High Energy Physics

The world's most ambitious scientific experiment is buried 100 meters underground, straddling Switzerland and France.  A billion times every minute, the Large Hadron Collider (LHC) slams together protons, while four giant detectors watch closely.

 So how does the Large Hadron Collider work?  Why can slamming tiny particles into each other provide clues about the nature of all space and time?  What mysteries are physicists trying to solve with data from the LHC, and what is the Higgs anyway?  What might we learn next? How does the cutting edge of particle physics relate to the world around us, from the patterns of stars in the sky to the fact that they shine at all?

 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 

 
 


So how
does the Large Hadron Collider work?  Why
can slamming tiny particles into each other provide clues about the nature of
all space and time?  What mysteries are
physicists trying to solve with data from the LHC, and what is the Higgs
anyway?  What might we learn next? How
does the cutting edge of particle physics relate to the world around us, from
the patterns of stars in the sky to the fact that they shine at all?

We add a gravitational background lattice to the simplest holographic model of matter at finite density and calculate the optical conductivity. With the lattice, the zero frequency delta function found in previous calculations (resulting from translation invariance) is broadened and the DC conductivity is finite. The optical conductivity exhibits a Drude peak with a cross-over to power-law behavior at higher frequencies. Surprisingly, these results bear a strong resemblance to the properties of some of the cuprates.

Precision timepieces are marvels of human ingenuity. Over the past half-a-century, precision time-keeping has been carried out with atomic clocks. I will review a novel and rapidly developing class of atomic clocks, optical lattice clocks. At their projected accuracy level, these would neither lose nor gain a fraction of a second over estimated age of the Universe. In other words, if someone were to build such a clock at the Big Bang and if such a timepiece were to survive the 14 billion years, the clock would be off by no more than a mere second. What can we do with this new-found precision? How can we exploit this exquisite ability to listen carefully for probing new physics?

In the second part of my talk I will overview atomic searches for new physics beyond the Standard Model of elementary particles.  I will report on a refined analysis of table-top experiments on violation of mirror symmetry in atoms. This analysis sets new constraints on a hypothesized particle, the extra
Z-boson. Our raised bound on the Z' masses improves upon the Tevatron results and carves out a
lower-energy part of the discovery reach of the Large Hadron Collider.

A local renormalization group procedure is proposed where length scale is changed in spacetime dependent manner. Combining this scheme with an earlier observation that high energy modes in renormalization group play the role of dynamical sources for low energy modes at each scale, we provide a prescription to derive background independent holographic duals for field theories. From a first principle construction, it is shown that the holographic theory dual to a D-dimensional matrix field theory is a (D+1)-dimensional quantum theory of gravity coupled with matter fields of various spins.The (D+1)-dimensional diffeomorphism invariance is a consequence of the freedom to choose different local RG schemes.

A beautiful understanding of the smallness of the neutrino masses may be obtained via the seesaw mechanism, whereby one takes advantage of the key qualitative distinction between the neutrinos and the other fermions: right-handed neutrinos are gauge singlets, and may therefore have large Majorana masses. The standard seesaw mechanism, however, does not address the apparent lack of hierarchy in the neutrino masses compared to the quarks and charged leptons, nor the large leptonic mixing angles compared to the small angles of the CKM matrix. In this talk, I will show that the singlet nature of the right-handed neutrinos may be taken advantage of in one further way in order to solve these remaining problems: Unlike particles with gauge interactions, whose numbers are constrained by anomaly cancellation, the number of gauge singlet particles is essentially undetermined. If large numbers of gauge singlet fermions are present at high energies - as is suggested, for example, by various string constructions - then the effective low energy neutrino mass matrix may be determined as a sum over many distinct Yukawa couplings, with the largest ones being the most important. This can reduce hierarchy, and lead to large mixing angles. Assuming a statistical distribution of fundamental parameters, we will show that this scenario leads to a good fit to low energy phenomenology, with only a few qualitative assumptions guided by the known quark and lepton masses. The scenario leads to predictions of a normal hierarchy for the neutrino masses, and a value for the |m_ee| mass matrix element of about 1-6 meV.