Rigorous fit to the peak region of the thrust distribution

We continue the work of Abbate et al. in [1], in which a factorization formula for the thrust distribution in electron-positron collisions was developed in the framework of soft-collinear effective theory. We extend the analysis of thrust to the peak region of the distribution, in which a nonperturbative soft function encoding the effects of large-angle soft gluon radiation plays a significant role. We write the soft function as an infinite sum of basis functions and use a truncated version in our calculations, allowing us to fit for the basis coefficients ci with all available thrust data from center-of-mass energies Q = 35 to 207 GeV. To characterize the soft function independently of a particular parameterization, we present fit results for its cumulant moments, denoted [Omega]1, up to i = 4. We compute experimental uncertainties from the fits and theory uncertainties using a random scan in the space of the undetermined parameters of the theory. Our approach significantly improves the fit in the peak region, reducing the minimum X2/d.o.f. value from to 5.29 using the best fit form the tail region without fitting basis functions, to 1.23 using five basis functions. We find [Omega]1 = 0.387 ± (0.003)exp ±(0.026)pert GeV, indicating that the peak region determines [Omega] with considerably more precision than the tail. For the second cumulant moment, we find [Omega]'2 = 0.032 ± (0.002)exp ± (0.011)pert GeV2 . We also estimate the third and fourth cumulant moments, obtaining [Omega]'3 = [3.5 ± (0.7)expt ±(2.3)pert] x 10- GeV 3 and [Omega]'4 = [-0.7 ± (3 .8)exp ± (11.9)pert] X 10-4 GeV4.

Department dc:contributor.department

Massachusetts Institute of Technology. Department of Physics.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2014

Author dc:creator

• Prouty. Jeffrey C

Advisor dc:contributor.advisor

• Iain Stewart.

• Physics.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/92695

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/92695