Physics Department, Princeton University

Despite the striking success of the Standard Model (SM), there are many unsolved problems such as the large hierarchy in energy scales, the presence of dark matter throughout the universe, and the origin of the many fundamental parameters. While in general we do not know what the relevant energy scale is for the solution of most of the above problems, the electroweak scale is pointing us to new phenomena at the TeV scale. 

The most direct experimental path to the understanding of such issues uses particles of the highest achievable energies. Following this path, the Princeton High Energy group is deeply involved with the Compact Muon Solenoid (CMS) experiment at the Large Hadron Collider at CERN. The Large Hadron Collider (LHC) is a particle accelerator which will probe the structure matter deeper than ever before. It switched on in Sep. 10 2008, and the first 3.5TeV collisions took place the 30th of March 2010. The success of the machine and the increase in luminosity is about to provide us with 7 million times collisions per second. Understanding what happens in these collisions is the key to the LHC's success. 

As part of my service work I am co-manager of the CMS Luminosity since 2007, A significant component of the LHC program consists of precision measurements that necessitate an accurate luminosity determination. A good understanding of the luminosity is critical to managing the systematic errors on these precision measurements, providing more stringent tests of the underlying theory. The calibration will ultimately depend on careful measurements of known cross sections such as the pp total cross section or the production rates for Ws and Zs. My Graduate student (Jeremy Werner) thesis will be the first to use the Inclusive Z boson rate as standard candle for LHC. However at the moment the normalization of the instantaneous luminosity is provided by the method developed by S. Van Der Meer at the ISR based on machine parameters to the physics experiments. Our group responsibility included the development and deployment of the forward calorimeter based luminosity monitor to CMS, currently the sole lumi monitor in CMS. In addition, we are in process of production of the Diamond Pixel Luminosity Telescopes (proposed by the Rutgers-Princeton consortium). To find more about the delivered/recorded luminosity find  CMS Public Lumi Page.

 LHC will allow to explore the SM higgs in entire the SM phase space and search for supersymmetric particles which are constituent of the most popular extension of the SM. Currently my group research interest is in Physics beyond the Standard Model that could manifest itself by observing highly collimated multiple leptons that result from the decay of a highly boosted resonance. We studies various models that become available in light of recent astrophysical observations by N. Arkani-Hamed et. al. The authors proposed a broad class of theories in which the annihilation of TeV scale dark matter in the galactic halo accounts for the anomalous excess of cosmic ray leptons.While this dark matter is probably inaccessible to colliders, it is accompanied by a GeV scale dark sector which couples, very weakly, to the standard model (SM). The dark sector states are relatively light and can be produced at high energy colliders, only to cascade decay through the dark sector and ultimately return to the visible sector as electrons, muons, and possibly pions. The outgoing leptons emerge in the detector as lepton jets. Our initial studies shows the feasibility of these searches in CMS and we are currently looking for topological signatures of prompt and non prompt lepton jets. Acknowledging the enormous discovery potential of LHC, its likely we are at the edge of a revolutionary time for the physics of fundamental particle we all waited for.

GradStudents: Jeremy Werner (Ph.D Sep 2011),Wenhan Zhu (Ph.D Dec 2011),Adam Hunt (graduating in July 2012), Tim Lou (2011-current)

Postdocs:John Jones(2007-2009), Nadia Adam(2007-2011),Paul Lujan(2010-current)Pratima Jindal(2012-current)