Contact Info

 


Carlo Dallapiccola
1038 Lederle Graduate Research Tower
University of Massachusetts
Amherst, MA 01003

Email: carlod@physics.umass.edu
CERN: carlo.dallapiccola@cern.ch
Phone: (413) 545-0994


Research

 

The ATLAS Experiment at the LHC

I currently spend most of my time working in two areas within the ATLAS collaboration: Analysis (TeV-Scale Gravity/Black Holes) and Muon Spectrometer Software.

TeV-Scale Gravity/Black Holes

One way to approach the hierarchy problem (the enormous gap between the fundamental scales of gravity (M_planck) and the other fundamental interactions (~1 TeV) is postulate that, in fact, there is but one fundamental scale: the electroweak scale around 100 - 1000 GeV. This would imply that gravitational interactions become strong at this same scale. In other words, M_planck is really only about 1 TeV. Such a scenario can be accomplished by assuming: (1) There are "large", compact submillimeter dimensions beyond the three with which we are familiar; (2) Only the graviton propagates in the extra dimensions (the "bulk") -- the Standard Model fields are localized on a 3-d "brane." In effect, at length scales larger than the extra dimensions gravity is "weak" (effective M_planck large) because of its "dilution" in the bulk.

An interesting consequence of these theories is that mini black holes may be created in the proton-proton collisions at the LHC, wherein the center-of-mass energy of parton collisions would be around the Planck scale. Indeed, it may be that black hole production would dominate the total cross section. Black holes with such small mass would have correspondingly high temperatures and decay rapidly via Hawking radiation (either evaporating completely or leaving behind some sort of remnant about which we currently know nothing). The Hawking radiation would be easy to detect in LHC experiments and would likely provide a relativly clean signature: plenty of high pt jets, photons and leptons, as well as large missing transverse energy (emission of neutrinos and gravitons) distributed isotropically. Currently I am working on a multivariate maximum likelihood method to use various observables to distinguish black hole events from other types of events and to measure the fundamental parameters (M_planck and number of extra dimensions).

Muon Spectrometer Software

The ATLAS detector includes a sophisticated muon spectrometer consisting of multiple stations of detectors (of four different technologies) and superconducting toroidal magnets that allows for very efficient detection of muons and momentum measurements for a large range of pt (a few GeV/c to hundreds of GeV/c). Detection of high pt leptons is a critical ingredient to a large number of analyses. I have focused on studies of contributions to "fake" missing Et from either missing muons or fake muons and on data-driven methods to measure the muon fake rate.

Other Projects

The BaBar Experiment

For most of the past decade, I've been working on measurements of CP violation in the B meson system, using data collected with the BaBar detector at SLAC. The PEP-II e+e- collider ran with asymmetric beam energies, creating B-Bbar pairs from Upsilon(4S) decay (the CM energy was chosen to be on the Upsilon(4S) resonance for most of the data-taking) with a boost of beta*gamma = 0.56 in the laboratory frame. This allowed for accurate measurements of the B decay times, which, in turn, allowed us to measure the time dependence of CP violation in B decays. My work has focused on using rare charmless B decays to pipi, Kpi and KK final states to measure sin(2alpha), where alpha if the angle at the apex of the "Unitarity Triangle." In the Standard Model, alpha is a measure of the relative phase difference between the CKM matrix elements Vtd and Vud (in the Wolfenstein convention).

Selected Publications and Talks