Download or read book Studies of Two Particle Correlation Functions and Photon tagged Jet Fragmentation in PbPb and Pp Collisions with CMS at the LHC written by Dragos Alexandru Velicanu and published by . This book was released on 2017 with total page 113 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis studies of two particle correlations in proton-proton (pp), proton-lead (pPb), and lead-lead (PbPb) collisions, as well as jet fragmentation functions for jets paired with an isolated prompt photon in pp and PbPb collisions to better understand matter in a Quark Gluon Plasma (QGP) state. The correlation studies measure the precise hydrodynamic behavior of PbPb collisions through a Fourier analysis of charged particles emitted from the QGP and show unexpectedly strong collective behavior in high multiplicity pp and pPb collisions. The photon-tagged jet studies provide tight constraints for understanding the interactions between the jet and the Quark Gluon Plasma it traverses by both measuring the jet substructure properties via the fragmentation function, and having a sample of jets unbiased by the interactions we are trying to probe by selecting high energy photon events. These analyses are performed using data recorded by the CMS experiment at the LHC from PbPb, pPb, and pp collisions at a center of mass energy of 5.02 TeV per nucleon-nucleon pair, as well as 2.76 TeV PbPb collisions and 7 TeV pp collisions in the correlation analyses.

Download or read book Looking Inside Jets written by Simone Marzani and published by Springer. This book was released on 2019-05-11 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: This concise primer reviews the latest developments in the field of jets. Jets are collinear sprays of hadrons produced in very high-energy collisions, e.g. at the LHC or at a future hadron collider. They are essential to and ubiquitous in experimental analyses, making their study crucial. At present LHC energies and beyond, massive particles around the electroweak scale are frequently produced with transverse momenta that are much larger than their mass, i.e., boosted. The decay products of such boosted massive objects tend to occupy only a relatively small and confined area of the detector and are observed as a single jet. Jets hence arise from many different sources and it is important to be able to distinguish the rare events with boosted resonances from the large backgrounds originating from Quantum Chromodynamics (QCD). This requires familiarity with the internal properties of jets, such as their different radiation patterns, a field broadly known as jet substructure. This set of notes begins by providing a phenomenological motivation, explaining why the study of jets and their substructure is of particular importance for the current and future program of the LHC, followed by a brief but insightful introduction to QCD and to hadron-collider phenomenology. The next section introduces jets as complex objects constructed from a sequential recombination algorithm. In this context some experimental aspects are also reviewed. Since jet substructure calculations are multi-scale problems that call for all-order treatments (resummations), the bases of such calculations are discussed for simple jet quantities. With these QCD and jet physics ingredients in hand, readers can then dig into jet substructure itself. Accordingly, these notes first highlight the main concepts behind substructure techniques and introduce a list of the main jet substructure tools that have been used over the past decade. Analytic calculations are then provided for several families of tools, the goal being to identify their key characteristics. In closing, the book provides an overview of LHC searches and measurements where jet substructure techniques are used, reviews the main take-home messages, and outlines future perspectives.

Download or read book Correlations Between Jets and Charged Particles in PbPb and Pp Collisions at sNN written by CMS Collaboration and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Correlations Between Jets and Charged Particles in PbPb and Pp Collisions at sqrt s mathrm NN written by and published by . This book was released on 2016 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this study, the quark-gluon plasma is studied via medium-induced changes to correlations between jets and charged particles in PbPb collisions compared to pp reference data. This analysis uses data sets from PbPb and pp collisions with integrated luminosities of 166 inverse microbarns and 5.3 inverse picobarns, respectively, collected at $ \sqrt{s_{\mathrm{NN}}}=2.76 $ TeV. The angular distributions of charged particles are studied as a function of relative pseudorapidity ([Delta][eta]) and relative azimuthal angle ([Delta][Phi]) with respect to reconstructed jet directions. Charged particles are correlated with all jets with transverse momentum (pT) above 120 GeV, and with the leading and subleading jets (the highest and second-highest in pT, respectively) in a selection of back-to-back dijet events. Modifications in PbPb data relative to pp reference data are characterized as a function of PbPb collision centrality and charged particle pT. A centrality-dependent excess of low-pT particles is present for all jets studied, and is most pronounced in the most central events. This excess of low-pT particles follows a Gaussian-like distribution around the jet axis, and extends to large relative angles of [Delta][eta] ≈ 1 and [Delta][Phi] ≈ 1.

