lundi 23 octobre 2017

ATLAS and CMS join forces to tackle top-quark asymmetry












CERN - European Organization for Nuclear Research logo.

Oct. 23, 2017

Event display of a tt̄ event candidate in the 2015 data (Image: ATLAS/CERN)

In their hunt for new particles and phenomena lurking in LHC collisions, the ATLAS and CMS experiments have joined forces to investigate the top quark. As the heaviest of all elementary particles, weighing almost as much as an atom of gold, the top quark is less well understood than its lighter siblings. With the promise of finding new physics hidden amongst the top quark’s antics, ATLAS and CMS have combined their top-quark data for the first time (link is external).

There were already hints that the top quark didn’t play by the rules in data collected at the Tevatron collider at Fermilab in the US (the same laboratory that discovered the particle in 1995). Around a decade ago, researchers found that, when produced in pairs from the Tevatron’s proton-antiproton collisions, top quarks tended to be emitted in the direction of the proton beam, while anti-tops aligned in the direction of the antiproton beam. A small forward-backward asymmetry is predicted by the Standard Model, but the data showed the measured asymmetry to be tantalisingly bigger than expected, potentially showing that new particles or forces are influencing top-quark pair production.

“As physicists, when we see something like this, we get excited,” says ATLAS researcher Frederic Deliot. If the asymmetry is much larger than predicted, it means “there could be lots of new physics to discover.”


Image above: All matter around us is made of elementary particles called quarks and leptons. Each group consists of six particles, which are related in pairs, or “generations” – the up quark and the down quark form the first, lightest and most stable generation, followed by the charm quark and strange quark, then the top quark and bottom (or beauty) quark, the heaviest and least stable generation. (Image: Daniel Dombinguez/CERN).

The forward-backward asymmetry measured at the Tevatron cannot be seen at the LHC because the LHC collides protons with protons, not antiprotons. But a related charge asymmetry, which causes top quarks to be produced preferentially in the centre of the LHC’s collisions, can be measured. The Standard Model predicts the effect to be small (around 1%) but, as with the forward-backward asymmetry, it could be made larger by new physics. The ATLAS and CMS experiments both measured the asymmetry by studying differences in the angular distributions of top quarks and antiquarks produced at the LHC at energies of 7 and 8 TeV.

Alas, individually and combined, their results show no deviation from the latest Standard Model calculations. These calculations have in fact recently been improved, and show that the predicted asymmetry is slightly higher than previously thought. This, along with improvements in data analysis, even brings the earlier Tevatron result into line with the Standard Model.

ATLAS and CMS will continue to subject the heavyweight top quark to tests at energies of 13 TeV to see if it deviates from its expected behaviour, including precision measurements of its mass and interactions with other Standard Model particles. But measuring the asymmetry will get even tougher, because the effect is predicted be half as big at a higher energy. “It’s going to be difficult,” says Deliot. “It will be possible to explore using the improved statistics at higher energy, but it is clear that the space for new physics has been severely restricted.”

The successful combination of the charge-asymmetry measurements was achieved within the LHC top-quark physics working group, where scientists from ATLAS and CMS and theory experts work together intensively towards improving the interplay between theory and the two experiments, explains CMS collaborator Thorsten Chwalek. "Although the combination of ATLAS and CMS charge asymmetry results didn't reveal any hints of new physics, the exercise of understanding all the correlations between the measurements was very important and paved the way for future ATLAS+CMS combinations in the top-quark sector.”

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

For more information:

Atlas webpage: http://atlas.cern/

CMS webpage: http://cms.cern/

ATLAS physics briefing: https://atlas.cern/updates/physics-briefing/studying-fragments-top-quark

Related links:

ATLAS: http://home.cern/abouts/experiments/atlas

CMS: http://home.cern/about/experiments/cms

For more information about European Organization for Nuclear Research (CERN), Visit: http://home.cern/

Images (mentioned), Text, Credits: CERN/Corinne Pralavorio.

Greetings, Orbiter.ch

Culmination of Spacewalks Leads into Studies on Crew Health and Performance












ISS - Expedition 53 Mission patch.

