Thursday, Oct. 18, 2012

Have a safe day!

Thursday, Oct. 18

2:30 p.m.
Theoretical Physics Seminar - Curia II
Speaker: Ahmed Ismail, SLAC National Accelerator Laboratory
Title: A Higgs but No Sparticles Yet: What it Means for the (p)MSSM

3:30 p.m.


Friday, Oct. 19

3:30 p.m.

4 p.m.
Joint Experimental-Theoretical Physics Seminar - One West
Speaker: Mark Williams, Lancaster University
Title: Probing Matter-Antimatter Asymmetry in the Universe Using Muons from B Meson Decays at DZero

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Wilson Hall Cafe

Thursday, Oct. 18

- Breakfast: Mexican omelet
- Cuban black beans
- Ranchero steak tacos
- Stuffed pork chops
- Smart cuisine: Brazilian beef chimichurri
- Turkey BLT panini
- Assorted pizza
- Buffalo chicken tender ranch salad

Wilson Hall Cafe Menu

Chez Leon

Friday, Oct. 19

Wednesday, Oct. 24
- Rouladen
- Egg noodles with dill
- Glazed carrots
- Apple walnut cake

Chez Leon Menu
Call x3524 to make your reservation.


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From symmetry

Bringing the universe into full focus

From supernova explosions to writhing tendrils of dark matter, visualizations give new life to models and theories. Image courtesy of Ralf Kaehler and Tom Abel (visualization); John Wise and Tom Abel (numeric simulation)

In a darkened barn in Sweden in 1941, astronomer Erik Holmberg constructed two identical sets of 37 light bulbs, arranged in rings, to study the effects of a close encounter by two passing galaxies.

Using a light sensor connected to a device that measured electric current, Holmberg carefully charted, by hand, gravitational effects in energy signatures as he moved the two sets of bulbs closer together, and noted the emergence of "spiral arm" patterns.

He correctly concluded that galaxies can cluster and merge together as a result of such close passages. The experiment demonstrated the power of simulations and visualizations in understanding complex astrophysical phenomena, even before the era of computing.

Flash forward more than 70 years, and Holmberg's light bulb galaxies spring to life in three-dimensional visualizations made possible by advances in programming, computing power, observational data, theory and a smattering of graphical artistry.

In a windowless room at the Kavli Institute for Particle Astrophysics and Cosmology, visitors wearing 3D glasses witness the grand gravitational interplay of two large galaxies passing in close proximity, their spiral arms swinging out like choreographed combatants. Then the galaxies collide in a burst of light, with the scattered bits circling back and joining a new, larger galaxy. The two-minute, highly detailed visualization encapsulates 2 billion years, incorporates 40 million particles, and plays out on a 123-inch screen, offering an immersive and interactive way to dial back the universe's clock and refine calculations about its progression by comparing the visualization with observations.

The film includes about 40,000 separate "time steps," strung together into a movie, and required the equivalent of about 200,000 computer processor hours—a measure of the amount of time it would take a single processor to complete the visualization—to complete.

Read more

Glenn Roberts Jr.

Photos of the Day

Cool as a coyote

A female coyote mills about the Main Injector berm on Friday. She eventually went off into the interior of the ring. Photo: Marty Murphy, AD
A male coyote lounges on the Main Injector Q227 emergency exit. Photo: Marty Murphy, AD
In the News

Scientists develop affordable way to generate medical isotopes

From Argonne National Laboratory, Oct. 15, 2012

Scientists at the U.S. Department of Energy's (DOE) Argonne National Laboratory have developed a safe and affordable way to ensure a reliable U.S. supply of certain medical isotopes. Although the invention is at a conceptual stage, it has the potential to provide critical medical diagnostic material for small regional hospitals.

Read more
In the News

New type of cosmic ray discovered after 100 years

From CNRS, Oct. 10, 2012

Using the European X-ray astronomy satellite XMM-Newton, researchers from CNRS and CEA have discovered a new source of cosmic rays. In the vicinity of the remarkable Arches cluster, near the center of the Milky Way, these particles are accelerated in the shock wave generated by tens of thousands of young stars moving at a speed of around 700,000 km/h. These cosmic rays produce a characteristic X-ray emission by interacting with the atoms in the surrounding gas. Their origin differs from that of the cosmic rays discovered exactly a hundred years ago by Victor Hess, which originate in the explosions of supernovae. The findings are published in the journal Astronomy & Astrophysics.

Read more
Result of the Week

Counting jets to constrain physics models

The number of jets that appear in an event at DZero can reveal important information about the strong force.

Take a look at any given proton-antiproton collision recorded at DZero and you're likely to spot a jet, but not the kind you'd find at an air show.

When a quark or a gluon is produced in a high-energy collision, it will turn into a spray of particles, called a jet, due to interactions with the strong force. This is the same force that binds quarks into protons, neutrons and many more exotic particles. By carefully counting the number of times that at least two jets were seen in DZero events and comparing that to the number of times that at least three jets were seen, we are able to better constrain models of the strong force by directly answering the question, "How often does a quark emit a gluon?"

It is difficult to calculate predictions of what jets might appear after a collision directly from the Standard Model. Instead, we use experimental data to constrain models of these interactions. One complication is that the proton itself is a bundle of quarks and gluons, and jet production is sensitive to the fraction of momentum that each of the proton's pieces carries. Studying the ratio of the three-or-more jet production rate to the two-or-more jet production rate allows the strong force to be probed while minimizing the impact of the inner workings of the colliding proton and antiproton.

A recent analysis at DZero studies this ratio of jet production rates and compares them to the predictions from the latest theoretical models. The ratio is determined as a function of the largest-momentum jet, and the analysis is repeated for various cutoff values for the lowest-momentum jet. While no deviation was observed from the theoretical prediction, this result places important constraints on the way jets are modeled, which will be important to further our understanding of the strong force.

Mike Cooke

These physicists made major contributions to this analysis.
These physicists are the main administrators for the DZero Linux cluster, a crucial component of the DZero computing infrastructure that facilitates data analysis.

Today's New Announcements

Master Substation power outage - Oct. 22

State-of-the-laboratory meetings - Oct. 25 and 26

Survey of God's promise through history - begins Oct. 30

Network outage; several services affected - today

NALWO Playgroup Halloween party - Oct. 26

Farewell symposium for Bruce Chrisman - Oct. 26

In the Footsteps of Django - Oct. 27

SciTech presents Masters of Lightning - Nov. 3

CSADay 2012 training opportunities - Nov. 6

Applications being accepted for Wilson Fellowship

Abri Credit Union - money just got cheaper

Argentine tango classes

Winter volleyball begins soon

Accelerate to a Healthy Lifestyle update

Mac users: upcoming changes to VPN client software

Professional development courses

Atrium work updates

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