Italian newspaper "La Repubblica" on the OPERA presentation:
Press release CERN:
OPERA presents its final results on neutrino oscillations
The OPERA experiment, located at the Gran Sasso Laboratory of the Italian National Institute for Nuclear Physics (INFN), was designed to conclusively prove that muon-neutrinos can convert to tau-neutrinos, through a process called neutrino oscillation, whose discovery was awarded the 2015 Nobel Physics Prize. In a paper published today in the journal Physical Review Letters, the OPERA collaboration reports the observation of a total of 10 candidate events for a muon to tau-neutrino conversion, in what are the very final results of the experiment. This demonstrates unambiguously that muon neutrinos oscillate into tau neutrinos on their way from CERN, where muon neutrinos were produced, to the Gran Sasso Laboratory 730 km away, where OPERA detected the ten tau neutrino candidates.
Today the OPERA collaboration has also made their data public through the CERN Open Data Portal http://opendata.cern.ch/search?page=1&size=20&experiment=OPERA
By releasing the data into the public domain, researchers outside the OPERA Collaboration have the opportunity to conduct novel research with them. The datasets provided come with rich context information to help interpret the data, also for educational use. A visualiser enables users to see the different events and download them. This is the first non-LHC data release through the CERN Open Data portal, a service launched in 2014.
There are three kinds of neutrinos in nature: electron, muon and tau neutrinos. They can be distinguished by the property that, when interacting with matter, they typically convert into the electrically charged lepton carrying their name: electron, muon and tau leptons. It is these leptons that are seen by detectors, such as the OPERA detector, unique in its capability of observing all three. Experiments carried out around the turn of the millennium showed that muon neutrinos, after travelling long distances, create fewer muons than expected, when interacting with a detector. This suggested that muon neutrinos were oscillating into other types of neutrinos. Since there was no change in the number of detected electrons, physicists suggested that muon neutrinos were primarily oscillating into tau neutrinos. This has now been unambiguously confirmed by OPERA, through the direct observation of tau neutrinos appearing hundreds of kilometres away from the muon neutrino source. The clarification of the oscillation patterns of neutrinos sheds light on some of the properties of these mysterious particles, such as their mass.
The OPERA collaboration observed the first tau-lepton event (evidence of muon-neutrino oscillation) in 2010, followed by four additional events reported between 2012 and 2015, when the discovery of tau neutrino appearance was first assessed. Thanks to a new analysis strategy applied to the full data sample collected between 2008 and 2012 – the period of neutrino production – a total of 10 candidate events have now been identified, with an extremely high level of significance.
“We have analysed everything with a completely new strategy, taking into account the peculiar features of the events,” said Giovanni De Lellis Spokesperson for the OPERA collaboration. “We also report the first direct observation of the tau neutrino lepton number, the parameter that discriminates neutrinos from their antimatter counterpart, antineutrinos. It is extremely gratifying to see today that our legacy results largely exceed the level of confidence we had envisaged in the experiment proposal.”
Beyond the contribution of the experiment to a better understanding of the way neutrinos behave, the development of new technologies is also part of the legacy of OPERA. The collaboration was the first to develop fully automated, high-speed readout technologies with sub-micrometric accuracy, which pioneered the large-scale use of the so-called nuclear emulsion films to record particle tracks. Nuclear emulsion technology finds applications in a wide range of other scientific areas from dark matter search to volcano and glacier investigation. It is also applied to optimise the hadron therapy for cancer treatment and was recently used to map out the interior of the Great Pyramid, one of the oldest and largest monuments on Earth, built during the dynasty of the pharaoh Khufu, also known as Cheops.
Please note that the event "G. De Lellis - Final results of the OPERA experiment on nu_tau appearance in the CNGS neutrino beam" will start on Tuesday 22 May 2018 at 16:00 (Europe/Rome).
