Jump to content

2011 OPERA faster-than-light neutrino anomaly

From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by 71.215.74.243 (talk) at 21:47, 11 April 2012 (rv with minor clarification: reverted version doesn't even state which error was larger, or which error was the actual cause of the unexpected result. Numeric values are completely appropriate for a summary). The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Fig. 1 Faster than light neutrinos. What OPERA apparently saw. Leftmost is the proton beam from the CERN SPS accelerator. It passes the beam current transformer (BCT), hits the target, creating first, pions and then, somewhere in the decay tunnel, neutrinos. The red lines are the Cern Neutrinos to Gran Sasso (CNGS) beam to the LNGS lab where the OPERA detector is. The proton beam is timed at the BCT. The left waveform is the measured distribution of protons, and the right that of the detected OPERA neutrinos. The shift is the neutrino travel time. Distance traveled is roughly 731 km. At the top are the GPS satellites providing a common clock to both sites, making time comparison possible. Only the PolaRx GPS receiver is above-ground, and fiber cables bring the time underground.
Fig. 1 What OPERA saw. Leftmost is the proton beam from the CERN SPS accelerator. It passes the beam current transformer (BCT), hits the target, creating first, pions and then, somewhere in the decay tunnel, neutrinos. The red lines are the Cern Neutrinos to Gran Sasso (CNGS) beam to the LNGS lab where the OPERA detector is. The proton beam is timed at the BCT. The left waveform is the measured distribution of protons, and the right that of the detected OPERA neutrinos. The shift is the neutrino travel time. Distance traveled is roughly 731 km. At the top are the GPS satellites providing a common clock to both sites, making time comparison possible. Only the PolaRx GPS receiver is above-ground, and fiber cables bring the time underground.

The faster-than-light neutrino anomaly was the mistaken reporting by the OPERA experiment of subatomic particles, neutrinos, appearing to travel faster than light. It was considered anomalous since speeds higher than that of light in a vacuum are generally thought to violate special relativity, a cornerstone of the modern understanding of physics for over a century.[1][2]

This result was publicly announced in September 2011 with the stated intent of promoting further inquiry and debate. The false measurement suggesting faster-than-light neutrinos was later explained as due to one of two previously undetected errors: An incompletely screwed in fiber optic cable fastener connection subtracted about 70 nanoseconds from the measured time of flight.[3] The other error, caused by a clock oscillator ticking too fast, added a much smaller amount to the time of flight measurement, resulting in the neutrinos apparently arriving about 57 nanoseconds too soon.[4] The errors were first confirmed by OPERA after a ScienceInsider report on two possible sources of errors that could significantly affect the reported result.[5] OPERA spokesperson Antonio Ereditato and physics coordinator Dario Autiero resigned on March 30, 2012.[6]

In March 2012, the colocated ICARUS experiment reported neutrino velocities consistent with the speed of light in the same short-pulse beam OPERA had measured in November 2011. ICARUS used a partly different timing system from OPERA and measured seven different neutrinos. The Gran Sasso experiments BOREXINO, ICARUS, LVD and OPERA will all measure neutrino velocity with a short-pulsed beam in May to obtain a neutrino-velocity number with high accuracy.[7][8]

Detection

The experiment created a form of neutrinos, muon neutrinos, at CERN's older SPS accelerator, on the Franco–Swiss border, and detected them at the LNGS lab in Gran Sasso, Italy. OPERA researchers used common-view GPS, derived from standard GPS, to measure the times and place coordinates at which the neutrinos were created and detected. As computed, the neutrinos' average time of flight turned out to be less than what light would need to travel the same distance in a vacuum. In a two-week span up to November 6, the OPERA team repeated the measurement with a different way of generating neutrinos, which helped measure travel time of each detected neutrino separately. This eliminated some possible errors related to matching detected neutrinos to their creation time.[9] The OPERA collaboration stated in their initial press release that further scrutiny and independent tests were necessary to definitely confirm or refute the results.[7]