Download or read book Extraction of Jet Properties from Two Particle Azimuthal Correlations in Pp and AuAu Collisions at square Root of S Subscript NN written by Paul Constantin and published by . This book was released on 2004 with total page 218 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two particle azimuthal correlation functions measured in pp and AuAu collisions at [square root of s subscript NN] = 200 GeV at midrapidity with the central arms of the PHENIX detector are analyzed in order to extract the properties of hadronic jets produced in QCD vacuum and highly excited QCD media, like the jet shape parameters j[Subscript T] and k[Subscript T], the jet conditional yields (number of associated hadrons per high p[Subscript T] trigger hadron), and the jet fragmentation function. The analysis of pp data starts with the measurement of the vacuum fragmentation function from which the p[Subscript T] dependence of the mean fragmentation momentum fraction z is extracted. We obtain a constant value of z = 0.74±0.02 for p[Subscript T] above 3 GeV/c. Soft (non-perturbative) parton fragmentation becomes significant below 3 GeV/c and the slope of the fragmentation function is p[Subscript T] dependent in this region. Gaussian fits to jet induced azimuthal correlations are employed to measure the mean jet fragmentation transverse momentum j[Subscript Ty] = 359 ± 11 (stat) ± 6 (syst) MeV/c and the mean partonic transverse momentum k[Subscript Ty] = 964 ± 49 (stat) ± 16 (syst) MeV/c. The analysis of AuAu data is based on azimuthal correlation functions between charged hadrons in the 1.5-3 GeV/c and 3-5 GeV/c p[Subscript T] regions in five classes of collision centrality. The mean jet fragmentation transverse momentum j[Subscript Ty] is centrality independent and consistent with the value in pp data mentioned above. A strong broadening with the centrality of the extracted mean partonic transverse momentum k[Subscript Ty] (multiplied by z[Subscript trigg]) is observed. This is an important finding because hadronic jet quenching through energy loss is expected to be accompanied by a broadening effect. Another important finding is that the jet conditional yields in both the near (delta phi [Difference] 0) and away (delta phi [Difference] pi) regions exhibit a slightly raising trend with centrality. This was also expected to accompany the jet quenching found at higher p[Subscript T] based on simple energy conservation considerations.

Download or read book Observation and Studies of Jet Quenching in PbPb Collisions at Nucleon nucleon Center of mass Energy written by and published by . This book was released on 2011 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt: Jet production in PbPb collisions at a nucleon-nucleon center-of-mass energy of 2.76 TeV was studied with the CMS detector at the LHC, using a data sample corresponding to an integrated luminosity of 6.7 inverse microbarns. Jets are reconstructed using the energy deposited in the CMS calorimeters and studied as a function of collision centrality. With increasing collision centrality, a striking imbalance in dijet transverse momentum is observed, consistent with jet quenching. The observed effect extends from the lower cut-off used in this study (jet transverse momentum = 120 GeV/c) up to the statistical limit of the available data sample (jet transverse momentum approximately 210 GeV/c). Correlations of charged particle tracks with jets indicate that the momentum imbalance is accompanied by a softening of the fragmentation pattern of the second most energetic, away-side jet. The dijet momentum balance is recovered when integrating low transverse momentum particles distributed over a wide angular range relative to the direction of the away-side jet.

