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Author: Publisher: ISBN: Category : Languages : en Pages : 188
Book Description
The dominant background in searches for a Higgs boson decaying into b-quarks at the Tevatron is production of a Z boson in association with either b- or c-quark initiated jets (b or c jets). This thesis describes the first measurements of the ratio of differential cross sections [sigma] (Z + b jet)/ [sigma](Z + jet), and the first measurements of the ratio of cross sections [sigma] (Z + c jet)/ [sigma](Z + jet) and [sigma] (Z + c jet)/ [sigma](Z + b jet). These measurements are performed using the full D0 Run II data set corresponding to an integrated luminosity of 9.7 fb-1. The ratio of differential cross sections [sigma](Z + b jet)/[sigma] (Z + jet) have been measured as a function of jet and Z boson pT, jet [eta], and [Delta][phi](Z, jet). The Z+c jet ratios of differential cross sections are measured as a function of jet and Z boson pT.
Author: Publisher: ISBN: Category : Languages : en Pages : 188
Book Description
The dominant background in searches for a Higgs boson decaying into b-quarks at the Tevatron is production of a Z boson in association with either b- or c-quark initiated jets (b or c jets). This thesis describes the first measurements of the ratio of differential cross sections [sigma] (Z + b jet)/ [sigma](Z + jet), and the first measurements of the ratio of cross sections [sigma] (Z + c jet)/ [sigma](Z + jet) and [sigma] (Z + c jet)/ [sigma](Z + b jet). These measurements are performed using the full D0 Run II data set corresponding to an integrated luminosity of 9.7 fb-1. The ratio of differential cross sections [sigma](Z + b jet)/[sigma] (Z + jet) have been measured as a function of jet and Z boson pT, jet [eta], and [Delta][phi](Z, jet). The Z+c jet ratios of differential cross sections are measured as a function of jet and Z boson pT.
Author: Joseph Anthony Zennamo Publisher: ISBN: Category : Languages : en Pages : 161
Book Description
The dominant background in searches for a Higgs boson decaying into $b$-quarks at the Tevatron is production of a $Z$ boson in association with either $b$- or $c$-quark initiated jets ($b$ or $c$ jets). This thesis describes the first measurements of the ratio of differential cross sections $\sigma(Z+b\mbox{ jet})/\sigma(Z+\mbox{jet})$, and the first measurements of the ratio of cross sections $\sigma(Z+c\mbox{ jet})/\sigma(Z+\mbox{jet})$ and $\sigma(Z+c\mbox{jet})/\sigma(Z+b\mbox{ jet})$. These measurements are performed using the full D0 Run II data set corresponding to an integrated luminosity of 9. 7 fb$^{-1}$. The ratio of differential cross sections $\sigma(Z+b\mbox{ jet})/\sigma(Z+\mbox{jet})$ have been measured as a function of jet and $Z$ boson $p_{T}$, jet $\eta$, and $\Delta\varphi(Z,\mbox{jet})$. The $Z+c\mbox{ jet}$ ratios of differential cross sections are measured as a function of jet and $Z$ boson $p_{T}$.
Author: Publisher: ISBN: Category : Languages : en Pages : 11
Book Description
We present a next-to-leading-order calculation of the production of a Z boson with two jets, one or more of which contains a heavy quark (Q = c, b). We show that the cross section with only one heavy-quark jet is larger than that with two heavy-quark jets at both the Fermilab Tevatron and the CERN LHC. These processes are the dominant irreducible backgrounds to a Higgs boson produced in association with a Z boson, followed by h --> b{bar b}. Our calculation makes use of a heavy-quark distribution function, which resums collinear logarithms and makes the next-to-leading-order calculation tractable.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
We present the first complete calculation of Z-boson production in association with a jet in hadronic collisions through next-to-next-to-leading order in perturbative QCD. Our computation uses the recently proposed N-jettiness subtraction scheme to regulate the infrared divergences that appear in the real-emission contributions. We present phenomenological results for 13 TeV proton-proton collisions with fully realistic fiducial cuts on the final-state particles. The remaining theoretical uncertainties after the inclusion of our calculations are at the percent level, making the Z+jet channel ready for precision studies at the LHC run II.