First results

In a March 2011 analysis of their data, scientists of the OPERA collaboration reported evidence that neutrinos they produced at CERN in Geneva and recorded at the OPERA detector at Gran Sasso, Italy, had traveled faster than light. The neutrinos were calculated to have arrived approximately 60.7 nanoseconds (60.7 billionths of a second) sooner than light would have if traversing the same distance in a vacuum. After six months of cross checking, on September 23, 2011, the researchers announced that neutrinos had been observed traveling at faster-than-light speed.[10] Similar results were obtained using higher-energy (28 GeV) neutrinos, which were observed to check if neutrinos' velocity depended on their energy. The particles were measured arriving at the detector faster than light by approximately one part per 40,000, with a 0.2-in-a-million chance of being wrong, if the error were distributed as a bell curve (significance of six sigma). This measure included estimates for both errors in measuring and errors from the statistical procedure used. It was, however, a measure of precision, not accuracy, which could be influenced by elements such as incorrect computations or wrong readouts of instruments.[11][12] For particle physics experiments involving collision data, the standard for a discovery announcement is a five-sigma error limit, looser than the observed six-sigma limit.[13]

The preprint of the research stated "[the observed] deviation of the neutrino velocity from c [speed of light in vacuum] would be a striking result pointing to new physics in the neutrino sector" and referred to the "early arrival time of CNGS muon neutrinos" as an "anomaly".[14] OPERA spokesperson Antonio Ereditato explained that the OPERA team had "not found any instrumental effect that could explain the result of the measurement".[7] James Gillies, a spokesperson for CERN, said on September 22 that the scientists were "inviting the broader physics community to look at what they [had] done and really scrutinize it in great detail, and ideally for someone elsewhere in the world to repeat the measurements".[15]

Internal replication

Fig. 2 Analysis of the internal replication. Distribution of the early-arrival values for each detected neutrino with bunched-beam rerun. The mean value is indicated by the red line and the blue band.
Fig. 2 Analysis of the internal replication in November. Distribution of the early-arrival values for each detected neutrino with bunched-beam rerun. The mean value is indicated by the red line and the blue band.

In November, OPERA published refined results where they noted their chances of being wrong as even less, thus tightening their error bounds. Neutrinos arrived approximately 57.8 ns earlier than if they had traveled at light-speed, giving a relative speed difference of approximately one part per 42,000 against that of light. The new significance level became 6.2 sigma.[16] The collaboration submitted its results for peer-reviewed publication to the Journal of High Energy Physics.[17][18]

In the same paper, the OPERA collaboration also published the results of a repeat experiment running from October 21, 2011 to November 7, 2011. They detected twenty neutrinos consistently indicating an early neutrino arrival of approximately 62.1 ns, in agreement with the result of the main analysis.[19]

Measurement errors

In February 2012, the OPERA collaboration announced two possible sources of error that could have significantly influenced the results.[7]

  • A link from a GPS receiver to the OPERA master clock was loose, which increased the delay through the fiber and wrongly enhanced the faster-than-light effect.[20].[21]
  • A clock on an electronic board ticked faster than its expected 10 MHz frequency, lengthening the reported flight-time of neutrinos and wrongly weakening the apparent faster-than-light effect. OPERA stated the component had been operating outside its specifications.[22]

In March 2012 an LNGS seminar was held, confirming the fiber cable was not fully screwed in during data gathering.[4] LVD researchers compared the timing data for cosmic muon neutrinos hitting both the OPERA and the nearby LVD detector between 2007-2008 and 2008-2011. The shift obtained for the 2008-2011 period agreed with the OPERA anomaly. The researchers also found photographs showing the cable had been loose by October 13, 2011.

