Brazilian Physicists Join "Space LHC"
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reader!
It
follows an article published on day (09/02) in the english website of the Agência
FAPESP noting that Brazilian
Physicists join "Space LHC".
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NEWS
Brazilian Physicists Join "Space LHC"
By Elton
Alisson
September
02, 2015
(Image:
AMS-02)
The
performance of the AMS-02 particle detector is
comparable to that of the LHC at
CERN.
|
Agência
FAPESP – The Alpha
Magnetic Spectrometer (AMS-02), a particle detector that has been in service on
the International Space Station for the past four years, is comparable in
performance terms to CERN’s Large Hadron Collider (LHC) in Switzerland and can
be considered a “space version” of the LHC.
The University
of São Paulo’s São Carlos Physics Institute (IFSC-USP) in Brazil recently
joined the international collaboration that designed, built and operates the
AMS-02 and comprises more than 600 physicists affiliated with 56 research
institutions in 16 countries.
The inclusion
of IFSC-USP as the first South American institution to participate in the
international project was made possible by the project “Indirect dark matter search with the AMS-02 detector”,
supported by FAPESP under its Young Investigators Grants program.
The proposal
for collaboration between researchers at IFSC-USP and colleagues at France’s
Annecy-Le-Vieux Particle Physics Laboratory (LAPP-IN2P3-CNRS) to participate in
the AMS-02 project was also one of those selected in the second call for proposals of
FAPESP’s São Paulo
Researchers in International Collaboration (SPRINT) program.
“Our research
group will focus on the search for dark matter by measuring cosmic rays
detected by the AMS-02,” said Manuela Vecchi, a professor at IFSC-USP and
coordinator of the project.
The AMS-02 is
designed to measure the properties of cosmic rays, made up primarily of
high-energy particles traveling near the speed of light, such as protons,
electrons, positrons (the antiparticles of electrons) and antiprotons (the
antiparticles of protons), with the aim of contributing to a better
understanding of how the universe was formed.
High-precision
measurements of these cosmic rays’ compositions and fluxes could help determine
whether there is anything left in our galaxy of the primordial antimatter that
must have existed for the Big Bang to occur and the universe to be formed
almost 14 billion years ago, for example.
“We know that
at the very beginning the universe was probably made up of matter and
antimatter in equal proportions, but the part of the universe that has been
explored so far appears to consist mainly of matter,” Vecchi told Agência
FAPESP.
The antimatter
particles detected hitherto, such as positrons and antiprotons, are produced
together with matter particles in certain astrophysical processes, according to
Vecchi.
A detailed
analysis of the compositions and fluxes of cosmic rays using the AMS-02 may
enable researchers to identify potential exclusive sources of antimatter, which
could be antistars or antigalaxies. “No exclusive source of antimatter has ever
been found in the universe,” Vecchi said.
By measuring
the compositions and fluxes of antimatter particles like positrons and
antiprotons, the scientists will be able to study the presence of dark matter
in the galaxy. Dark matter, which neither emits nor absorbs electromagnetic
radiation, is thought to make up 25% of the universe, according to Vecchi.
“The
measurements already made by the AMS-02 and other detectors brought on stream
in recent years suggest there are more positrons in our galaxy than the number
expected from conventional astrophysical processes,” she said.
“That means
positrons are probably produced not just by conventional astrophysical
processes but also by other sources in our galaxy. We don’t yet know what these
are.”
One of the
hypotheses is that there are zones in space with high densities of dark matter,
which collide and mutually annihilate near the solar system.
Theoretical
models predict the production of a significant flux of positrons and
antiprotons during the process of dark matter annihilation. They also suggest
that antimatter particle fluxes can be detected because their energy spectrum
differs considerably from that of the particle fluxes from astrophysical
sources, Vecchi explained.
“One of the
AMS-02 collaboration’s goals is to understand the origin of positrons and
antiprotons,” she said. “It’s important to try to ascertain whether these
particles are really produced by astrophysical sources or result from the
annihilation of dark matter.”
Installation
in Space
According to
Vecchi, design and construction of the AMS-02 began over 15 years ago.
Before being
sent into space it was calibrated on CERN’s test beam, used for the LHC as well
as for other particle detectors.
It was then
sent to the United States, where NASA’s space shuttle Endeavor took it to the
International Space Station (ISS) in early 2011.
“The AMS-02 is
the first and only particle detector in operation on the ISS,” Vecchi said.
“Most of the
projects under way on the ISS have to do with biological research, such as
evaluating different life forms under microgravity conditions. The astronauts
living there also perform biological experiments on themselves.”
Data are
acquired by the AMS-02 approximately 700 times per second and are processed by
computers on the ISS and downloaded via NASA satellite to the experiment
control center at CERN.
“The
experiment control center, which controls the AMS-02 remotely, operates around
the clock every day of the year because the detector captures and transfers
data to Earth uninterruptedly,” Vecchi said.
The AMS-02
operates in space so that it can measure cosmic rays before the particles
interact with Earth’s atmosphere. Scientists study the rays’ compositions in
addition to looking for antimatter, given that positive and negative charges
can be distinguished, owing to the magnetic field produced by the detector.
“The AMS-02
can identify protons, helium nuclei, electrons, positrons, antiprotons and
heavier nuclei in cosmic rays,” she said.
There are
terrestrial cosmic ray observatories, such as the Pierre Auger Observatory, the
world’s largest facility for observing cosmic rays, installed near the town of
Malargüe in Mendoza Province, Argentina, approximately 1,200 km from Buenos
Aires (read more about the Pierre Auger Observatory at agencia.fapesp.br/20997).
However, the
Auger’s detectors identify secondary particles produced by cosmic rays
interacting with the atmosphere at energy levels above 100 billion billion
electronvolts, higher than those detected by the AMS-02.
“The
scientific objectives of the AMS-02 and Pierre Auger Observatory are different
but complementary,” Vecchi said.
“We believe
the cosmic rays detected by the AMS-02 are probably of galactic origin. To
study higher-energy cosmic rays from sources outside our galaxy, we need larger
detectors installed on Earth, like the Auger.”
The
Italian-born physicist has been a member of the AMS-02 Collaborations since
2011, when she was a postdoctoral research associate at CERN in Switzerland.
Source: English WebSite of the Agência FAPESP
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