Archive for the ‘physics’ Category

LHC Beam Transfer test

Wednesday, August 13th, 2008

the yellow spot indicates a bunch of protons arriving after traveling one eighth of the way around the Large Hadron Collider tunnel

the yellow spot indicates a bunch of protons arriving after traveling one eighth of the way around the Large Hadron Collider tunnel

Last weekend the Large Hadron Collider was tested by injecting a small number of protons into the beam line and steering them part way around the ring. Another test beam will be sent in the opposite direction on Aug. 22.

Zuoz Summer School

Monday, August 11th, 2008

the view of Zuoz from the Lyceum Alpinum

the view of Zuoz from the Lyceum Alpinum

I recently spent a week lecturing at a summer school in Zuoz Switzerland. This was finally my chance to stay at a Swiss Boarding School: the Lyceum Alpinum. My lectures were on strong interactions: Quantum Chromodynamics, Seiberg duality, the anti-de Sitter/conformal field theory correspondence and various models like quirks, higgsless, and hidden valleys, There were also lectures on black holes, little Higgs models, and the Large Hadron collider.  Slides of all the lectures can be found here.

CERN Rap

Wednesday, August 6th, 2008

CERN hasn’t really extended its public relations outreach to include rap videos, but a science writer at CERN, Kate McAlpine, has brought particle physics to the hip-hop masses.  The computer voice sounds like, but is not actually, Stephen Hawking.

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Lawrence Kraus Lecture

Tuesday, June 3rd, 2008

Lawrence Krauss

Lawrence Krauss

Lawrence Krauss gave a great HEFTI Lecture on Extra Dimensions at UC Davis.  The lecture was based largely on his recent book Hiding in the Mirror: The Mysterious Allure of Extra Dimensions.  He not only explained how mathematics led string theorists to extra dimensions he also delved into the psychology of why human beings like to believe in concepts like extra dimensions.

Gravitational Shockwaves

Thursday, May 17th, 2007

the path of a charged particle (blue) through the stationary field lines (red) of another charged particle

the path of a charged particle (blue) through the stationary field lines (red) of another charged particle

The winners of the annual Gravity Research Foundation essay competition were announced this week and the top two spots were swept by UC Davis. Steve Carlip won the $5000 first prize for his essay entitled “Symmetries, Horizons, and Black Hole Entropy”, while Nemanja Kaloper and yours truly took second place with How Black Holes Form in High Energy Collisions.  We looked at black hole formation following the analogous case of Coulomb scattering. Consider two charged particles colliding with one particle starting out at rest. As we increase the collision energy, the Coulomb field of the moving particle undergoes a relativistic compression, so that at velocities near the speed of light, the field lines are compressed into a shock wave.  Away from the shock wave there is essentially no scattering, everything happens as the rest particle crosses the shock wave.  The same thing happens in gravitational scattering, and the shock wave metrics for a highly boosted particle are well known.  If such a particle is approaching a second particle at rest, the the second particle is a tiny perturbation on the shock wave metric, so the calculation is very simple.  Even if the particle at rest crosses the shock wave at a large distance from the fast-moving particle the shock wave can scatter it almost directly towards the fast-moving particle so that they can pass within the Schwarzschild radius of the particle that started at rest.

the path of a charged particle (blue) through the moving field lines (red) of another charged particle

the path of a charged particle (blue) through the moving field lines (red) of another charged particle

the path of a charged particle (blue) through the very rapidly moving field lines (red) of another charged particle

the path of a charged particle (blue) through the very rapidly moving field lines (red) of another charged particle

Breaking Supersymmetry

Tuesday, May 15th, 2007

Nathan Seiberg

Nathan Seiberg

This week Nathan Seiberg of the Institute for Advanced Studies, Princeton gave the physics colloquium. You have probably heard his name in connection with the Seiberg-Witten theory (which revolutionized areas of both theoretical physics and mathematics), and from Seiberg duality (which gave us a new understanding of strongly coupled field theories).  His talk explained the cosmological and particle physics motivations for supersymmetry, and new ideas about how supersymmetry can be broken if the vacuum of spacetime is unstable.  You can see copies of his slides here.

a long-lived false vacuum

a long-lived false vacuum

Bubble Chamber Art

Thursday, February 8th, 2007

Bubble Chamber 1, by Lylie Fisher

Bubble Chamber 1, by Lylie Fisher

We had an interesting HEFTI public lecture that combined physics with art this week.    First Prof. Richard Lander gave a brief overview of the physics of bubble chamber experiments, and then artist Lylie Fisher displayed her series of bubble chamber paintings and discussed her inspiration for the work. This was the wolrd premiere public viewing of this series of paintings.  The next public viewing will be at Stanford on March 1, to be followed by visits to CERN and Fermilab.

pion in a bubble chamber (from Richard Lander's talk)

pion in a bubble chamber (from Richard Lander's talk)


West Coast LHC

Friday, December 15th, 2006

Postcard of tracks left by a jet (lower left cluster of pink lines) observed at CDF

Postcard of tracks left by a jet (lower left cluster of pink lines) observed at CDF

The latest installment of the West Coast LHC Meetings was held in Davis last week. The meetings are trying to prepare theorists (particularly those living on or near the West Coast) for the flood of data that will arrive from the Large Hadron Collider (LHC) which will run a test beam in 2007 and start full scale running in 2008. The main focus of the meeting was “jets”. when high energy quarks or gluons are produced in particle collisions they appear in the detector as a large spay of particles (called a jet).  Trying to relate the proerties of jets to the properties of the quarks and gluons is a big problem.  Most of the talks are available online.

a multi-jet event viewed through energy deposition along thedetector barrel (from Joey Huston's talk)

a multi-jet event viewed through energy deposition along thedetector barrel (from Joey Huston's talk)

Cosmic Landscape

Wednesday, October 18th, 2006

Lenny Susskind

Lenny Susskind

Leonard Susskind of Stanford gave a HEFTI public lecture, based on his book The Cosmic Landscape: String Theory and the Illusion of Intelligent Design at UC Davis on Oct 17.  About 400 people got an entertaining look at the “landscape” of universes allowed by string theory and how it might explain some of the apparent fine-tunings in nature that make life possible. “Lenny” (as he is affectionately known to almost all) was in high form, but also showed how he could be gentle with his critics.

Custodial Symmetry for Z coupling

Sunday, July 16th, 2006

Kaustubh Agashe

Kaustubh Agashe

Agashe, Contino, Da Rold, and Pomarol recently realized that assigning top and bottom quarks to different representations of  SU(2)_L \times SU(2)_R can protect the coupling of the Z to the left-handed bottom quark from non-standard model corrections. Typically extra dimensional models of electroweak symmetry breaking with low mass scales for the Kaluza-Klein modes have corrections of the order of 20-40% while measurements from LEP and SLAC require less than a 0.25% deviation from the standard model prediction. The left-handed top and bottom quarks in their models are in the (2,2) representation rather than the (2,1) so there is a heavy top and an exotic quark to look for.