Li, Wei2019-05-172019-05-172018-052018-04-19May 2018Tu, Zhoudunming. "Search for the anomalous chiral effects via charge-dependent azimuthal correlations in proton-nucleus and nucleus-nucleus collisions at the LHC." (2018) Diss., Rice University. <a href="https://hdl.handle.net/1911/105712">https://hdl.handle.net/1911/105712</a>.https://hdl.handle.net/1911/105712Searching for the chiral magnetic effect (CME) via the charge-dependent azimuthal correlations with respect to the reaction plane has been attempted in AuAu collisions at the top Relativistic Heavy-Ion Collider (RHIC) energy 200 GeV by the STAR Collaboration, and later in PbPb collisions at the Large Hadron Collider (LHC) energy 2.76 TeV by the ALICE Collaboration. The observation of the significant charge separation signal from the correlators was first believed to be consistent with a CME, where the strong initial magnetic field induced from the spectator protons can generate an electric current from the chirality imbalance in the chiral medium, and consequently lead to a charge separation effect for the final-state particles. One of the most important implications of searching for the CME, is to experimentally confirm the chiral symmetry restoration in heavy ion collisions at sufficiently high temperature. Taking a step further to the initial measurement of the CME, the STAR Collaboration at RHIC and the ALICE Collaboration at the LHC also measured the charge-dependent second-order Fourier coefficient as a function of event charge asymmetry, which has been found to be consistent with the scenario of a chiral magnetic wave (CMW), a long-wavelength collective excitation arising from the CME. However, the experimental results were later found to be qualitatively consistent with some non-CME correlations, which could be related to momentum conservation, local charge conservation coupled with anisotropy flow, and short-range correlations, e.g., jets and resonance decay. Due to the nature of the complicated background contribution in the conventional way of measuring the CME and CMW, the speculated background correlations have never been explicitly shown in the experimental data, which makes the question of whether there is an unambiguous CME signal a longstanding problem for the past decade. Motivated by the problem of the CME background, the work of this thesis is the first attempt of exploring the background correlation in the experimental data, with a novel idea of using the small collision systems. In a high-multiplicity pA collision, the magnetic field in the overlap region and its correlation with respect to the event plane angle, are expected to be much smaller than in AA collisions. On the other hand, the azimuthal anisotropies of the final-state particles have been well established in the recent studies at the LHC, where a clear evidence of collectivity that is similar to AA collisions has been observed. Therefore, the small collision systems, e.g., pA collisions, provide a perfect testing ground and baseline for searching the CME and its background correlations. In addition, new experimental strategies have been developed, e.g., correlators with respect to higher harmonics, and a stringent upper limit has been set on the possible CME signal at the LHC energy for both pA and AA collisions. The contribution to the CME and CMW searches from the work of this thesis is highly significant in the community, where the quantitative measurements not only explicitly show the presence of backgrounds and set an upper limit on the CME at the LHC, but also provide a series of new measurements for the lower energy search. With a better understanding of the background correlations and new experimental approaches, the CME signal might be discovered in the upcoming isobaric run using the STAR detector at RHIC energy.application/pdfengCopyright is held by the author, unless otherwise indicated. Permission to reuse, publish, or reproduce the work beyond the bounds of fair use or other exemptions to copyright law must be obtained from the copyright holder.heavy ion physicschiral anomalyThesis2019-05-17