Includes bibliographical references. / A review and application of the Hadron Gas model to data gathered from heavy ion collision experiments in search of the Quark Gluon Plasma. The Hadron Gas model is extended by ensuring overall charge conservation of the collision system at freeze-out. Conclusions of thermal and chemical equilibrium at freeze-out are drawn from an analysis of the data of Si-Au collisions at BNL-AGS, and compared with the literature on thermal analyses of Si-Au collisions.

In this dissertation we investigate the question that high energy irregular rapidity events can be generated by finite samples of one dimensional fractal structures. The idea is basically to generate a rapidity histogram by transforming a one-dimensional map of which the histogram is known and simple a one-dimensional map with the desired histogram. Then studying the system in different dynamical regimes we analyse the properties of factorial moments, cumulants and multifractal properties. It is useful to have such models in the sense that one then has a direct ability to check some of the quantitative features that can be distinguished from each other because they refer to different dynamical regimes (i.e. intermittency and chaos). In studying such models we analyse the qualitative and quantitative features of the question of hadronic intermittency in comparison with the same features in those models both theoretically and experimentally. We finally made an analogy with the field theory formalism of hadron production and Quantum Optics in which the question of regularity vs. irregularity has been asked much earlier.

Searches are made for narrow diboson resonances, ZZ and ZW, in the final states llqq and ννqq at ATLAS, with (13.2±0.4) fb−1data collected from pp-collisions with center of mass energy √ s=13 TeV during 2015 and 2016, the first two years of Run 2 of the Large Hadron Collider. The hadronic decay products of the vector boson, V → qq, are reconstructed as jets in the electromagnetic and hadronic calorimeters. When the vector boson is sufficiently boosted the decay products are reconstructed as a single anti-kt R = 1.0 jet. Otherwise two anti-kt R = 0.4 jets are matched to identify the vector boson. The Z boson in its leptonic decay is identified by either reconstructing two electrons in the calorimeters, or opposite sign muons in the muon spectrometer. Limits on the production cross section for 3 benchmark signals, a heavy scalar, a spin-1 heavy vector triplet, and a spin-2 graviton are set in the mass range 300 GeV to 5000 GeV.

A search is presented for new resonances decaying to a pair of boosted Standard Model bosons, WV, where the W boson decays leptonically (W → lν, with l = e, µ) and the other weak boson, V (V=W,Z), decays hadronically (V → qq¯ 0/qq¯, with q, q0 = u, d, c, s, b). The data were collected with the ATLAS detector at the CERN Large Hadron Collider, during the 2015 and 2016 periods of pp collisions, at a center-of-mass energy √s = 13 TeV, and correspond to a total integrated luminosity of 36.1 fb^−1. The hadronic decay of the boosted $V$ boson is reconstructed as a single large-radius jet, and the leptonic decay of the W boson is reconstructed as a lepton and missing transverse energy. The search is sensitive to resonances produced with quark-antiquark fusion, gluon-gluon fusion, and vector-boson fusion. No significant excesses are observed above the Standard Model background prediction. Upper limits on production cross section times branching ratio to WV are set at a 95 % confidence level for selected benchmark signal models. Models of a neutral, narrow scalar boson (spin-0), charged and neutral vector bosons (spin-1) coupling to the Standard Model gauge bosons, and a neutral Randall-Sundrum bulk graviton (spin-2) are considered. The search significantly improves the limits produced in recent searches.

The PANDA experiment is one of the main pillars of the Facility for Antiproton and Ion Research (FAIR), currently under construction in Darmstadt, Germany. PANDA will be a fixed target experiment designed for the study of non-perturbative phenomena of the strong interaction. Strange hyperon production is governed by m(s)  ~ 100 MeV, which corresponds to the confinement domain. Thus, hyperons are suitable probes in this energy region. This work is a simulation study focused on the feasibility of studying the production of Σ0-bar and Λ hyperons in the pbar p -> Σ0-bar Λ reaction with the PANDA detector. A 10^4 events sample simulated at p(beam) = 1.771 GeV/c is used to perform a single-tag (inclusive) and a double-tag (exclusive) event selection. From the former, it is concluded that the single-tag method does not provide with the clean signal required for spin observables extraction. In contrast, exclusive event selection provides with a signal reasonably clean from combinatorial background and completely clean from generic hadronic background events. A signal (Σ0-bar Λ) reconstruction efficiency of ε = 5.3 ± 0.2 % is obtained for exclusive event selection. The corresponding signal to background ratio is S/B(Total) ~ 6 and the significance value is ~ 21. In addition, an exclusive event selection is performed on a 10^4 events sample simulated at p_(beam) = 6 GeV/c. Almost all the generic hadronic background events are removed by the applied selection criteria. At this beam momentum, the obtained signal efficiency is ε = 6.1 ± 0.3%, the signal to total background ratio is S/B(Total) ~ 4 and the significance is ~22. Both efficiencies are smaller compared to a previous simulation study on this channel, but are large enough to enable a study of the exclusive production of the pbar p -> Σ0-bar Λ reaction at PANDA. The difference between the results of this thesis work and the previous work is attributed to the more realistic implementation of the signal production mechanism, as well as the detector and reconstruction algorithms.

