Off-campus UMass Amherst users: To download dissertations, please use the following link to log into our proxy server with your UMass Amherst user name and password.

Non-UMass Amherst users, please click the view more button below to purchase a copy of this dissertation from Proquest.

(Some titles may also be available free of charge in our Open Access Dissertation Collection, so please check there first.)

# Lambda polarization in exclusive and diffractive inclusive final states produced in proton-proton diffraction dissociation at 800 GeV/c

#### Abstract

We have measured the polarization of $\Lambda\sp\circ$'s produced in the diffraction dissociation process $p\ +\ p\ \to\ p\ +\ \Lambda\sp\circ\ +\ X$ at 800 GeV/c using two million diffractive inclusive and 58,000 exclusive $\Lambda\sp\circ$ events. The $\Lambda\sp\circ$ kinematic variables in our data sample only have weak correlations. For the diffractive inclusive sample, we have studied the dependence of the $\Lambda\sp\circ$ polarization on the following variables: (1) $\Lambda\sp\circ$transverse momentum; (2) $\Lambda\sp\circ$ Feynman x; (3) missing mass squared of the beam system; and (4) event charge multiplicity. Our diffractive inclusive results agree well with the existing world results on inclusive $\Lambda\sp\circ$ polarization. We do not see a strong dependence on the missing mass squared of the beam system or event charge multiplicity. For the exclusive sample, we have studied two fully reconstructed reactions of the form p + p $\to$ p + $\Lambda\sp\circ$ + $K\sp+$ + ($\pi\sp+\pi\sp-)\sp{n}$, n = 1, 2 and the topology dependence of the polarization. Within the statistical uncertainties, the $\Lambda\sp\circ$ polarization does not depend on the final state. Our results show that the $\Lambda\sp\circ$ polarization of the exclusive sample is consistently larger than that of the diffractive inclusive sample, although the uncertainties are large. The study using exclusive events enables us to account for all possible backgrounds and to minimize the dilution of $\Lambda\sp\circ$'s from $\Sigma\sp\circ$ decays and resonance productions. These analyses represent the first study of the $\Lambda\sp\circ$ polarization in diffraction dissociation at 800 GeV/c. It is also the first study of the topology, missing mass squared and event charge multiplicity dependence of $\Lambda\sp\circ$ polarization at this energy. ^

#### Subject Area

High energy physics

#### Recommended Citation

Lee, Shuyu, "Lambda polarization in exclusive and diffractive inclusive final states produced in proton-proton diffraction dissociation at 800 GeV/c" (1994). *Doctoral Dissertations Available from Proquest*. AAI9510495.

https://scholarworks.umass.edu/dissertations/AAI9510495