is a 12,500 metric ton all purpose detector that
is being prepared to study 7 or 14 TeV proton-proton collisions at the
CERN Large Hadron Collider (LHC).
The Standard Model of fundamental particles points to a mysterious
component of empty space which gives particles the property of
mass. It is called the Higgs particle or field.
The Higgs may not be alone, and a number of new fundamental particles
may be needed to explain the laws of physics.
The Higgs and other new particles are believed to be
too heavy to be created at previous accelerators directly.
However, the new LHC collider, with the CMS
detector, should be capable of producing and detecting them
Project on CMS Tracker Alignment
and Resonance Spin Analysis
This project is supported in part by the U.S. National Science Foundation
(grants 0644849, 0758083, 1100862) and Alfred P. Sloan Foundation.
"Spin & alignment" group members at JHU
There are research opportunities for new graduate and undergraduate students
as a summer project or during the academic year.
Contact Prof. Gritsan or other members of the
CMS group at JHU.
- Andrei Gritsan (PI of NSF grant 0644849, co-PI of NSF grant 1100862, since October 2005)
- Andrew Whitbeck (graduate student, on the project since June 2009)
- Sara Bolognesi (postdoctoral fellow, on the project since September 2011)
- Nhan Tran (graduate student, May 2006 - October 2011,
- Alessio Bonato (postdoctoral fellow, May 2008 - August 2011)
- Zijin Guo (postdoctoral fellow, on CMS project August 2007 - May 2011)
- Chung Khim Lae (postdoctoral fellow, November 2006 - January 2009)
Tracker Alignment Project Description
Modern silicon tracking detectors typically have a large
number of measuring sensors, and statistical methods can
be used to align individual sensors with respect to each other.
For CMS there are more than 15,000 sensors which need to be aligned.
The goal of the alignment procedure is to obtain six parameters
for each independent sensor, these being
the three spacial and three rotational parameters.
Since 2005 we developed new analysis and modeling techniques
and initiated improved procedures for the CMS
pixel detector optical survey measurements at FNAL.
We developed statistical methods for the alignment of thousands of silicon sensors
using the chisq from survey together with tracks
and demonstrating their performance within the CMS software
framework. Since 2007 we are working on alignment of the first
components of the CMS silicon tracker with cosmic tracks.
In 2008-2009, the PI was a convener of the CMS tracker alignment group.
In 2010-2011 Alessio Bonato is a convener.
Understanding the alignment of thousands
of silicon sensors, which track particle paths, is necessary
to a micron precision and becomes the decisive factor in
discovering of new particles.
Results presented at:
The 2009 Europhysics Conference on High Energy Physics in Krakow (July 2009)
3rd LHC alignment workshop in Geneva (June 2009)
2nd LHC alignment workshop in Geneva (June 2007)
1st LHC alignment workshop in Geneva (September 2006)
proceedings in CERN-2007-004]
Resonance Analysis Project Description
The group has developed the tools to disentangle
complicated angular structures in a broad range of models.
This allows analysis of the spin, parity, and fundamental couplings
of new particles which may be observed at the LHC, such as
signatures of Higgs field, extra dimensions, or new gauge bosons.
These studies start with analysis of the known Z boson to two leptons
and measure its fundamental couplings to matter by measuring the
weak-mixing angle, the only unknown parameter in the standard
model which determines the relative couplings. These techniques
have direct application to analysis of new potential resonances
decaying to two fermions. We have also developed techniques for
the search for more complicated di-boson decays of a Higgs or an
exotic particle, such as H->ZZ, with subsequent decay to two leptons
and two quark jets. This final state is complemented by the golden
mode of four leptons in the final state, and our angular analysis
provides powerful discrimination tool either against background
or among different hypotheses of new physics.
The program is designed to extract maximum information possible
with the available LHC data, which also provides the tightest
possible limit on any model to be excluded, including the
limits on the Higgs boson.
Results presented at:
JHU Physics and Astronomy colloquium (September 2011)
slides on The Heavy Invisible Light from the Large Hadron Collider
JHU particle physics seminar (August 2011)
slides on Searches for the Higgs boson with CMS at LHC]
15th Lomonosov Conference on Elementary Particle Physics in Moscow(August 2011)
slides on Searches for the Higgs boson with the CMS Experiment]
LHC Working Group on Precision Electroweak Measurements in Geneva (April 2011)
slides on Measurement of weak mixing angle at CMS]
MCTP Spring Symposium on Higgs Boson Physics at Ann Arbor, Michigan (May 2010)
slides on Spin Determination of Single-Produced Resonances at Hadron Colliders]
The Power of Spin Correlations: from B-decays to Higgs and Beyond at the LHC (April-May 2010)
seminars at [FNAL],
Spin determination of single-produced resonances at LHC (March 2010)
seminar at UMD/JHU]
See also a
developed at JHU for spin analysis of a resonance production and decay to a di-boson final state.