October 23, 2017

International Space Station (ISS). Animation Credit: NASA

After a trio of spacewalks this month, including the final one conducted last Friday by Commander Randy Bresnik and Flight Engineer Joe Acaba of NASA, the Expedition 53 crew returned to a schedule of full-time science this week.

Today, the crew explored how lighting aboard the International Space Station affects their performance and health. One such investigation is called Lighting Effects, which studies the impact of the change from fluorescent light bulbs to LEDs. By adjusting intensity and color, investigators on the ground will use crew feedback to determine if new lights can improve crew circadian rhythms, sleep and cognitive performance.


Image above: A spectacular aurora borealis, or “northern lights,” over Canada is sighted from the International Space Station near the highest point of its orbital path. Image Credit: NASA.

Blood and urine samples were also collected and stowed in the Minus Eighty Degree Celsius Laboratory Freezer for ISS, or MELFI, marking Flight Day 30 for the Biochemical Profile and Repository experiments. Specific proteins and chemicals in the samples are used as biomarkers, or indicators of health. Armed with a database of test results, scientists can learn more about how spaceflight changes the human body and protect future astronauts on a journey to Mars based on their findings.

Expedition 53 is also preparing a microsatellite carrying an optical imaging system payload for deployment. Its operation in low-Earth orbit will attempt to solidify the concept that these small satellites are viable investigative platforms that can support critical operations and host advanced payloads.

Related links:

Lighting Effects: https://www.nasa.gov/mission_pages/station/research/experiments/2279.html

Biochemical Profile: https://www.nasa.gov/mission_pages/station/research/experiments/1008.html

Repository: https://www.nasa.gov/mission_pages/station/research/experiments/981.html

Microsatellite carrying an optical imaging system payload: https://www.nasa.gov/mission_pages/station/research/experiments/2163.html

Expedition 53: https://www.nasa.gov/mission_pages/station/expeditions/expedition53/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Animation (mentioned), Image (mentioned), Text, Credits: NASA/Catherine Williams.

Best regards, Orbiter.ch

samedi 21 octobre 2017

Bigelow Aerospace and United Launch Alliance Announce Agreement to Place a B330 Habitat in Low Lunar Orbit








Bigelow Aerospace logo / United Launch Alliance (ULA) logo.

Oct. 21, 2017

Bigelow Aerospace and United Launch Alliance (ULA) are working together to launch a B330 expandable module on ULA’s Vulcan launch vehicle.  The launch would place a B330 outfitted module in Low Lunar Orbit by the end of 2022 to serve as a lunar depot.

B330 Habitat in Low Lunar Orbit

“We are excited to work with ULA on this lunar depot project,” said Robert Bigelow, president of Bigelow Aerospace. “Our lunar depot plan is a strong complement to other plans intended to eventually put people on Mars. It will provide NASA and America with an exciting and financially practical success opportunity that can be accomplished in the short term. This lunar depot could be deployed easily by 2022 to support the nation’s re-energized plans for returning to the Moon.

"This commercial lunar depot would provide anchorage for significant lunar business development in addition to offering NASA and other governments the Moon as a new exciting location to conduct long-term exploration and astronaut training.”

video
B330 A Fully Autonomous Stand -Alone Space Station description

The B330 would launch to Low Earth Orbit on a Vulcan 562 configuration rocket, the only commercial launch vehicle in development today with sufficient performance and a large enough payload fairing to carry the habitat. Once the B330 is in orbit, Bigelow Aerospace will outfit the habitat and demonstrate it is working properly.  Once the B330 is fully operational, ULA’s industry-unique distributed lift capability would be used to send the B330 to lunar orbit.  Distributed lift would also utilize two more Vulcan ACES launches, each carrying 35 tons of cryogenic propellant to low Earth orbit.  In LEO, all of the cryogenic propellant would be transferred to one of the Advanced Cryogenic Evolved Stage (ACES). The now full ACES would then rendezvous with the B330 and perform multiple maneuvers to deliver the B330 to its final position in Low Lunar Orbit.


Image above: Radiation Protection and Debris Shielding. Terrestrial test data and on-orbit validation suggest that a fully outfitted B330 spacecraft will have robust debris and radiation shielding.

“We are so pleased to be able to continue our relationship with Bigelow Aerospace,” said Tory Bruno, ULA’s president and CEO. “The company is doing such tremendous work in the area of habitats for visiting, living and working off our planet and we are thrilled to be the ride that enables that reality.”