Independent Replication

Main article: Measurements of neutrino speed

Replication by a separate lab was thought to be the key test of the result.[23]

ICARUS

In March 2012, the colocated ICARUS experiment refuted the OPERA results by measuring neutrino velocity to be that of light. ICARUS measured speed for seven neutrinos in the same short-pulse beam OPERA had checked in November 2011, and found them, on average, traveling at the speed of light. The results were from a trial run of neutrino-velocity measurements slated for May. Ereditato confirmed the results were in accord with the possible errors discovered by OPERA.[24] Autiero, however, alluded to the reproduction of OPERA's results using the same beam in October and November (see "internal replication" above), and stated the researchers continued to search for possible errors in the experiment. Others such as theoretical physicist Adam Falkowski said that this conclusively closed the OPERA case.[25]

Other experiments

After the initial results, OPERA and CERN advanced two requests: to Fermilab, a US lab which has both a neutrino generator and a detector; and to the T2K experiment, a neutrino generator and detector in Japan. Although both initially agreed to test the OPERA result,[26] T2K is now unsure of its commitment.[27]

Five efforts are currently underway to measure neutrino velocity.[28] Of these, Fermilab has stated that the detectors for the MINOS project are being upgraded,[29] and new results are not expected until at least 2012. A result based on data collected over the last five years is expected to be available sometime toward the end of 2012. Fermilab scientists hope to closely analyze and place bounds on the errors in their timing system to achieve a precision of 15 nanoseconds, enough to confirm or refute the OPERA result.[30] The lab's director Pier Oddone states MINOS may make some measurements before March 2012, when the proton beam making the neutrinos is scheduled to be shut down for a year. More thorough measurements will be made in 2013 and a full analysis done in 2014.[31] New sensitive equipment has been installed and data will be collected with it in April 2012, and analyzed by the end of the year.[28] The cost is expected to be roughly half-a-million dollars.[32]

The Borexino and ICARUS experiments (both located at Gran Sasso) will begin checks of OPERA's results in 2012.[33] OPERA itself had planned to cross check clock synchronization between CERN and LNGS, perhaps by using an optical fiber. The researchers will also continue to take data into 2012, expecting to detect and time around a hundred neutrinos more in a couple of months, to improve the accuracy of the results.[34] The CNGS beam, now shut down, will restart mid-March 2012.[35] OPERA, in addition to detecting neutrino interactions at the scintillation counters,[36] is gearing up to time neutrino interactions with its next-in-detection-stage resistive plate chamber (RPC) detectors as well.[35][37] They are also improving their time resolution, reducing a jitter more prominently seen with the bunched beam. They also planned to redo all measurements of both delays and the geodesy distance. The experiment will be repeated with both bunched and standard beams, and with both neutrinos and antineutrinos on the bunched beam.[38] In parallel, CERN scientists will use diamond radiation-detectors to measure muons, an intermediate particle produced along with the neutrinos, after the point where neutrinos are produced.[35]

The measurement

The OPERA experiment was designed to capture how neutrinos switch between different identities, but Autiero realized the equipment could be used to precisely measure neutrino speed too.[39] A tentative result from the MINOS experiment at Fermilab showing neutrinos traveling faster than light lent credence to the idea.[40] The principle of the OPERA neutrino velocity experiment was to compare travel time of neutrinos against travel time of light. The neutrinos in the experiment emerged at CERN and flew to the OPERA detector. The researchers divided this distance by the speed of light in vacuum to predict what the neutrino travel time should be. They compared this expected value to the measured commute time.[41]

Overview

The OPERA team used an already existing beam of neutrinos traveling continuously from CERN to LNGS, the CERN Neutrinos to Gran Sasso beam, for the measurement. Measuring speed meant measuring the distance traveled by the neutrinos from their source to where they were detected, and the time taken by them to travel this length. The source at CERN was more than 730 kilometres (450 mi) away from the detector at LNGS (Gran Sasso). The experiment was tricky because there was no way to time an individual neutrino, necessitating more complex steps. As shown in Fig. 1, CERN generates neutrinos by slamming protons, in pulses of length 10.5 microseconds (10.5 millionths of a second), into a graphite target to produce intermediate particles, which decay into neutrinos. OPERA researchers measured the protons as they passed a section called the beam current transducer (BCT) and took the transducer's position as the neutrinos' starting point. The protons did not actually create neutrinos for another kilometer, but because both protons and the intermediate particles moved almost at light speed, the error from the assumption was acceptably low.