Location: LNGS (E. Fermi conference hall)
You can access the full event here:
A new paper of the Collaboration
"Final results of the OPERA experiment on ντ appearance in the CNGS beam" has been published in Physics Review Letters journal (Phys.Rev.Lett. 120 (2018) 211801) and also placed at arXiv
A new paper of the Collaboration
"Final results of the search for νμ→νe oscillations with the OPERA detector in the CNGS beam" has been submitted to a journal and placed in arXiv
A new paper of the Collaboration
"Study of charged hadron multiplicities in charged-current neutrino–lead interactions in the OPERA detector"
has been published in Eur.Phys.J. C78 (2018) no.1, 62
Scientists of the OPERA experiment report the discovery of tau neutrino appearance in the muon neutrino beam from CERN to Gran Sasso
The OPERA international experiment at the INFN Gran Sasso Laboratory (Italy) has detected the fifth occurrence of a tau neutrino. The neutrino started its flight at CERN as muon neutrino and, after travelling 730 km through the Earth, it arrived at Gran Sasso showing up as a tau neutrino.This important result was announced yesterday during a seminar held at the Gran Sasso Laboratory. According to the Spokesperson of the international research team, Giovanni De Lellis, from Federico II University and INFN in Naples, “The detection of a fifth tau neutrino is extremely important: the direct observation of the transition from muon to tau neutrinos has now achieved for the first time the 5 sigma statistical precision, the usual particle physics threshold for a discovery. We can thus definitely report the discovery of the appearance of tau neutrinos in a muon neutrino beam.” The detection of tau neutrinos from the oscillation of muon neutrinos was the motivation of the OPERA project, designed in the late nineties. “This task is extremely difficult due to two conflicting requirements: a huge, massive detector and a micrometric accuracy. The challenge is to bring to the thousands ton scale a detector based on the nuclear emulsion technology, a photographic technique unique in ensuring the required accuracy”, De Lellis says.
The international OPERA experiment, involving about 140 physicists from 26 research institutions in 11 countries, was designed to observe this phenomenon. First conceived as a speculation, neutrino oscillations have been a poorly known phenomenon for several decades. In 1998, it was demonstrated that muon neutrinos produced in cosmic-ray interactions arrive at the Earth fewer than expected. The result reported yesterday finally confirms that the “missing” neutrinos are indeed muon neutrinos oscillating into tau neutrinos. “The achievement reported yesterday was made possible thanks to the continuous effort of all the researchers involved in the project, to the excellent performance of the CERN neutrino beam and to the support of all the Funding Agencies”,
De Lellis finally says.
June 15, 2015
The seminar of Prof. "G. De Lellis - New results of the OPERA experiment" will start on Monday 15 Jun 2015 at 14:30 (Europe/Rome) at LNGS (Gran Sasso, Italy)
You can access the full event here:
March 25, 2014
Now the scientists of the OPERA experiment can claim the observation of the extremely rare neutrino oscillation in the tau channel. The OPERA international experiment at the INFN Gran Sasso Laboratory (Italy) has detected a fourth tau neutrino. The neutrino indeed started its flight at CERN as muon neutrino and, after travelling 730 km through the Earth, it arrived at the Gran Sasso laboratory transformed into a tau neutrino. This important result was announced today during a seminar held at the Gran Sasso Laboratory. According to the head of the international research team, Giovanni De Lellis, from Federico II University and INFN in Naples, “The detection of the fourth tau neutrino is a very important confirmation of the previously seen events. This transition is now seen for the first time
with a statistical significance exceeding the 4 sigma level: beyond the scientific jargon, this is equivalent to say that for the first time we have observed the extremely rare oscillation phenomenon of muon neutrinos to tau neutrinos, the aim of the OPERA project.” “If other tau neutrinos will be found in the data still to be analysed, an even higher significance level could be achieved. The important result reported today was made possible thanks to the dedication of all the researchers involved in the project”, De Lellis finally says.
The international OPERA experiment (involving 140 physicists from 28 research institutes in 11 countries) was designed to observe this exceptionally rare phenomenon. Neutrino oscillations have been a poorly known phenomenon for several decades. More than 15 years ago, it was demonstrated that muon neutrinos produced in cosmic-ray interactions arrive at the Earth fewer than expected. The result reported today explains why: the “missing” neutrinos are indeed those muon neutrinos oscillating into tau neutrinos.
13 August 2013 New paper "New results on $ν_μ\to ν_τ$ appearance with the OPERA experiment in the CNGS beam" is submitted to arXiv.
26 March 2013 A seminar at LNGS "New results from the OPERA experiment" by G.De Lellis will be broadcasted via http://streaming.lngs.infn.it/ at 14:30 of European time.
