A joint Fermilab/SLAC publication

june 2015dimensionsofparticlephysicssymmetry

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Table of contents

Breaking: LHC arrives at the next energy frontier

Signal to background: Japan’s next big neutrino project

Signal to background: Steady to a fault

Signal to background: The universe at your fingertips

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breaking

June 03, 2015

LHC arrives at the next energyfrontierData collection has officially begun at the Large Hadron Collider.By Katie Elyce Jones

Today the Large Hadron Collider began collecting data for the first time in two years.

The world’s most powerful particle accelerator powered back on in April and saw itsfirst record-energy collisions in May. Today it began colliding particles at a steady rate toprovide data for research.

This time around, the LHC is colliding particles at 13 trillion electronvolts, a 60 percentboost from its 2012 record of 8 TeV.

“Because we have higher energy, more particles are produced more frequently,” saysBeate Heinemann, ATLAS deputy spokesperson and physicist at the University ofCalifornia in Berkeley at Lawrence Berkeley National Laboratory. “We will be able to testtheories we’ve never been able to test before.”

Inside the LHC, highly energetic protons collide and briefly convert their energy tomass. This produces other particles. The higher the amount of energy in the collisions,the more massive the particles they can produce. Physicists discovered the Higgs bosonin 8 TeV collisions; there may be more to come at 13 TeV.

Notably, many scientists hope to discover Supersymmetry, a theoretical model thatpredicts more massive partner particles for each known fundamental particle.

Also on the roster of potential discoveries are dark matter particles. Scientists haveseen evidence that most of the matter in the Universe is dark matter, but they have neverknowingly produced it in the laboratory.

Scientists might even find something they don’t expect, says Jim Olsen, CMS physics

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co-coordinator and professor of physics at Princeton University. “It’s exciting to me thatin searching for things we have predicted, or we think might be there, we could findsomething completely unexpected.”

By increasing the energy and brightness of their particle beams, physicists aremultiplying their odds of detecting rare particle events. Particles and their decayprocesses might be bumped up by a factor of tens or hundreds. Scientists expect toproduce Higgs bosons more than twice as fast as before.

This is why scientists say we are now in the “precision era” of the Higgs boson. Themore Higgs bosons they can produce, the more precisely they can study their properties.

“By the end of 2015, the LHC could deliver the same amount of data on the Higgs aswe collected over 2011 and 2012 combined,” Olsen says. By the end of 2017, physicistscould be working with three to four times more Higgs data than was collected over thefirst run.

To take advantage of the upgraded accelerator, the ATLAS, ALICE, CMS and LHCbscientific collaborations made improvements to their detectors. Scientists have alsoupgraded the computing infrastructure that stores and disseminates the onslaught of datathe detectors collect.

Publications on 2015 data could begin rolling out as early as this fall, which couldinclude first analyses of searches for heavy particles. Olsen predicts that new Higgsboson results will likely be released by spring 2016.

If there are any groundbreaking, yet-to-be-foretold discoveries to be made, no oneknows where to pencil them in on the calendar. But many have optimistic outlooks forRun II.

“We have the best instrument we’ve ever had, and we’re going to look as hard aswe can,” Heinemann says. “If it can be found, we are going to find it.”

LHC restart timeline

February 2015

The Large Hadron Collider is now cooled to nearly its operational temperature.

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Info-Graphic by: Sandbox Studio, Chicago

LHC filled with liquid helium

The Large Hadron Collider is now cooled to nearly its operational temperature.

Read more…

A first set of superconducting magnets has passed the test and is ready for the LargeHadron Collider to restart in spring.

Info-Graphic by: Sandbox Studio, Chicago

First LHC magnets prepped for restart

A first set of superconducting magnets has passed the test and is ready for the Large

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Hadron Collider to restart in spring. Read more…

Engineers and technicians have begun to close experiments in preparation for thenext run.

Info-Graphic by: Sandbox Studio, Chicago

LHC experiments prep for restart

Engineers and technicians have begun to close experiments in preparation for the nextrun.Read more…

March 2015

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The Large Hadron Collider has overcome a technical hurdle and could restart as earlyas next week.

Info-Graphic by: Sandbox Studio, Chicago

LHC restart back on track

The Large Hadron Collider has overcome a technical hurdle and could restart as early asnext week. Read more…

April 2015

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The Large Hadron Collider has circulated the first protons, ending a two-yearshutdown.

Info-Graphic by: Sandbox Studio, Chicago

LHC sees first beams

The Large Hadron Collider has circulated the first protons, ending a two-year shutdown.

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Read more…

The Large Hadron Collider accelerated protons to the fastest speed ever attained onEarth.

Info-Graphic by: Sandbox Studio, Chicago

LHC breaks energy record

The Large Hadron Collider accelerated protons to the fastest speed ever attained onEarth.Read more…

May 2015

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LHC sees first low-energy collisions

Info-Graphic by: Sandbox Studio, Chicago

LHC sees first low-energy collisions

The Large Hadron Collider is back in the business of colliding particles.