Actual Bigelow module (BEAM) test on International Space Station

Bigelow Aerospace is a destination-oriented company with a focus on expandable systems for use in a variety of space applications.  These NASA heritage systems provide for greater volume, safety, opportunity and economy than the aluminum alternatives.

Launcher's, Modularity & Scalability (not to scale)

The B330 is a standalone commercial space station that can operate in low Earth orbit, cislunar space and beyond.  A single B330 is comparable to one third of the current pressurized volume of the entire International Space Station.  Bigelow Aerospace is developing two B330 commercial space station habitats that will be ready for launch any time after 2020.

Related links:

Bigelow Expandable Activity Module (BEAM): https://www.nasa.gov/content/bigelow-expandable-activity-module

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Commercial Space: http://www.nasa.gov/exploration/commercial/index.html

For more information on Bigelow Aerospace visit http://www.bigelowaerospace.com/

For more information on United Launch Alliance (ULA), visit the ULA website at http://www.ulalaunch.com/

Images, Videos, Text, Credits: ULA/Bigelow Aerospace/NASA.

Greetings, Orbiter.ch

vendredi 20 octobre 2017

Expedition 53 Spacewalk Successfully Comes to an End














ISS - Expedition 53 Mission patch / EVA - Extra Vehicular Activities patch.

October 20, 2017


Image above: Two NASA astronauts switched their spacesuits to battery power this morning at 7:47 a.m. EDT aboard the International Space Station to begin a spacewalk. Image Credit: NASA TV.

Expedition 53 Commander Randy Bresnik and Flight Engineer Joe Acaba of NASA completed a 6 hour, 49 minute spacewalk at 2:36 p.m. EDT. The two astronauts installed a new camera system on the Canadarm2 robotic arm’s latching end effector, an HD camera on the starboard truss of the station and replaced a fuse on the Dextre robotic arm extension.

video
Space Station Crew Completes a Trio of October Spacewalks

The duo worked quickly and were able to complete several “get ahead” tasks. Acaba greased the new end effector on the robotic arm. Bresnik installed a new radiator grapple bar. Bresnik completed prep work for one of two spare pump modules on separate stowage platforms to enable easier access for potential robotic replacement tasks in the future. He nearly finished prep work on the second, but that work will be completed by future spacewalkers.


Image above: The two astronauts installed a new camera system on the Canadarm2 robotic arm’s latching end effector. Image Credit: NASA TV.

This was the fifth spacewalk of Bresnik’s career (32 hours total spacewalking) and the third for Acaba (19 hours and 46 minutes total spacewalking). Space station crew members have conducted 205 spacewalks in support of assembly and maintenance of the orbiting laboratory. Spacewalkers have now spent a total of 53 days, 6 hours and 25 minutes working outside the station.

Related links:

Expedition 53: https://www.nasa.gov/mission_pages/station/expeditions/expedition53/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Images (mentioned), Video (NASA TV), Text, Credits: NASA/Melanie Whiting.

Best regards, Orbiter.ch

NASA's SDO Spots a Lunar Transit












NASA - Solar Dynamics Observatory (SDO) patch.

Oct. 20, 2017


On Oct. 19, 2017, the Moon photobombed NASA’s Solar Dynamics Observatory, or SDO, when it crossed the spacecraft’s view of the Sun, treating us to these shadowy images. The lunar transit lasted about 45 minutes, between 3:41 and 4:25 p.m. EDT, with the Moon covering about 26 percent of the Sun at the peak of its journey. The Moon’s shadow obstructs SDO’s otherwise constant view of the Sun, and the shadow’s edge is sharp and distinct, since the Moon has no atmosphere which would distort sunlight.

SDO captured these images in a wavelength of extreme ultraviolet light that shows solar material heated to more than 10 million degrees Fahrenheit. This kind of light is invisible to human eyes, but colorized here in green.

Solar Dynamics Observatory or SDO spacecraft. Image Credit: NASA

Related links:

Eclipses and Transits: https://www.nasa.gov/eclipse

SDO (Solar Dynamics Observatory): http://www.nasa.gov/mission_pages/sdo/main/index.html

Animation, Images Credits: NASA’s Goddard Space Flight Center/SDO/Joy Ng/Text: Lina Tran, NASA’s Goddard Space Flight Center, Greenbelt, Md.

