Transverse Momentum Distributions of Hadrons
Transverse Momentum Distributions of Hadrons

Author:

Publisher:

Published: 1990

Total Pages: 14

ISBN-13:

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The study of hadron production in heavy ion collisions is essential to the search for effects beyond independent nucleon-nucleon collisions, for example the predicted phase transition to quark matter. Hadron distributions are known over a large range of transverse momenta for p-p collisions, so a careful study of the differences can be made. The transverse momentum distributions of hadrons may provide global information about p-nucleus and nucleus-nucleus collisions, such as the degree of thermalization achieved, and perhaps provide evidence for collective expansion of the highly excited central region. Comparison of the p{sub t} and transverse mass, m{sub t}, distributions of different hadronic species are crucial to extract this kind of information. Hadronic p{sub t} spectra show effects of the collision dynamics, such as hard scattering processes, and possibly rescattering of partons as well as of the formed hadrons. Such modifications have been observed in p-nucleus collisions, and can be expected to be important in nucleus-nucleus reactions. The spectral shape changes arising in this manner cause a background in efforts to extract global information from hadronic p{sub t} spectra. Lastly, there is an excess of pions observed at low p{sub t} in p-A and A-A collisions. the origin of these soft pions is not yet well understood. The phenomenon represents a major difference between p-p and nuclear collisions. 31 refs., 8 figs.

Relative Transverse Momentum Distributions of Bottom Hadrons Produced in 1.96 TeV Proton-antiproton Collisions
Relative Transverse Momentum Distributions of Bottom Hadrons Produced in 1.96 TeV Proton-antiproton Collisions

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Publisher:

Published: 2008

Total Pages: 109

ISBN-13:

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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 p{sub T} spectrum determination that will lead to a high precision measurement of relative fragmentation fractions of b quarks into B hadrons, in 1.96 TeV p{bar p} collisions. Using 1.9 fb−1 of data taken with the CDF-II detector, we fully reconstruct 473 ± 42 B{sub s}° → D{sub s}−?, 15206 ± 203 B° → D−?+, 1483 ± 45 B° → D*−?+ and 4444 ± 297?{sub b}° →?{sub c}+?− candidate decays. In order to reduce systematic uncertainties, ratios of p{sub T} spectra are reported. We find that B{sub s} and B° mesons are produced with similar p{sub T} and?{sub b} baryons are produced with lower p{sub T} than B° mesons. Our results are consistent with previous CDF measurements suggesting a difference between fragmentation processes observed at lepton and hadron colliders.

Phenomenology Of Ultra-relativistic Heavy-ion Collisions
Phenomenology Of Ultra-relativistic Heavy-ion Collisions

Author: Wojciech Florkowski

Publisher: World Scientific Publishing Company

Published: 2010-03-24

Total Pages: 437

ISBN-13: 9813107596

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This book gives an introduction to main ideas used in the physics of ultra-relativistic heavy-ion collisions. The links between basic theoretical concepts (discussed gradually from the elementary to more advanced level) and the results of experiments are outlined, so that experimentalists may learn more about the foundations of the models used by them to fit and interpret the data, while theoreticians may learn more about how different theoretical ideas are used in practical applications. The main task of the book is to collect the available information and establish a uniform picture of ultra-relativistic heavy-ion collisions. The properties of hot and dense matter implied by this picture are discussed comprehensively. In particular, the issues concerning the formation of the quark-gluon plasma in present and future heavy-ion experiments are addressed.

Transverse Spin Physics
Transverse Spin Physics

Author: Vincenzo Barone

Publisher: World Scientific

Published: 2003

Total Pages: 308

ISBN-13: 9812381015

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This book is devoted to the theory and phenomenology of transverse-spin effects in high-energy hadronic physics. Contrary to common past belief, it is now rather clear that such effects are far from irrelevant. A decade or so of intense theoretical work has shed much light on the subject and brought to surface an entire class of new phenomena, which now await thorough experimental investigation. Over the next few years a number of experiments world-wide (at BNL, CERN, DESY and JLAB) will run with transversely polarised beams and targets, providing data that will enrich our knowledge of the transverse-spin structure of hadrons. It is therefore timely to assess the state of the art, and this is the principal aim of the volume.An outline of the book is as follows. After a few introductory remarks (Chapter 1), attention is directed in Chapter 2 to transversely polarised deeply-inelastic scattering (DIS), which probes the transverse spin structure function 2. This existing data are reviewed and discussed (for completeness, a brief presentation of longitudinally polarised DIS is also provided). In Chapter 3 the transverse-spin structure of the proton is illustrated in detail, with emphasis on the transversity distribution and the twist-three parton distribution contributing to g2. Model calculations of these quantities are also presented. In Chapter 4, the QCD evolution of transversity is studied at leading and next-to-leading order. Chapter 5 illustrates the g2 structure function and its related sum rules within the framework of perturbative QCD. The last three chapters are devoted to the phenomenology of transversity, in the context of Drell-Yan processes (Chapter 6), inclusive leptoproduction (Chapter 7) and inclusive hadroproduction (Chapter 8). The interpretation of some recent single-spin asymmetry data is discussed and the prospects for future measurements are reviewed.