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Read more…

The Large Hadron Collider broke its own record again in 13-trillion-electronvolt test collisions.

Info-Graphic by: Sandbox Studio, Chicago

LHC achieves record-energy collisions

The Large Hadron Collider broke its own record again in 13-trillion-electronvolt testcollisions.Read more…

June 2015

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Data collection has officially begun at the Large Hadron Collider.

Info-Graphic by: Sandbox Studio, Chicago

LHC arrives at the next energy frontier

Data collection has officially begun at the Large Hadron Collider.Read more…Like what you see? Sign up for a free subscription to symmetry!

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signal to background

June 09, 2015

Japan’s next big neutrino projectThe proposed Hyper-K experiment would dwarf its predecessor.By Glenn Roberts Jr.

In 1998, the Super-K detector in Japan revealed that ubiquitous, almost masslessparticles called neutrinos have the ability to morph from one type to another. Thatlandmark finding has become one of the most heavily cited scientific results in particlephysics.

Now scientists have proposed to build a successor to the still-operating Super-K: Hyper-K, a detector with an active volume 25 times its size.

Part microscope and part telescope, the proposed Hyper-K experiment could fill insome of the blanks in our understanding of our universe. It could help explain why theuniverse favors matter over antimatter. It could provide new details about the fluctuating“flavors” or types of neutrinos. It could help elucidate whether there is any differencebetween neutrinos and their anti-particles.

It could also provide a better understanding of dark matter and exploding stars andcould reveal whether protons—a main ingredient in all atoms—have an expiration date.

The proposed experiment would be complementary to DUNE, a planned long-baseline neutrino experiment in the United States that will use different technology.

The “K” in Super-K and Hyper-K stands for a play on the word Kamioka, the name ofa mountainous area about 200 miles west of Tokyo that houses multiple particle physicsexperiments.

“The uniqueness of Hyper-K is its size and resolution,” says Tsuyoshi Nakaya ofKyoto University, who leads the Hyper-K steering committee and has been a part ofSuper-K since 1999.

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The central component in the Hyper-K project would be a massive cylindrical tankmeasuring about 248 meters long and 54 meters high, filled with 1.1 million tons of highlypurified water. An alternate Hyper-K design calls for an egg-shaped tank.

Courtesy of: © Hyper-Kamiokande Collaboration

Hyper-K would consist of an array of photo-detectors that would measure flashes oflight produced in particle events and processes occurring in the tank. The mountainabove Hyper-K would help to shield the detectors from the “noise” of other particles suchas cosmic rays.

Hyper-K would study a beam of neutrinos produced at the Japan Proton AcceleratorResearch Complex about 180 miles away in Tokai, and it would be able to detectneutrinos produced even farther away in Earth’s atmosphere and beyond. Hyper-K couldalso detect particles produced in the decay of a proton, something scientists have yet tosee.

“The discovery of proton decays would be revolutionary,” says Masato Shiozawa,Hyper-K project leader who works at the Institute for Cosmic Ray Research in Japan.

Hyper-K has already won international support from institutions in 13 countries, withthe largest groups coming from Japan, the United Kingdom, the United States,Switzerland and Canada. In January the ICCR announced a cooperative agreement topursue Hyper-K with the Institute of Particle and Nuclear Studies in Japan’s High EnergyAccelerator Research Organization.

About 200 researchers are already working on the design of Hyper-K, and thecollaboration is still welcoming new members. They hope to begin construction in 2018.

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signal to background

June 05, 2015

Steady to a faultHow do accelerators survive in some of the most earthquake-proneregions on Earth?By Lauren Biron

Perhaps you’ve seen the trailer for San Andreas, a movie in which a massive quakerocks northern California, toppling skyscrapers and propelling a massive tsunami towardthe Golden Gate Bridge.

Just a kilometer from the San Andreas Fault sits SLAC National AcceleratorLaboratory, home to a painstakingly calibrated particle accelerator. Which may elicit thequestion: Why build there? Isn’t a tectonic warzone a tough place to do physics?

The answer, it turns out, is yes and no. SLAC sits on relatively good soil that doesn’tamplify ground movement, says Scott DeBarger, department head of mechanicalengineering for accelerators. And despite the location of the accelerator, the number ofmajor earthquakes centered nearby has been minimal. The most recent big quake wasthe 6.9-magnitude Loma Prieta earthquake in 1989, which displaced several portions ofthe laboratory site by about a centimeter and gave it a bit of a tilt.

“It was a lengthy process of going back and putting things back where they needed tobe,” says DeBarger, who was on site when the earthquake hit. But adjusting magnetsand accelerator components isn’t as big a deal as it might seem.

SLAC’s accelerator was installed with an alignment system that allows engineers toestablish a 3-kilometer straight line along the length of the tunnel. Using lenses and alaser beam inserted at one end, they can check how precisely any component along theline is situated.

