Question: On what date did NASA scientists reported that hints of dark matter may have been detected by the "Alpha Magnetic Spectrometer"?
About the article "International Space Station", section "Scientific research".

Candidate passages:
The ISS provides a platform to conduct scientific research that cannot be performed in any other way.
While small unmanned spacecraft can provide platforms for zero gravity and exposure to space, space stations offer a long term environment where studies can be performed potentially for decades, combined with ready access by human researchers over periods that exceed the capabilities of manned spacecraft.
The Station simplifies individual experiments by eliminating the need for separate rocket launches and research staff.
The wide variety of research fields include astrobiology, astronomy, human research including space medicine and life sciences, physical sciences, materials science, space weather, and weather on Earth (meteorology).
Scientists on Earth have access to the crew's data and can modify experiments or launch new ones, benefits generally unavailable on unmanned spacecraft.
Crews fly expeditions of several months duration, providing approximately 160-man-hours a week of labour with a crew of 6.
Kibō is intended to accelerate Japan's progress in science and technology, gain new knowledge and apply it to such fields as industry and medicine.
To detect dark matter and answer other fundamental questions about our universe, engineers and scientists from all over the world built the Alpha Magnetic Spectrometer (AMS), which NASA compares to the Hubble telescope, and says could not be accommodated on a free flying satellite platform due in part to its power requirements and data bandwidth needs.
On 3 April 2013, NASA scientists reported that hints of dark matter may have been detected by the "Alpha Magnetic Spectrometer".
According to the scientists, "The first results from the space-borne Alpha Magnetic Spectrometer confirm an unexplained excess of high-energy positrons in Earth-bound cosmic rays.
"The space environment is hostile to life.
Unprotected presence in space is characterised by an intense radiation field (consisting primarily of protons and other subatomic charged particles from the solar wind, in addition to cosmic rays), high vacuum, extreme temperatures, and microgravity.
Some simple forms of life called extremophiles, including small invertebrates called tardigrades can survive in this environment in an extremely dry state called desiccation.
Medical research improves knowledge about the effects of long-term space exposure on the human body, including muscle atrophy, bone loss, and fluid shift.
This data will be used to determine whether lengthy human spaceflight and space colonisation are feasible.
As of 2006, data on bone loss and muscular atrophy suggest that there would be a significant risk of fractures and movement problems if astronauts landed on a planet after a lengthy interplanetary cruise, such as the six-month interval required to travel to Mars.
Medical studies are conducted aboard the ISS on behalf of the National Space Biomedical Research Institute (NSBRI).
Prominent among these is the Advanced Diagnostic Ultrasound in Microgravity study in which astronauts perform ultrasound scans under the guidance of remote experts.
The study considers the diagnosis and treatment of medical conditions in space.
Usually, there is no physician on board the ISS and diagnosis of medical conditions is a challenge.
It is anticipated that remotely guided ultrasound scans will have application on Earth in emergency and rural care situations where access to a trained physician is difficult.
The Alpha Magnetic Spectrometer (AMS) is a particle physics experiment that is mounted on the S3 truss segment.
The AMS is designed to search for dark matter and anti-matter.
Five hundred scientists from 56 different institutions and 16 countries participated in the development and construction of the AMS.
The Alpha Magnetic Spectrometer was delivered by the STS-134 crew. 
 3 April *A breakthrough is achieved in the production of hydrogen fuel, allowing large quantities to be extracted from any plant.
*A new study suggests that common cholesterol-reducing drugs may also prevent macular degeneration.
*NASA scientists report that hints of dark matter may have been detected by the Alpha Magnetic Spectrometer on the International Space Station.
According to the scientists, "the first results from the space-borne Alpha Magnetic Spectrometer confirm an unexplained excess of high-energy positrons in Earth-bound cosmic rays."
*NASA states that complex organic chemicals could arise on Titan, a moon of Saturn, based on studies simulating the atmosphere of Titan.
4 April *The discovery of the most distant supernova yet found is announced.
*Scientists construct a 3D printer which can create material very similar to human tissue.
*A new species of giant tarantula, "Poecilotheria rajaei", is formally described, having been discovered in Sri Lanka in 2009.
*American scientists announce that they have identified a number of genetic markers that are associated with an increased risk of Alzheimer's disease.
*A new camera system is developed that can generate high-resolution 3D images from up to a kilometre away.
7 April – A US startup company develops plant-derived proteins that can be used as a sustainable, environmentally friendly substitute for eggs in almost all food products.
