The Higgs boson has a new friend

[Update: Registration is now closed. Thank you to all of the interested photographers.]

Calling all photographers! Registration is now open for the 2018 Photowalk at the U.S. Department of Energy’s Fermi National Accelerator Laboratory.

On July 28, Fermilab will open its doors to 50 amateur and professional photographers for a four-hour behind-the-scenes Photowalk of the laboratory. Photographers will be able to visit, explore and take pictures of scientific machines and locations in research areas not usually accessible to the public.

The Fermilab Photowalk is part of the Global Physics Photowalk, hosted this summer at 16 labs around the world. This year’s event will feature labs and institutions in Australia, Europe and Asia as well as four (Fermilab, Brookhaven National Laboratory in New York, Sanford Underground Research Facility in South Dakota and SLAC National Accelerator Laboratory in California) in the United States.

The Global Physics Photowalk will draw from local and national competitions, with the winning national photos submitted to a global judging panel. The top three photos from Fermilab’s event, as chosen by a jury, will be submitted to the global competition organized by the Interactions collaboration.

Participation in the Fermilab Photowalk will be limited to the first 50 photographers to sign up online. Those who participated in the 2015 Photowalk at Fermilab will not be eligible for the 2018 event. Fermilab employees and users, and their families, are also ineligible.

Fermilab will maintain a waiting list to fill in any cancellations. The July 28 event is free of charge and will run from 8 a.m. to 12:30 p.m. For more information and to register online, please visit http://www.fnal.gov/pub/photowalk.

Fermilab is America’s premier national laboratory for particle physics and accelerator research. A U.S. Department of Energy Office of Science laboratory, Fermilab is located near Chicago, Illinois, and operated under contract by the Fermi Research Alliance LLC, a joint partnership between the University of Chicago and the Universities Research Association Inc. Visit Fermilab’s website at www.fnal.gov and follow us on Twitter at @Fermilab.

The DOE Office of Science is the single largest supporter of basic research in the physical sciences in the United States and is working to address some of the most pressing challenges of our time. For more information, please visit science.energy.gov.

The international Deep Underground Neutrino Experiment collaboration, hosted by the U.S. Department of Energy’s Fermilab, continues to grow. During the collaboration meeting at Fermilab from May 14-18, the DUNE Institutional Board admitted two new institutions to the collaboration: the Laboratory of Instrumentation and Experimental Particle Physics, which is the first institution from Portugal to join DUNE, and the University of Bucharest, the second institution from Romania. The collaboration now comprises 1,061 scientists from 175 institutions in 32 countries.

“The DUNE collaboration is growing at a rate of about 100 people per year,” said co-spokesperson Stefan Soldner-Rembold, professor at the University of Manchester in the UK. “About 60 percent of the 175 institutions on DUNE are from outside the United States.”

A substantial portion of the collaboration meeting was devoted to the upcoming operation of two DUNE prototype detectors at the European research center CERN, known as ProtoDUNE, with speakers presenting the updates on the construction happening this spring.

“There has been really remarkable progress,” said DUNE co-spokesperson Ed Blucher, professor at the University of Chicago. “Congratulations to the installation teams at CERN for their incredible efforts on the two ProtoDUNE detectors. Both are on track to collect data that will be important for finalizing the specifications of the liquid-argon detectors for the DUNE experiment.”

In addition to hosting the construction of the prototype detectors, CERN also will provide the cryostat for the first DUNE detector module to be installed at the Sanford Underground Research Laboratory in South Dakota, housed by the Long-Baseline Neutrino Facility that will be constructed at Fermilab and Sanford Lab.

“ProtoDUNE is a fundamental step towards many technological aspects of LBNF/DUNE,” said Marzio Nessi, leader of the CERN Neutrino Platform. “Before embarking on a multikiloton liquid-argon detector about 1.5 kilometers underground at Sanford Lab, we have to prove at the kiloton scale that we master the construction and operation of the large modular cryostats, that we are able to obtain the required purity of the liquid argon, and that we are able to keep the high-voltage electric field inside the detector at the nominal value, without discharges. ProtoDUNE is the first step, which will give us confidence that we are on the right track.”

Filling of the first prototype detector at CERN with liquid argon, known as single-phase ProtoDUNE detector, is anticipated to begin in June.

“Completion of the huge protoDUNE detector in little over two years from approval is an extraordinary achievement by groups on both sides of the Atlantic,” said ProtoDUNE co-leader Christos Touramanis, professor at the University of Liverpool in the UK. “It fills us with confidence that the ambitious DUNE construction schedule will be met.”

The first ProtoDUNE detector will start recording particle tracks later this year.

“It has been an incredible team effort bringing together the ProtoDUNE detector elements constructed in the U.S. and UK,” said ProtoDUNE Construction Coordinator Regina Rameika of Fermilab. “The support we have received from CERN for the installation has been amazing. We are now looking forward to operating the detector.”

The construction of the second prototype detector at CERN, known as the dual-phase ProtoDUNE detector, also is progressing well.

“In the last months, the progress in the construction and test of the various components of the second DUNE prototype detector at CERN has changed gear,” said Filippo Resnati, the technical coordinator of the Neutrino Platform at CERN. “The field cage is fully installed and has been tested at 150,000 volts. In June, the first 3-meter-by-3-meter signal-amplification system will be ready to be extensively tested in realistic thermodynamic conditions. Light readout, electronics, data acquisition and detector control systems are in very good shape too. The installation of the detector will be completed in fall of this year.”