The clocks at CERN and LNGS had to be in sync, and for this the researchers used high-quality GPS receivers, backed up with atomic clocks, at both places. This system timestamped both the proton pulse and the detected neutrinos to a claimed accuracy of 2.3 nanoseconds. But the timestamp could not be read like a clock. At CERN, the GPS signal came only to a receiver at a central control room, and had to be routed with cables and electronics to the computer in the neutrino-beam control room which recorded the proton pulse measurement (Fig. 3). The delay of this equipment was 10,085 nanoseconds and this value had to be added to the time stamp. The data from the transducer arrived at the computer with a 580 nanoseconds delay, and this value had to be subtracted from the time stamp. To get all the corrections right, physicists had to measure exact lengths of the cables and the latencies of the electronic devices. On the detector side, neutrinos were detected by the charge they induced, not by the light they generated, and this involved cables and electronics as part of the timing chain. Fig. 4 shows the corrections applied on the OPERA detector side.

Since neutrinos could not be accurately tracked to the specific protons producing them, an averaging method had to be used. The researchers added up the measured proton pulses to get an average distribution in time of the individual protons in a pulse. The time at which neutrinos were detected at Gran Sasso was plotted to produce another distribution. The two distributions were expected to have similar shapes, but be separated by 2.4 milliseconds (2.4 thousandths of a second), the time it takes to travel the distance at light speed. The experimenters used an algorithm, maximum likelihood, to search for the time shift that best made the two distributions to coincide. The shift so calculated, the statistically measured neutrino arrival time, was approximately 60 nanoseconds shorter than the 2.4 milliseconds neutrinos would have taken if they traveled just at light speed. In a later experiment, the proton pulse width was shortened to 3 nanoseconds, and this helped the scientists to narrow the generation time of each detected neutrino to that range.[42]

Measuring distance

Distance was measured by accurately fixing the source and detector points on a global coordinate system (ETRF2000). CERN surveyors used GPS to measure the source location. On the detector side, the OPERA team worked with a geodesy group from the Sapienza University of Rome to locate the detector's center with GPS and standard map-making techniques. To link the surface GPS location to the coordinates of the underground detector, traffic had to be partially stopped on the access road to the lab. Combining the two location measurements, the researchers calculated the distance,[43] to an accuracy of 20 cm within the 730 km path.[44]

Measuring trip time

The travel time of the neutrinos had to be measured by tracking the time they were created, and the time they were detected, and using a common clock to ensure the times were in sync. As Fig. 1 shows, the time measuring system included the neutrino source at CERN, the detector at LNGS (Gran Sasso), and a satellite element common to both. The common clock was the time signal from multiple GPS satellites visible from both CERN and LNGS. CERN's beams-department engineers worked with the OPERA team to provide a travel time measurement between the source at CERN and a point just before the OPERA detector's electronics, using accurate GPS receivers. This included timing the proton beams' interactions at CERN, and timing the creation of intermediate particles eventually decaying into neutrinos (see Fig. 3).