Studies on Hadron Structure Through Transverse Momentum Dependent Parton Distribution Functions
Studies on Hadron Structure Through Transverse Momentum Dependent Parton Distribution Functions

Author: Saman Bastami

Publisher:

Published: 2020

Total Pages: 0

ISBN-13:

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One of the main approaches toward understanding the hadronic structure is the introduction of transverse momentum dependent parton distribution functions (TMDs). These non-perturbative objects are accessible through deeply inelastic processes such as semi-inclusive deep inelastic scattering (SIDIS), Drell-Yan and e+e- annihilation. The current thesis explores the hadronic structure within the TMD approach under three independent chapters. As the first study in the present thesis the complete cross-section for the production of unpolarized hadrons in e-p semi-inclusive deep-inelastic scattering is computed up to power-suppressed O(1=Q2) terms, utilizing an approximation which systematically assumes that ̄qgq-terms are much smaller than ̄qq-correlators. All leading- and subleading-twist structure functions are calculated in terms of six TMDs and two fragmentation functions for which phenomenological extractions are available. The results are compared to available experimental data from COMPASS, HERMES and Jeerson Lab. p Drell-Yan process is the subject of the second study in this thesis. All leading-twist structure functions of -induced Drell-Yan with polarized protons are computed at the scale of COMPASS experiment. The non-perturbative inputs for the TMDs are taken from available phenomenological extractions plus two well-established models: The light-front constituent quark model and the spectator model. Evolution eects are estimated using a Gaussian ansatz with energy-dependent Gaussian widths. The results are compared to COMPASS data when available leading to important conclusions about pion and proton TMDs. Predictions are made for future experiments. The third study in this thesis aims at establishing a generalized covariant parton model that allows us to obtain all possible TMDs in a systematic way by describing the quark correlator in terms of two covariant distribution functions for on-shell partons. The proposed formulation of the model successfully reproduces all results of the original version of the model for the leading-twist time-reversal-even (T-even) TMDs and enables us to evaluate all T-even twist-3 TMDs for the first time. The unpolarized and helicity parton distribution functions are used as inputs and other TMDs are calculated then compared to available TMD parametrizations. The results show several model relations between the TMDs some of which are expected from QCD and some verified in other quark models as well.

Identified Particle Transverse Momentum Distributions from AU + AU Collisions at 62.4 GeV Per Nucleon Pair
Identified Particle Transverse Momentum Distributions from AU + AU Collisions at 62.4 GeV Per Nucleon Pair

Author: Conor Henderson

Publisher:

Published: 2005

Total Pages: 322

ISBN-13:

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Transverse momentum (PT) distributions for pions, kaons, protons and antiprotons have been measured near mid-rapidity for Au+Au collisions at sNN = 62.4 GeV using the PHOBOS detector at the Relativistic Heavy-Ion Collider (RHIC) in Brookhaven National Laboratory. Particle identification is performed using the PHOBOS Time-of-Flight plastic scintillator walls and specific energy loss in the multi-layer silicon Spectrometer, which is also used for track reconstruction and momentum-determination. The spectra are corrected for all detector-dependent effects, including feed-down from weak decays. At PT 3 GeV/c, protons are measured to be the dominant species of charged hadrons and scale much faster with respect to collision centrality than mesons. This behaviour at 62.4 GeV is found to be remarkably similar to that observed in Au+Au collisions at 200 GeV, an interesting observation which should serve as an important constraint on the various mechanisms which have been proposed to describe particle production over this PT range. Baryon stopping, the transport of baryon number from intial beam rapidity, is explored through the net proton (p - p) yields at mid-rapidity. These results fill a large gap between the SPS and higher RHIC energies and as such form an important set of data for comparing to models of baryon transport mechanisms.