Greetings, Orbiter.ch

NASA’s MAVEN Mission Finds Mars Has a Twisted Tail












NASA - MAVEN Mission logo.

Oct. 20, 2017

Mars has an invisible magnetic “tail” that is twisted by interaction with the solar wind, according to new research using data from NASA’s MAVEN spacecraft.

NASA’s Mars Atmosphere and Volatile Evolution Mission (MAVEN) spacecraft is in orbit around Mars gathering data on how the Red Planet lost much of its atmosphere and water, transforming from a world that could have supported life billions of years ago into a cold and inhospitable place today. The process that creates the twisted tail could also allow some of Mars’ already thin atmosphere to escape to space, according to the research team.

“We found that Mars’ magnetic tail, or magnetotail, is unique in the solar system,” said Gina DiBraccio of NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It’s not like the magnetotail found at Venus, a planet with no magnetic field of its own, nor is it like Earth’s, which is surrounded by its own internally generated magnetic field. Instead, it is a hybrid between the two.” DiBraccio is project scientist for MAVEN and is presenting this research at a press briefing Thursday, Oct. 19 at 12:15pm MDT during the 49th annual meeting of the American Astronomical Society’s Division for Planetary Sciences in Provo, Utah.

The team found that a process called “magnetic reconnection” must have a big role in creating the Martian magnetotail because, if reconnection were occurring, it would put the twist in the tail.


Image above: Artist's conception of the complex magnetic field environment at Mars. Yellow lines represent magnetic field lines from the Sun carried by the solar wind, blue lines represent Martian surface magnetic fields, white sparks are reconnection activity, and red lines are reconnected magnetic fields that link the surface to space via the Martian magnetotail. Image Credits: Anil Rao/Univ. of Colorado/MAVEN/NASA GSFC.

“Our model predicted that magnetic reconnection will cause the Martian magnetotail to twist 45 degrees from what’s expected based on the direction of the magnetic field carried by the solar wind,” said DiBraccio. “When we compared those predictions to MAVEN data on the directions of the Martian and solar wind magnetic fields, they were in very good agreement.”

Mars lost its global magnetic field billions of years ago and now just has remnant “fossil” magnetic fields embedded in certain regions of its surface. According to the new work, Mars’ magnetotail is formed when magnetic fields carried by the solar wind join with the magnetic fields embedded in the Martian surface in a process called magnetic reconnection. The solar wind is a stream of electrically conducting gas continuously blowing from the Sun’s surface into space at about one million miles (1.6 million kilometers) per hour. It carries magnetic fields from the Sun with it. If the solar wind field happens to be oriented in the opposite direction to a field in the Martian surface, the two fields join together in magnetic reconnection.

The magnetic reconnection process also might propel some of Mars’ atmosphere into space. Mars’ upper atmosphere has electrically charged particles (ions). Ions respond to electric and magnetic forces and flow along magnetic field lines. Since the Martian magnetotail is formed by linking surface magnetic fields to solar wind fields, ions in the Martian upper atmosphere have a pathway to space if they flow down the magnetotail. Like a stretched rubber band suddenly snapping to a new shape, magnetic reconnection also releases energy, which could actively propel ions in the Martian atmosphere down the magnetotail into space.

Since Mars has a patchwork of surface magnetic fields, scientists had suspected that the Martian magnetotail would be a complex hybrid between that of a planet with no magnetic field at all and that found behind a planet with a global magnetic field. Extensive MAVEN data on the Martian magnetic field allowed the team to be the first to confirm this. MAVEN’s orbit continually changes its orientation with respect to the Sun, allowing measurements to be made covering all of the regions surrounding Mars and building up a map of the magnetotail and its interaction with the solar wind.

