Johns Hopkins University logo

Andrei Gritsan

my CMS activities

my BABAR activities

Overview of Research Activities

Particle physics is standing within reach of new discoveries. The undiscovered symmetries of nature which unify the fundamental forces and particles, the puzzle of dark matter and energy, and the apparent lack of antimatter in our Universe, all these mysteries are about to be uncovered at an unprecedented energy scale with the Large Hadron Collider. The discovery of new particles at the LHC will depend on the ability to distinguish their decay products from random particles produced in the high-energy collisions. An essential element of this is the alignment of thousands of silicon detectors that track the particles' paths which must be understood to micron precision. I am developing new procedures for alignment analysis of the CMS detector silicon tracking system and I am leading a group of physicists to perform alignment of more than 15000 silicon sensors. Later in 2008 we expect first highest-energy beam collisions at LHC and I preparing a program to search for new fundamental particles that would resolve the nature puzzles.

In the last several years while direct access to new fundamental particles was beyond the energy reach of operating accelerators, I have developed new ways to search for them via rare virtual loop decays. On the BABAR experiment, I targeted spin-correlation measurements in its decays to mesons with non-zero spin where new particles in virtual loops might cause different spin alignments. Prior to that on the CLEO experiment I discovered the first gluonic penguin loop decays via the observation of flavor changing neutral current process B->η'K. On BABAR, I discovered the B meson loop decays to two spin-one particles, such as B->φ K*, and developed techniques for their angular analysis. The result was a surprisingly large transverse polarization fraction, which contradicted all expectations and may become evidence for new particles and interactions. We are making a number of measurements that would resolve the puzzle.

An alternative indirect way to search for new effects is to constrain the Unitarity Triangle, which describes the only known source of CP violation but is believed to be insufficient to produce our matter-dominated Universe. One of the unconstrained angles of the Unitarity Triangle α was expected to be measured with B->ππ decays. However, I led a discovery of a new, more complicated decay B->ρρ and demonstrated that it gives the smallest uncertainty for the measurement of α. This discovery provided a determination of α with a precision that many believed could not be achieved. Recently we achieved a new breakthrough with the evidence for the all-neutral B->ρOρO decay and performed time-evolution measurements, which provide new insight to disentangle quantum effect ambiguities.

The above scientific questions shape the directions of my group. To read more about my CMS or BABAR activities, click on the CMS or BABAR links.