16 March 2013. New paper “Search for $ν_μ\rightarrow ν_e$ oscillations with the OPERA experiment in the CNGS beam” is submitted to JHEP and is available on arXive http://arxiv.org/abs/1303.3953
The new OPERA result sets new limits on the non-standard neutrino oscillation.
3 December 2012 After 5 years of operation the CNGS beam was stopped. In total it was 17.97 10**19 protons on target provided by the CNGS.
23 February 2012
The OPERA Collaboration, by continuing its campaign of verifications on the neutrino velocity measurement, has identified two issues that could significantly affect the reported result. The first one is linked to the oscillator used to produce the events time-stamps in between the GPS synchronizations. The second point is related to the connection of the optical fiber bringing the external GPS signal to the OPERA master clock.
These two issues can modify the neutrino time of flight in opposite directions. While continuing our investigations, in order to unambiguously quantify the effect on the observed result, the Collaboration is looking forward to performing a new measurement of the neutrino velocity as soon as a new bunched beam will be available in 2012. An extensive report on the above mentioned verifications and results will be shortly made available to the scientific committees and agencies.
23 September 2011
The paper "Measurement of the neutrino velocity with the OPERA detector in the CNGS beam" is available online in the arXiv repository (arXiv:1109.4897):
5 September 2011
The 2011 CNGS run started on March 18 and is well underway. The total number of pot accumulated so far is 3.96E19 corresponding to 23588 on-time events and 3947 candidate interactions in the target.
The CNGS average efficiency since the beginning of the run is 78.5%.
18 June 2010
The paper "Observation of a first \nu_\tau candidate in the OPERA experiment in the CNGS beam" has been published in Physics Letters B (N. Agafonova et al., Phys.Lett. B691 (2010) 138); it is available online in the arXiv repository (arXiv:1006.1623):
These results were presented by A. Ereditato in two special Seminars at the Gran Sasso laboratories (May 31) and at CERN (June 4).
The slide of the Seminar can be found here
The corresponding press release from the OPERA Collaboration can be found here
18 May 2010
On May 31, 2010, starting from 3:00 pm, A. Ereditato will give a seminar entitled "Observation of events with decay topologies in the OPERA experiment". The seminar will take place in the "E. Fermi" auditorium of LNGS. It will also be given at CERN on June 4.
The OPERA experiment at LNGS is searching in the CERN CNGS beam for the first detection of muon- to tau-neutrino oscillations in appearance mode. The Collaboration has analyzed a sub-sample of the statistics collected in the 2008-2009 runs. We shall disclose first analysis results based on the detection of decay topologies.
26 November 2009
The 2009 CNGS run is over. From June 1 to November 23 CNGS accumulated 3.52 10^19 protons-on-target. The OPERA detector observed 21428 events on time with the beam and about 3700 interactions in the target.
20 August 2009
The 2009 CNGS run started on Monday June 1 with the OPERA detector
From June 1 to August 17 the CNGS accumulated 1.54 10^19 protons-on-target.
By that time, OPERA has collected 9407 events on time with the beam and about 1600 candidate interactions in the target.
28 April 2009
L’Aquila earthquake of April 6th
On behalf of all its members, the OPERA Collaboration, which is rooted since 10 years in the community of L’Aquila, wishes to convey its deepest condolences to the families of the nearly 300 people who lost their lives in the dramatic earthquake of April the 6th. We express our heartful sympathy to all people that have lost their homes and are still suffering from the effects of this terrible event. We want to recognize with immense gratitude the care and commitment of our LNGS colleagues that – even in such difficult circumstances – have promptly restarted their activities to guarantee safety and full operation of all the experiments hosted in the Laboratories.
20-22 January 2009
OPERA MIZUNAMI Meeting
03 November 2008
The 2008 run is over. The CNGS beam delivered 1.78E19 protons on target. Corresponding to this statistics OPERA recorded about 10100 events correlated in time with the CNGS beam, among which 1700 candidates of neutrino interactions in the bricks.
13 October 2008
On Sunday 12th of October at 7pm, CNGS has integrated 1.23 10^19
protons on target. Opera has collected 6837 events on time with the beam
and 1151 candidate neutrino interactions in the bricks.
14 September 2008
The CNGS 2008 run started on June 18th. Up to Sunday 14/9 CNGS has integrated 0.738 10^19 protons on target. Opera has collected 4085 events on time with the beam and 652 candidate neutrino interactions in the bricks.