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In 2003 the Belle collaboration announced the discovery of the X(3872) particle. This was confirmed shortly thereafter by the CDF, D0 and BaBar collaborations, and later by the LHCb collaboration. Based on the decay modes that have been observed to date, it is clear that this particle is a hadron, that is, a composite particle that experiences the strong nuclear force. The X(3872) was found within a family of well understood hadrons called charmonia. Interestingly, it is quite difficult to interpret the X(3872) as a charmonium state. For this reason it has been widely speculated that the X(3872) cannot be understood in terms of the quark model, unlike the vast majority of hadrons observed to date. Such hitherto unobserved particles are called exotic hadrons. Since the discovery of the X(3872), many similarly anomalous charmonium-like particles have been discovered. As would be expected, some unanticipated hadrons have also been found in the closely related bottomonium spectrum. These particles are collectively referred to as heavy quarkonium-like. Evidence is growing that at least some of these particles are exotic hadrons. If confirmed, this would have dramatic implications for our understanding of the strong nuclear force. A major experimental and theoretical effort is now underway in the field of hadron spectroscopy to determine the identities of the heavy quarkonium-like states. In order to investigate the possibility that some of these states could be exotic hadrons, theoretical calculations are needed to firmly establish their properties. One of the main arguments for the existence of exotic hadrons is that they are predicted by the fundamental theory of the strong interaction, Quantum Chromodynamics (QCD). Therefore it is desirable to predict the properties of exotic hadrons using a theoretical approach that is firmly based in QCD. One such method is QCD sum rules (QSR). The research presented here uses the QSR technique to study exotic hadrons. There are several themes in this work. First is the use of QSR to predict the masses of exotic hadrons that may exist among the heavy quarkonium-like states. The second theme is the application of sophisticated loop integration methods in order to obtain more complete theoretical results. These in turn can be extended to higher orders in the perturbative expansion in order to predict the properties of exotic hadrons more accurately. The third theme involves developing a renormalization methodology for these higher order calculations. This research has implications for the Y(3940), X(3872), Zc(3895), Yb(10890), Zb(10610) and Zb(10650) particles, thereby contributing to the ongoing effort to understand these and other heavy quarkonium-like states.

The production of the neutral strange particles Λ, Λ[bar] and K⁰_s at HERA has been studied with the ZEUS detector, using an integrated luminosity of 121pb^-1 . Differential cross-sections are measured in a High Q² DIS sample (Q² ≥ 25GeV²), a Low Q² DIS sample (5 ≤ Q² ≤ 25GeV² ) and a photoproduction sample. The photoproduction sample has Q² <= 1GeV² and at least two jets that satisfy E_T^jet > 5GeV and |η^jet| < 2.4. Cross-sections are measured as a function of the particle P_T and η, and additionally as a function of the event Q² and x in the DIS samples, and as a function of x_γ in the photoproduction sample. The DIS cross-sections are compared to the ARIADNE Monte Carlo, which broadly describes the data. The photoproduction cross-sections are compared to PYTHIA, where the agreement is less good, particularly at low x_γ. The baryon-antibaryon asymmetry, defined as (Λ-Λ[bar])/(Λ+Λ[bar]), is measured and always found to be consistent with zero, indicating little transfer of the Baryon Number from the beam proton to the Λ system in the detector region. The polarization of Λ and Λ[bar] is measured and also found to be always consistent with zero, indicating that there is no preferred frame in Λ production. The baryon-meson ratio (Λ + Λ[bar])/K⁰_s is studied, and is found to generally agree with ARIADNE in DIS, but give an excess over PYTHIA in photoproduction. The excess is particularly prominent at low x_γ in events with no clear jet structure. This is interpreted as hadron production in this region depending on a more-than-one-dimensional overlap of quark wave functions. An excess of strangeness in this region at low x_γ with no high E_T jets would be significant. It is investigated by taking the ratio of strange particles to charged tracks but no excess is seen.

Fragmentation is the process by which bare quarks dress themselves up as hadrons. Since we cannot get reliable calculations of this process using perturbative quantum chromodynamics, the fragmentation properties of quarks must be obtained empirically. We report on the signal extraction and relative transverse momentum (pT) spectrum determination that will lead to a high precision measurement of relative fragmentation fractions of b quarks into B hadrons, in 1.96 TeV pp&macr; collisions. Using 1.9 fb-1 of data taken with the CDF-II detector, we fully reconstruct 473 +/- 42 B0s&rarr;D-sp + , 15206 +/- 203 B0 &rarr; D-pi+, 1483 +/- 45 B0 &rarr; D*-pi + and 4444 +/- 297 L0b&rarr;L+ cp- candidate decays. In order to reduce systematic uncertainties, ratios of pT spectra are reported. We find that Bs and B0 mesons are produced with similar pT and &Lambda;b baryons are produced with lower pT than B0 mesons. Our results are consistent with previous CDF measurements suggesting a difference between fragmentation processes observed at lepton and hadron colliders.