Download or read book Future Of The Large Hadron Collider The A Super accelerator With Multiple Possible Lives written by Oliver Bruning and published by World Scientific. This book was released on 2023-08-08 with total page 455 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Large Hadron Collider (LHC) is the highest energy collider ever built. It resides near Geneva in a tunnel 3.8m wide, with a circumference of 26.7km, which was excavated in 1983-1988 to initially house the electron-positron collider LEP. The LHC was approved in 1995, and it took until 2010 for reliable operation. By now, a larger set of larger integrated luminosities have been accumulated for physics analyses in the four collider experiments: ATLAS, CMS, LHCb and ALICE.The LHC operates with an extended cryogenic plant, using a multi-stage injection system comprising the PS and SPS accelerators (still in use for particle physics experiments at lower energies). The beams are guided by 1232 superconducting high field dipole magnets.Intense works are underway in preparation of the High Luminosity LHC, aimed at upgrading the LHC and detectors for collecting ten times more luminosity, and extending the collider life to the early 2040's. So far, the (HL-)LHC project represents a cumulation of around one hundred thousand person-years of innovative work by technicians, engineers, and physicists from all over the world; probably the largest scientific effort ever in the history of humanity. The book is driven by the realisation of the unique value of this accelerator complex and by the recognition of the status of high energy physics, described by a Standard Model — which still leaves too many questions unanswered to be the appropriate theory of elementary particles and their interactions.Following the Introduction are: three chapters which focus on the initial decade of operation, leading to the celebrated discovery of the Higgs Boson, on the techniques and physics of the luminosity upgrade, and finally on major options - of using the LHC in a concurrent, power economic, electron-hadron scattering mode, when upgraded to higher energies or eventually as an injector for the next big machine. The various technical and physics chapters, provided by 61 authors, characterise the fascinating opportunities the LHC offers for the next two decades ahead (possibly longer), with the goal to substantially advance our understanding of nature.

Download or read book Study of Double Parton Scattering in Photon 3 Jets Final State written by You-Hao Chang and published by Springer. This book was released on 2017-01-20 with total page 107 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book mainly focuses on the study of photon + 3 jets final state in Proton-Proton Collisions at √s = 7TeV, searching for patterns of two (or more) distinct hard scatterings in the same collision, i.e the so-called Double Parton Scattering (DPS). A new method by using Monte Carlo generators was performed and provides higher order corrections to the description of the Single Parton Scattering (SPS) background. Further it is investigated whether additional contributions from DPS can improve the agreement between the measured data and the Monte Carlo predictions. The current theoretical uncertainties related to the SPS background are found to be larger than expectation. At the same time a rich set of DPS-sensitive measurements is reported for possible further interpretation.

Download or read book Properties of Dijets in Pp PPb and PbPb Collisions written by Doga Can Gulhan and published by . This book was released on 2016 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt: Two dijet measurements, one using 35 pb-1 pPb data at [square root]sNN- 5.02 TeV, and another with 166 [mu]b-1 PbPb and 5.3 pb-1 pp data at [square root]sNN = 2.76 TeV collected with CMS detector at the LHC, are presented. In pPb collisions, the dijet PT ratios, azimuthal angle differences and pseudorapidity distributions are measured and compared to PYTHIA and PYTHIA+HIJING simulations as well as NLO QCD predictions for the latter observable. No significant signs of final state interactions, such as a decrease in the mean dijet PT ratios or a broadening in the correlation of the dijets in azimuthal angle, with increasing forward activity, are observed. The dijet pseudorapidity distributions are also measured, and are sensitive to nuclear PDFs for x values of 0.001 - 0.5. Selections on event activity are found to yield unexpected centrality biases on dijet pseudorapidity distributions, which aided the interpretation of similar biases seen in inclusive jet measurements by ATLAS. In PbPb collisions, a detailed scan of charged particle distributions in correlation with the dijet system is carried out. The PT projection of charged particles on the dijet axis is measured at different distances of [delta] = [mathematical formula ...] 2 with respect to the leading and subleading jet axes. In this way, the spectra and angular distribution of the additional particles, which recover the overall event balance in dijet events with enhanced PT asymmetry in PbPb compared to pp collisions, are obtained up to [delta] = 1.8 in steps of 0.2. A significant excess of low PT particles associated with a subleading jet at large [delta] values is observed, and this excess is shown to get larger for dijet events with PT asymmetry. The scan is carried out for variety of anti-kT R parameters, which provides a way of varying jet width and fragmentation. Medium response to jet quenching at wide angles for jets with different fragmentation is studied. Only an insignificant increase of the magnitude of low PT particle excess at large angles, but a significant increase in the modification of the balance distribution close to the jet axes is observed by increasing R.