Mars Atmosphere and Volatile Evolution or MAVEN spacecraft. Image Credit: NASA

Magnetic fields are invisible but their direction and strength can be measured by the magnetometer instrument on MAVEN, which the team used to make the observations. They plan to examine data from other instruments on MAVEN to see if escaping particles map to the same regions where they see reconnected magnetic fields to confirm that reconnection is contributing to Martian atmospheric loss and determine how significant it is. They also will gather more magnetometer data over the next few years to see how the various surface magnetic fields affect the tail as Mars rotates. This rotation, coupled with an ever-changing solar wind magnetic field, creates an extremely dynamic Martian magnetotail. “Mars is really complicated but really interesting at the same time,” said DiBraccio.

The research was funded by the MAVEN mission. MAVEN began its primary science mission on November 2014, and is the first spacecraft dedicated to understanding Mars’ upper atmosphere. MAVEN’s principal investigator is based at the University of Colorado’s Laboratory for Atmospheric and Space Physics, Boulder. The university provided two science instruments and leads science operations, as well as education and public outreach, for the mission. NASA Goddard manages the MAVEN project and provided two science instruments for the mission, including the magnetometer. Lockheed Martin built the spacecraft and is responsible for mission operations. The University of California at Berkeley’s Space Sciences Laboratory also provided four science instruments for the mission. NASA’s Jet Propulsion Laboratory in Pasadena, California, provides navigation and Deep Space Network support, as well as the Electra telecommunications relay hardware and operations.

MAVEN (Mars Atmosphere and Volatile Evolution): https://www.nasa.gov/mission_pages/maven/main/index.html

Images (mentioned), Text, Credits: NASA/Goddard Space Flight Center, Bill Steigerwald/Nancy Jones.

Greetings, Orbiter.ch

jeudi 19 octobre 2017

A more precise measurement for antimatter than for matter












CERN - European Organization for Nuclear Research logo.

19 Oct 2017


Image above: Stefan Ulmer, spokesperson of the BASE collaboration, working on the experiment set-up. (Image: Maximilien Brice, Julien Ordan/CERN).

This week, the BASE collaboration published, in Nature, a new measurement of the magnetic moment of the antiproton, with a precision exceeding that of the proton. Thanks to a new method involving simultaneous measurements made on two separately-trapped antiprotons in two Penning traps, BASE succeeded in breaking its own record presented last January. This new result improves by a factor 350 the precision of the previous measurement and allows to compare matter and antimatter with an unprecedented accuracy.

“This result is the culmination of many years of continuous research and development, and the successful completion of one of the most difficult measurements ever performed in a Penning trap instrument,” said BASE spokesperson Stefan Ulmer.

The results are consistent with the magnetic moments of the proton and antiproton being equal, with the experimental uncertainty of the new antiproton measurement now significantly smaller than that for protons. The magnetic moment of the antiproton is found to be 2.792 847 344 1 (measured in unit of nuclear magneton), to be compared to the figure of 2.792 847 350 that the same collaboration of researchers found for the proton in 2014, at the BASE companion experiment at Mainz, in Germany.

“It is probably the first time that physicists get a more precise measurement for antimatter than for matter, which demonstrates the extraordinary progress accomplished at CERN’s Antiproton Decelerator, ” added first-author of the study Christian Smorra.

video
The BASE experiment at CERN's Antimatter Factory

Video above: Drone footage of CERN's BASE experiment (Video:Noemi Caraban/CERN).

You can read the scientific paper here: http://doi.org/10.1038/nature24048

Note:

CERN, the European Organization for Nuclear Research, is one of the world’s largest and most respected centres for scientific research. Its business is fundamental physics, finding out what the Universe is made of and how it works. At CERN, the world’s largest and most complex scientific instruments are used to study the basic constituents of matter — the fundamental particles. By studying what happens when these particles collide, physicists learn about the laws of Nature.

The instruments used at CERN are particle accelerators and detectors. Accelerators boost beams of particles to high energies before they are made to collide with each other or with stationary targets. Detectors observe and record the results of these collisions.

Founded in 1954, the CERN Laboratory sits astride the Franco–Swiss border near Geneva. It was one of Europe’s first joint ventures and now has 22 Member States.

Related links:

BASE: http://home.cern/about/experiments/base

Antimatter: http://home.cern/topics/antimatter

For more information about European Organization for Nuclear Research (CERN), Visit: http://home.cern/

Image (mentioned), Video (mentioned), Text, Credits: CERN/Corinne Pralavorio.

Best regards, Orbiter.ch