Once it is operational, scientists will record cosmic-ray muons to test the detector.

“We are eagerly looking forward to the completion and the operation of the dual-phase ProtoDUNE detector,” said CNRS Research DIrector Dario Autiero of the French National Institute of Nuclear and Particle Physics. “The innovative design of this prototype is the outcome of a long R&D process. It is aimed at providing DUNE additional handles. The construction effort for this large-scale detector required a strong dedication from many groups and would not have been possible without the fundamental support from CERN.”

Another important topic at the collaboration meeting was the Interim Design Report for the construction of DUNE far detector modules in South Dakota. The document is based on the experience DUNE scientists and engineers gained during the design and construction of the prototype detectors at CERN. It is a step toward the publication of the more detailed Technical Design Report in 2019, which will serve as the blueprint for the construction of the first DUNE far detector modules.

“Within a few months, the recently formed DUNE Far Detector Institutional Consortia — who take responsibility for the construction, installation and commissioning of the different far detector subsystems — were able to provide detailed documentation on the current state of their planning efforts,” said Eric James, DUNE technical coordinator. “Production of the Interim Design Report on such a short time scale sends a strong signal that the collaboration remains on track to meet its goal of producing the Technical Design Reports for the first two far detector modules by spring 2019.”

DUNE now comprises institutions from 32 countries: Armenia, Brazil, Bulgaria, Canada, Chile, China, Colombia, Czech Republic, Finland, France, Greece, India, Iran, Italy, Japan, Madagascar, Mexico, Netherlands, Paraguay, Peru, Poland, Portugal, Romania, Russia, South Korea, Spain, Sweden, Switzerland, Turkey, Ukraine, United Kingdom, and United States. More information is at dunescience.org.

To learn more about the Deep Underground Neutrino Experiment, the Long-Baseline Neutrino Facility that will house the experiment, and the PIP-II particle accelerator project that will power the neutrino beam for the experiment, visit www.fnal.gov/pub/science/lbnf-dune/.

The Higgs field is like an endless ocean through which all matter swims. Some particles are like sponges and sop up mass as they lumber along, while others are as sprightly as tiny minnows and dart right through.

The Higgs theory is a beautifully simple explanation as to why some particles are massive while others are not. But not all predictions of the Higgs theory have been experimentally tested yet. That’s why scientists on the CMS experiment at the Large Hadron Collider are putting the Higgs boson under a microscope and trying to determine how it fits into the delicate ecosystem of particles.

“We know that the Higgs interacts with massive force-carrying particles, like the W boson, because that’s how we originally discovered it,” said scientist Patty McBride from the U.S. Department of Energy’s Fermi National Accelerator Laboratory, which supports the research of hundreds of U.S. scientists on the CMS experiment. “Now we’re trying to understand its relationship with fermions.”

Fermions are particles that click together to form the invisible scaffolding inside atoms. Bosons, on the other hand, are the physical manifestation of forces and perform tasks such as gluing fermions together.

In June 2014, scientists on the CMS experiment published a paper in Nature showing that the Higgs boson has a relationship with fermions by measuring the rate at which it decays into tau leptons, a heavier cousin of the electron. Later, both the CMS and ATLAS experiments found evidence of the Higgs boson decaying into bottom quarks. Now, scientists are tackling its relationship with the top quark.

“The relationship between the Higgs and the top quark is particularly interesting because the top quark is the most massive particle ever discovered,” McBride said. “As the ‘giver of mass,’ the Higgs boson should be enormously fond of the top quark.”

Because the top quark is much more massive than the Higgs boson, it’s impossible for a Higgs boson to decay into a pair of top quarks. Luckily, there is another way to measure how strongly the Higgs boson couples to top quarks: looking for the rare case of simultaneous production of top quarks and a Higgs boson.

“Higgs boson production is rare – but Higgs production with top quarks is rarest of them all, amounting to only about 1 percent of the Higgs boson events produced at the LHC,” said Chris Neu, a physicist at the University of Virginia who worked on this analysis.

In a paper published today in the journal Physical Review Letters, scientists on the CMS experiment report observing a statistically significant abundance of events in which the Higgs boson is produced in association with two top quarks. The CMS result for this rare Standard Model process with a significance of 5.2 sigma constitutes the first observation that exceeds the 5 sigma threshold physicists require. The ATLAS experiment has also submitted a paper on the same phenomenon for publication.

To get these results, the CMS experiment looked for Higgs bosons based on the numerous possible signatures it can leave behind in the detector.

“A top quark decays almost exclusively into a bottom quark and a W boson,” Neu said. “The Higgs boson, on the other hand, has a rich spectrum of decay modes, including decays to pairs of bottom quarks, W bosons, tau leptons, photons and several others. This leads to a wide variety of signatures in events with two top quarks and a Higgs boson. We pursued each of these and combined the results to produce our final analysis.”

Exploring the Higgs boson’s relationship with the top quark further could also be a possible window to new physics, according to Fermilab Deputy Director Joe Lykken.

“Pinning down this coupling will tell us a lot about the behavior of the Higgs and how it might also interact with other particles we haven’t discovered, like dark matter,” Lykken said. “Deeply understanding how the Higgs interacts with known particles could help lead us to physics beyond the Standard Model.”