9 April *At the 2013 Sea-Air-Space Exposition, American defense companies display prototypes of numerous advanced weapons technologies, including viable railguns, VTOL airships and grenade-sized reconnaissance robots.
*British researchers discover that a mutation of the gene BRCA2 increases both the risk and severity of prostate cancer in men, as well as being linked to hereditary breast cancer in women.
*Chinese scientists develop a carbon-based aerogel which they claim is the lightest material yet produced, with a density only slightly greater than that of air.
*Scientists state that climate change may cause a significant increase in air turbulence over the North Atlantic by 2050, potentially endangering passenger aircraft.
10 April *Stanford University researchers develop "CLARITY", a method of making brain tissue transparent using acrylamide, allowing brain structures to be studied in unprecedented detail without requiring extensive biopsies.
*Scientists develop the first objective method of measuring pain by directly studying the brains of patients.
*Scientists find that, by inhibiting the SEC24A gene, cholesterol levels in mice can be reduced by 45%, offering hope for an alternative or complementary therapy to statins.
11 April *International researchers discover key similarities in the brains of arthropods and vertebrates, potentially aiding scientific understanding of the causes of human neural diseases.
*Philips demonstrates a new type of LED lighting that is reportedly twice as energy-efficient as any previous electric lightbulb.
*A study finds that carefully timed sounds played during sleep can enhance memory.
*NASA reports the possible finding of the "" of the 1971 Soviet Mars 3 lander on the planet Mars.
Images taken by the HiRISE camera on the Mars Reconnaissance Orbiter seem to show the possible remains of the parachute, retrorockets, heat shield and lander.
12 April *Animal trials are set to begin on a gene therapy for amyotrophic lateral sclerosis – a degenerative condition which counts Stephen Hawking among its sufferers.
*Scientists reconstruct the skeleton of the ancient hominid "Australopithecus sediba", discovering that it possessed a unique mixture of human- and ape-like traits.
*The first building to be entirely powered by algae is constructed in Hamburg.
15 April *A functional lab-grown kidney is successfully transplanted into a live rat in Massachusetts General Hospital.
This breakthrough is a major step forward for the nascent field of regenerative medicine.
*The Cryogenic Dark Matter Search experiment reports the possible discovery of traces of dark matter, although further experimental confirmation is required.
16 April – American medical researchers develop a new type of bandage which uses microscopic needles to adhere to injured flesh.
The bandage requires no adhesive chemicals, is significantly stronger than existing medical adhesives, and could offer a safer and more efficient means of securing skin grafts.
17 April *Scientists develop a new form of lithium-ion battery which is thousands of times more powerful than current battery technologies, while also charging much faster.
The battery utilises a compact 3D design, intertwining its electrodes to maximize its surface area while reducing its volume.
*MIT researchers determine the structure of bones down to the molecular level, using supercomputer simulations twinned with studies of real bone fibers.
Their data grants new insights into the compounds that grant living bone its strength, and may permit the manufacture of versatile new biomimetic materials.
*The genome of the coelacanth, an endangered deep-sea "living fossil", is sequenced.
18 April – NASA announces the discovery of three new Earthlike exoplanets – Kepler-62e, Kepler-62f, and Kepler-69c – in the habitable zones of their respective host stars, Kepler-62 and Kepler-69.
The new exoplanets, which are considered prime candidates for possessing liquid water and thus potentially life, were identified using the "Kepler" spacecraft.
21 April *The Antares rocket, a commercial launch vehicle developed by Orbital Sciences Corporation, successfully conducts its maiden flight.
*A study concludes that stress leads to faster growth in squirrels.
22 April *Biologists use antibodies to transform bone marrow stem cells directly into healthy brain cells.
This breakthrough may allow neurological injuries and illnesses to be more effectively treated, and reduces the risk of immune rejection.
*University of Exeter scientists report the creation of a genetically modified strain of "E. coli" bacteria which can convert sugar into diesel fuel.
*A British engineer unveils a giant "mantis" robot, large enough to carry a human pilot, which is supported by multiple hydraulic legs.
The robot has reportedly attracted the interest of mining and marine research companies.
24 April *IBM develops a robot which combines telepresence and augmented reality technologies to assist engineers working on complex projects in remote areas.
*CERN releases new particle-collision data from the Large Hadron Collider which may help explain why matter became dominant over antimatter in the early universe.
25 April – A partial lunar eclipse occurs.
26 April *Following laboratory tests of molten iron, European scientists determine that the Earth's core has a temperature of 6,000 degrees Celsius, 1,000 degrees hotter than previously thought.
