MEASUREMENTS OF TRANSVERSE SPIN DEPENDENT DI-PION AZIMUTHAL CORRELATION ASYMMETRY AND UNPOLARIZED DI-PION CROSS-SECTION IN PROTON-PROTON COLLISIONS AT A CENTER-OF-MASS ENERGY OF 200 GeV AT STAR

The transversity distribution function, h₁^q(x), where $x$ is the longitudinal momentum fraction of the proton carried by quark $q$, encodes the proton's transverse spin structure at leading twist. Difficulties arise when extracting h₁^q(x) due to its chiral-odd nature. However, it can be coupled with a spin-dependent interference fragmentation function (FF), H₁^{\sphericalangle, h₁h₂}, in a dihadron (h₁h₂) production channel in polarized proton-proton (p^\uparrow p) collisions. The coupling of h₁^q(x) and H₁^{\sphericalangle, h₁h₂} produces an experimentally measurable azimuthal correlation asymmetry, A_UT, between the spin of the fragmenting quark and the final state dihadron. A model-independent extraction of transversity from these measurements relies on the knowledge of dihadron FFs, namely the unpolarized dihadron FFs, D₁^{h₁h₂/q(g)} for quarks, \emph{q} (gluons, \emph{g}). Extraction of these FFs requires measurements of the unpolarized dihadron cross-section in $pp$ collisions, which are urgently needed. In $pp$ collisions, the unpolarized cross-section measurement provides access to the D₁^h₁h₂ for both quarks and gluons. This thesis outlines the measurements of the \dipion azimuthal correlation asymmetry in the forward ($\eta > 0$) and backward ($\eta < 0$) pseudorapidity regions with respect to the polarized beam using the RHIC Run 2015 polarized $pp$ data and the measurement of the unpolarized \dipion cross-section in the invariant mass bins in the mid-pseudorapidity ($|\eta|<1$) region using the RHIC Run 2012 $pp$ data at $\sqrt{s}=200$ GeV. These data sets were collected at the STAR experiment. The STAR Time Projection Chamber (TPC), Barrel Electromagnetic Calorimeter (BEMC), and Time-of-Flight Detector (TOF) were used in conjunction to measure outgoing particle energy, tracking, and identification.

Grantor dc:publisher

Temple University. Libraries

Year dc:date.issued

2023

Author dc:creator

• Pokhrel, Babu Ram

Advisor dc:contributor.advisor

• Surrow, Bernd

Committee members dc:contributor.committeemember

• Metz, Andreas
• Napolitano, Jim
• Vossen, Anselm AV

• Particle physics
• Azimuthal correlation asymmetry
• Dihadron cross-section
• Dihadron fragmentation function
• Transversity

Statement dc:rights

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Licence dc:rights.uri

• http://rightsstatements.org/vocab/InC/1.0/

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/20.500.12613/9539

OAI identifier oai:identifier

oai:scholarshare.temple.edu:20.500.12613/9539