Almost all of the magnets have adjustable supports under them, either handledmanually with wrenches or controlled precisely with motors. Sections of the accelerator

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are aligned to the submillimeter level—and some things, like the center of the quadrupolemagnets that focus the beam, are precise to within half the width of a human hair.

For safety, the accelerator components are designed to satisfy building requirementsthat other structures are beholden to, whether they’re coffee shops or skyscrapers. “Itbecomes one of the loads you design for,” DeBarger says. “Elements are specificallyplanned to resist horizontal and vertical loads” that come with earthquakes. And sincethey happen so infrequently, earthquakes aren’t even the major factor in design.

“You want the accelerator to be well positioned and stiff, so that during the regularoperation, normal vibrations don’t cause the components to shift all over the place,”DeBarger says. “Stiffness requirements are often more demanding than the strengthrequirements.”

If an earthquake happened while the accelerator was on, the magnets might moveand steer the beam outside its normal space.

“In such an event, our beam containment system would detect the mis-steered beamand shut off the accelerator,” DeBarger says. The accelerator is also shielded to preventany harmful radiation from escaping.

While most of the accelerator is built to withstand major earth motions, the rare pieceof scientific equipment is seismically isolated. SLAC’s fragile BaBar detector, whichoperated at the accelerator from 1999 to 2008, was designed to stay stationary duringearthquakes while the ground moved around it. Instead of building the entire detector toresist the forces associated with earthquakes, scientists chose to accommodate potentialground motion by providing break points for equipment that connected to the detector.

With a number of nearby faults and a major California earthquake predicted within thenext 30 years, SLAC has a response plan in place for when “The Big One” hits.

Should a major earthquake occur, teams will assess the condition of buildings andsystems. Then professionals will be brought in to stabilize things and fix what’s broken.That’s when people like DeBarger will worry about realigning rogue accelerator pieces byasking themselves, “What’s its position, and what position does it have to be in to run?”

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signal to background

June 04, 2015

The universe at your fingertipsRaw images from the DECam Legacy Survey’s new image archivewill appear online the day after they are taken.By Manuel Gnida

When it was time to celebrate the 20th anniversary of the Star Wars trilogy, directorGeorge Lucas was prompted by technological leaps in the filmmaking industry to producea digitally remastered special edition.

Today scientists of the DECam Legacy Survey released their own version of a specialedition. They published the first in a series of catalogs that offer an update to images ofthe night sky originally taken with the 15-year-old camera of the Sloan Digital Sky Survey.

In the spirit of the new information age, the survey will share frequent updates on itspublic website. With its Sky Viewer, users can explore the contents of the universe,whose busyness might surprise anyone accustomed to bland skies polluted by city lights.

Site visitors can choose whether they want to look at false-color images or theoreticalmodels of the sky, or see the difference between the two. The website also contains amap of dust emissions in the Milky Way based on data first reported in one of the mostcited journal articles of all astrophysics.

Similar exploration tools exist for the image archives of SDSS and the Hubbletelescope. However, these data became publicly available only after a period of restricteduse by a limited group of researchers.

“The Legacy Survey is unique in that it doesn’t have any proprietary restrictions,”says David Schlegel of Lawrence Berkeley National Laboratory, who initiated the newproject together with Arjun Dey, a staff astronomer at the National Optical AstronomyObservatory. “Raw images will appear the day after they were taken, and we plan onreleasing processed versions every three to six months.”

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The Legacy Survey’s image archive will eventually cover one third of the sky. Hopesare that it will serve scientists around the world in a multitude of studies, fromexplorations of the structure of our Milky Way galaxy to analyses of our universe’smysterious dark energy that accelerates the cosmic expansion.

Today’s data release is the outcome of the survey’s first observations with the520-megapixel Dark Energy Camera, or DECam, which is mounted on the Blancotelescope in Chile. Additional snapshots will be also taken with cameras of the Bok andMayall telescopes in Arizona. The experiments began last fall and will take place on atotal of over 500 nights spread out over three years.

Processing mixed-quality data from three different telescopes collected under varyingobservation conditions will be a big challenge for the scientists.

“Given the large area of the sky we want to cover and the limited experimental timewe have been assigned, we can only take three images of each part of the sky,” saysLegacy Survey member Dustin Lang of Carnegie Mellon University, who developed newimage processing techniques that describe the observations with theoretical models. “Weneed to make the most of our data, no matter whether the observation conditions aregood or bad on a given night.”

Researchers want to link the images of stars, galaxies and other cosmic objects tocomplementary information they collect with spectroscopy, the analysis of light emissions.This includes, for instance, redshifts that measure how fast objects are moving relative tous, information crucial for dark energy studies.

After three years are up, the Legacy Survey should live up to its name. Theinformation it gathers will live on as a guide for a new surveyor, the Dark EnergySpectroscopic Instrument, whose redshift measurements will chart the expansion historyof the universe over the last 10 billion years of cosmic time.

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