Download or read book Principal component Analysis of Two particle Azimuthal Correlations in PbPb and PPb Collisions at CMS written by CMS Collaboration and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Measurement of Inclusive Jet Charged particle Fragmentation Functions in Pb Pb Collisions at sqrt s mathrm NN written by and published by . This book was released on 2015 with total page 23 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Two particle Momentum Correlation in Jets at the Tevatron written by Sergo Jindariani and published by . This book was released on 2006 with total page 3 pages. Available in PDF, EPUB and Kindle. Book excerpt: Presented are the measurements of two-particle momentum correlations in jets produced in p-pbar collisions at center of mass frame energy 1.96 TeV. Studies were performed for charged particles within a restricted opening angle of 0.5 rad around the jet axis and for dijet events with various dijet masses. Comparison of the experimental results to the theoretical predictions obtained for partons within the framework of the resummed perturbative QCD (Next-to-Leading Log Approximation) shows that the parton momentum correlations do survive the hadronization stage of jet fragmentation, thus, giving further support to the hypothesis of Local Parton-Hadron Duality.

Download or read book Evidence for Collective Multiparticle Correlations in P Pb Collisions written by and published by . This book was released on 2015 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: The second-order azimuthal anisotropy Fourier harmonics, v2, are obtained in p-Pb and PbPb collisions over a wide pseudorapidity ([eta]) range based on correlations among six or more charged particles. The p-Pb data, corresponding to an integrated luminosity of 35 nb-1, were collected during the 2013 LHC p-Pb run at a nucleon-nucleon center-of-mass energy of 5.02 TeV by the CMS experiment. A sample of semiperipheral PbPb collision data at √sNN=2.76 TeV, corresponding to an integrated luminosity of 2.5 [mu]b-1 and covering a similar range of particle multiplicities as the p-Pb data, is also analyzed for comparison. The six- and eight-particle cumulant and the Lee-Yang zeros methods are used to extract the v2 coefficients, extending previous studies of two- and four-particle correlations. For both the p-Pb and PbPb systems, the v2 values obtained with correlations among more than four particles are consistent with previously published four-particle results. These data support the interpretation of a collective origin for the previously observed long-range (large [Delta][eta]) correlations in both systems. The ratios of v2 values corresponding to correlations including different numbers of particles are compared to theoretical predictions that assume a hydrodynamic behavior of a p-Pb system dominated by fluctuations in the positions of participant nucleons. These results provide new insights into the multiparticle dynamics of collision systems with a very small overlapping region.

Download or read book Study of Jet Quenching with Z jet Correlations in PbPb and Pp Collisions at sqrt s NN written by and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The production of jets in association with Z bosons, reconstructed via the mu+mu- and e+e- decay channels, is studied in pp and, for the first time, in PbPb collisions. Both data samples were collected by the CMS experiment at the LHC, at a center-of-mass energy of 5.02 TeV. The PbPb collisions were analyzed in the 0-30% centrality range. The back-to-back azimuthal alignment was studied in both pp and PbPb collisions for Z bosons with transverse momentum ptz> 60 GeV/c and a recoiling jet with ptj> 30 GeV/c. The pt imbalance, xjz= ptj/ptz, as well as the average number of jet partners per Z, rjz, were studied in intervals of ptz, in both pp and PbPb collisions. The rjz is found to be smaller in PbPb than in pp collisions, which suggests that in PbPb collisions a larger fraction of partons, associated with the Z bosons, lose energy and fall below the 30 GeV/c ptj threshold.

Download or read book Basics of Perturbative QCD written by Yuri Dokshitzer and published by Atlantica Séguier Frontières. This book was released on 1991 with total page 286 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Properties of Fragmentation Photons in P p Collisions at 200 GeV Center of Mass Energy written by Janette Alice Hanks and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The use of two-particle correlations coupled with a sophisticated method for identifying and removing decay photons has made it possible to further study the jet properties of these fragmentation photons, in the form of pout and root mean square jT. These results will help to constrain both the underlying theoretical description of direct photon production in p + p, and modifications expected in heavy ion collisions.

Download or read book Observation of Charge dependent Azimuthal Correlations in PPb Collisions and Its Implication for the Search for the Chiral Magnetic Effect written by and published by . This book was released on 2016 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Charge-dependent azimuthal particle correlations with respect to the second-order event plane in pPb and PbPb collisions at a nucleon-nucleon center-of-mass energy of 5.02 TeV have been studied with the CMS experiment at the LHC. The measurement is performed with a three-particle correlation technique, using two particles with the same or opposite charge within the pseudorapidity range abs(eta)