in cross-stream planes. While the near-field turbulence shows full 3D features, the wall-normal velocity fluctuations day out gradually due to strong wall-damping resulting in an almost two-component turbulence. On the other hand, the longitudinal vortex rolls take over to act as the main agents in wall-normal and spanwise mixing and momentum transfer. The quantitative analysis indicates that the jet meandering amplitude was aperiodically modulated when arrangement of the large-scale quasi-2D vortices changed between asymmetric and symmetric pattern relatively to the jet axis. The paper shows that the dynamics of turbulent slot jets are more complex than those of 2D, plane and rectangular 3D jets. In particular, the detected secondary longitudinal vortex filaments and meandering modulation is expected to be important for turbulent transport and mixing in slot jets. This issue requires further investigations.

Jet production and structure in pp, p–Pb and Pb–Pb collisions measured by ALICE

In ultra-relativistic heavy-ion collisions a hot, dense medium of strongly interacting matter called the Quark Gluon Plasma (QGP) is formed. One of the main goals of jet measurements is to study how the fragmentation of hard scattered partons is modified as they traverse the medium. A study of jet spectra and correlations in a variety of colliding systems will allow a better understanding of the detailed mechanisms of the in-medium energy loss and will further constrain theoretical models for this process. This work will report the recent ALICE results on jet production, di-jet acoplanarity kT and hadron+jet correlations in pp, p–Pb and Pb–Pb collisions and discuss their sensitivity to a modified jet fragmentation function.

Turbulence measurements of a personal airflow outlet jet in aircraft cabin

The jet airflow field of MD-82 aircraft cabin's personal airflow outlet (PAO) is measured by constant-temperature anemometry system with the resolution higher than the smallest time-scale of turbulence. The turbulence statistics at different radial and axial positions is analyzed. The airflow field of the PAO jet is similar to a single jet beyond the point of reattachment. However, the airflow diffuses stronger than the single jet, turbulence intensity is higher, each order turbulence statistics and characteristics scales get turbulent equilibrium earlier. The inertial sub-range is found by spectrum analysis, by which the energy is cascaded from the energy-containing large scale to the small scale, and finally dissipated into heat. Moreover, wavelet analysis is employed to perform multi-scale decomposition of instantaneous turbulence fluctuating velocity signals, in order to accurately distinguish the time scales which dominate the airflow field.

Jet suppression in Pb+Pb collisions with the ATLAS detector

Abstract The phenomenon of the jet quenching in the hot and dense medium created in ultra-relativistic heavy-ion collisions was established at RHIC experiments. The measurement of jets provides a powerful tool to probe the hot and dense medium and the interaction of the scattered parton while crossing the hot and dense medium. Results are presented from ATLAS measurements of inclusive jet production, azimuthal dependence of jet yields and jet fragmentation. Measurements are performed using the Pb+Pb collision data collected during the 2010 and 2011 LHC runs at the nucleon–nucleon center of mass energy of 2.76 TeV.