This discovery may help explain why the planet has such a strong geomagnetic field.
*US and Chinese scientists develop a sensor array which is as sensitive to touch and pressure as the human fingertip.
The invention may pave the way for new robotic sensors, electronic interfaces and types of artificial skin.
27 April – Design approval is given for a crucial reactor component of the ITER nuclear fusion project, which is currently under construction in Cadarache, France, and is expected to begin generating fusion power in 2022.
29 April *After years of unpowered glide tests, Scaled Composites' SpaceShipTwo hybrid spaceplane successfully conducts its first rocket-powered flight.
*The ESA's Herschel Space Observatory runs out of liquid helium coolant, marking the end of its highly productive four-year mission to observe the far infrared universe.
*NASA's Cassini spacecraft photographs an enormous hurricane on Saturn, more than 20 times the size of the average terrestrial hurricane.
*NASA-funded French scientists claim that, during experiments on the International Space Station, microbes seem to adapt to the space environment in ways "not observed on Earth" and in ways that "can lead to increases in growth and virulence".  
Indirect detection experiments search for the products of WIMP annihilation or decay.
If WIMPs are Majorana particles (WIMPs are their own antiparticle) then two WIMPs could annihilate to produce gamma rays or Standard Model particle-antiparticle pairs.
Additionally, if the WIMP is unstable, WIMPs could decay into standard model particles.
These processes could be detected indirectly through an excess of gamma rays, antiprotons or positrons emanating from regions of high dark matter density.
The detection of such a signal is not conclusive evidence for dark matter, as the production of gamma rays from other sources is not fully understood.
The EGRET gamma ray telescope observed more gamma rays than expected from the Milky Way, but scientists concluded that this was most likely due to a mis-estimation of the telescope's sensitivity.
The Fermi Gamma-ray Space Telescope, launched 11 June 2008, is searching for gamma rays from dark matter annihilation and decay.
In April 2012, an analysis of previously available data from its Large Area Telescope instrument produced strong statistical evidence of a 130 GeV line in the gamma radiation coming from the center of the Milky Way.
At the time, WIMP annihilation was the most probable explanation for that line.
At higher energies, ground-based gamma-ray telescopes have set limits on the annihilation of dark matter in dwarf spheroidal galaxies and in clusters of galaxies.
The PAMELA experiment (launched 2006) has detected a larger number of positrons than expected.
These extra positrons could be produced by dark matter annihilation, but may also come from pulsars.
No excess of anti-protons has been observed.
The Alpha Magnetic Spectrometer on the International Space Station is designed to directly measure the fraction of cosmic rays which are positrons.
The first results, published in April 2013, indicate an excess of high-energy cosmic rays which could potentially be due to annihilation of dark matter.
A few of the WIMPs passing through the Sun or Earth may scatter off atoms and lose energy.
This way a large population of WIMPs may accumulate at the center of these bodies, increasing the chance that two will collide and annihilate.
This could produce a distinctive signal in the form of high-energy neutrinos originating from the center of the Sun or Earth.
It is generally considered that the detection of such a signal would be the strongest indirect proof of WIMP dark matter.
High-energy neutrino telescopes such as AMANDA, IceCube and ANTARES are searching for this signal.WIMP annihilation from the Milky Way Galaxy as a whole may also be detected in the form of various annihilation products.
The Galactic center is a particularly good place to look because the density of dark matter may be very high there.
In 2014, two independent and separate groups, one led by the Leiden astrophysicist Alexey Boyarsky and another from Harvard reported an unidentified X-ray emission line around 3.5 keV in the spectra of clusters of galaxies; it is possible this could an indirect signal from dark matter and that it could be a new particle, a sterile neutrino which has mass.  
Mission payload.
Alpha Magnetic Spectrometer 2.
The Alpha Magnetic Spectrometer 2 (AMS-02) was carried to the ISS in "Endeavour"'s payload bay, and was attached to the ISS's S3 truss segment.
The AMS-02 unit is a particle physics detector which contains a large permanent magnet, and is designed to search for antimatter and investigate the origin and structure of dark matter.
According to the original design plan, a cryogenic, superconducting magnet system was developed for the AMS-02.
This was reported by NASA to be a critical technology, granting the instrument the high sensitivity needed to achieve mission objectives.
Late in its development, however, poorly understood anomalous heating in the cryogenic magnet system was discovered.
As a result, the AMS-02 experiment leader, Samuel C. C. Ting, decided to replace the superconducting magnet inside the spectrometer with the permanent magnet previously used in AMS-01.