Author: Publisher: ISBN: Category : Languages : en Pages :
Book Description
Measurements of the associated production of a Z boson with at least one jet originating from a b quark in proton-proton collisions at $\sqrt{s}$ = 8 TeV are presented. Differential cross sections are measured with data collected by the CMS experiment corresponding to an integrated luminosity of 19.8 inverse femtobarns. Z bosons are reconstructed through their decays to electrons and muons. Cross sections are measured as a function of observables characterizing the kinematics of the b jet and the Z boson. Ratios of differential cross sections for the associated production with at least one b jet to the associated production with any jet are also presented. The production of a Z boson with two b jets is investigated, and differential cross sections are measured for the dijet system. Results are compared to theoretical predictions, testing two different flavour schemes for the choice of initial-state partons.
Author: Publisher: ISBN: Category : Languages : en Pages : 189
Book Description
The production of jets in association with a Z/?* boson is an example of an important class of processes at hadron colliders, namely vector boson + jet (V + jet) production. Comparisons of measurements of this class of processes with theory predictions constitute an important, fundamental test of the Standard Model of particle physics, and of the theory of QCD in particular. While having a smaller cross section than other V +jet processes, Z/?*(→ e+e-) + jets production, with Z/?* → e+e-/?+?-, has a distinct experimental signature allowing for measurements characterized by low backgrounds and a direct, precise measurement of the properties of the decay products of the Z/?* boson. In this thesis, several new measurements of the properties of jets produced in association with a Z/?* boson in p$ar{p}$ collisions at √s = 1.96 TeV are presented. The cross section for Z/?*(→ e+e-) + N jet production (N ≤ 3) is measured, differential in the transverse momentum of the Nth jet in the event, normalized to the inclusive Z/?* cross section. Also, the cross section for Z/?*(→e+e-) + N jets (N ≥ 1) is measured, differential in the difference in azimuthal angle between the di-electron system and any jet in the event, normalized to unity. The data used in the measurements were collected by the D0 experiment located at the Tevatron Collider of the Fermi National Accelerator Laboratory and correspond to an integrated luminosity of 1.04 fb-1. The measured jet transverse momentum spectra are compared with the predictions of perturbative calculations at the next-to-leading order in the strong coupling constant. Given the low sensitivity of the calculations to model parameters, these comparisons represent a stringent test of perturbative QCD. One of the main goals currently being pursued in particle physics is the discovery of the only particle predicted by the Standard Model which has so far no been detected experimentally, namely the Higgs boson. It is assumed that the ATLAS and CMS experiments located at the Large Hadron Collider (LHC), a proton-proton collider at √s = 14 TeV, will be able to detect the Higgs boson, or rule out its existence, within the next few years. The collisions delivered by the LHC will also be used to perform a long range of searches for other new particles, for instance particles predicted by models based on the principle of supersymmetry. The associated production of vector bosons with jets has relatively large production rates at the LHC and can produce a long list of different final states which can include charged leptons, missing transverse energy, as well as light- and heavy-flavour jets. This makes V + jet production a major source of background events to many searches for new particles. Most techniques used for estimating the expected number of background events to searches rely on passing the stable final-state particles of simulated hadron collisions generated using a so-called event generator code, through a simulation of the experimental detector system. The development of event generators which are capable of reliably predicting the properties of jets produced in association with a core process, e.g. the production of a vector boson, has been the subject of a large amount of research activity during the last ten years. These efforts have led to the appearance of the CKKW and MLM algorithms which are implemented in several event generators, among them SHERPA and ALPGEN + PYTHIA. The large data sample collected by the D0 experiment during Run II offers an excellent opportunity for validating these new event generators against experimental measurements of V + jet production. As argued above, the Z/?*(→ e+e-) + jets process offers the combination of a clean experimental signature and large production rates, making it the process of choice for these studies.
Author: Simone Marzani Publisher: Springer ISBN: 3030157091 Category : Science Languages : en Pages : 205
Book Description
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.
Author: Publisher: ISBN: Category : Languages : en Pages : 4
Book Description
The CDF Collaboration has a comprehensive program of studying the production of vector bosons, W and Z, in association with energetic jets. Excellent understanding of the standard model W/Z+jets and W/Z+c, b-jets processes is of paramount importance for the top quark physics and for the Higgs boson and many new physics searches. We review the latest CDF results on Z-boson production in association with inclusive and b-quark jets, study of the p{sub T} balance in Z+jet events, and a measurement of the W+charm production cross section. The results are based on 4-5 fb−1 of data and compared to various Monte Carlo and next-to-leading order perturbative QCD predictions.
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