Fig. 3 CERN SPS/CNGS time measuring system. Protons circulate in the SPS till kicked by a signal to the beam current transformer (BCT) and on to the target. The BCT is the origin for the measurement. Both the kicker signal and the proton flux in the BCT get to the waveform digitizer (WFD), the first through the Control Timing Receiver (CTRI). The WFD records the proton distribution. The common CNGS/LNGS clock comes from GPS via the PolaRx receiver and the central CTRI, where the CERN UTC and General Machine Timing (GMT) also arrive. The difference between the two references is recorded. The marker x ± y indicates an 'x' nanosecond delay with a 'y' ns error bound.
Fig. 3 CERN SPS/CNGS time measuring system. Protons circulate in the SPS till kicked by a signal to the beam current transformer (BCT) and on to the target. The BCT is the origin for the measurement. Both the kicker signal and the proton flux in the BCT get to the waveform digitizer (WFD), the first through the Control Timing Receiver (CTRI). The WFD records the proton distribution. The common CNGS/LNGS clock comes from GPS via the PolaRx receiver and the central CTRI, where the CERN UTC and General Machine Timing (GMT) also arrive. The difference between the two references is recorded. The marker x ± y indicates an 'x' nanosecond delay with a 'y' ns error bound.
Fig. 4 OPERA time measuring system at LNGS: various delays of the timing chain, and the standard deviations of the error. The top half of the picture is the common GPS clock system (PolaRx2e is the GPS receiver), and the bottom half is the underground detector. Fiber cables bring the GPS clock underneath. The underground detector consists of the blocks from the tt-strip to the FPGA. Errors for each component are shown as x ± y, where x is the delay caused by the component in transmitting time information, and y is the expected bound on that delay.
Fig. 4 OPERA time measuring system at LNGS: various delays of the timing chain, and the standard deviations of the error. The top half of the picture is the common GPS clock system (PolaRx2e is the GPS receiver), and the bottom half is the underground detector. Fiber cables bring the GPS clock underneath. The underground detector consists of the blocks from the tt-strip to the FPGA. Errors for each component are shown as x ± y, where x is the delay caused by the component in transmitting time information, and y is the expected bound on that delay.
Timing systems at the two ends of the OPERA experiment

Researchers from OPERA measured the remaining delays and calibrations not included in the CERN calculation: those shown in Fig. 4. The neutrinos were detected in an underground lab, but the common clock from the GPS satellites was visible only above ground level. The clock value noted above-ground had to be transmitted to the underground detector with an 8 km fiber cable. The delays associated with this transfer of time had to be accounted for in the calculation. How much the error could vary (the standard deviation of the errors) mattered to the analysis, and had to be calculated for each part of the timing chain separately. Special techniques were used to measure the length of the fiber and its consequent delay, required as part of the overall calculation.[43]

In addition, to sharpen resolution from the standard GPS 100 nanoseconds to the 1 nanosecond range metrology labs achieve, OPERA researchers used Septentrio’s precise PolaRx2eTR GPS timing receiver,[45] along with consistency checks across clocks (time calibration procedures) which allowed for common-view time transfer. The PolaRx2eTR allowed measurement of the time offset between an atomic clock and each of the Global Navigation Satellite System satellite clocks. For calibration, the equipment was taken to the Swiss Metrology Institute (METAS).[43] In addition, highly stable cesium clocks were installed both at LNGS and CERN to cross-check GPS timing and to increase its precision. After OPERA found the superluminal result, the time calibration was rechecked both by a CERN engineer and the German Institute of Metrology (PTB).[43] Time-of-flight was eventually measured to an accuracy of 10 nanoseconds.[7][46] The final error bound was derived by combining the variance of the error for the individual parts.

The analysis

The OPERA team analyzed the results in different ways and using different experimental methods. Following the initial main analysis released in September, three further analyses were made public in November. In the main November analysis, all the existing data were reanalyzed to allow adjustments for other factors, such as the Sagnac effect in which the Earth's rotation affects the distance traveled by the neutrinos. Then an alternative analysis adopted a different model for the matching of the neutrinos to their creation time. The third analysis of November focused on a different experimental setup ('the rerun') which changed the way the neutrinos were created.

In the initial setup, every detected neutrino would have been produced sometime in a 10,500 nanoseconds (10.5 microseconds) range, since this was the duration of the proton beam spill generating the neutrinos. It was not possible to isolate neutrino production time further within the spill. Therefore, in their main statistical analyses, the OPERA group generated a model of the proton waveforms at CERN, took the various waveforms together, and plotted the chance of neutrinos being emitted at various times (the global probability density function of the neutrino emission times). They then compared this plot against a plot of the arrival times of the 15,223 detected neutrinos. This comparison indicated neutrinos had arrived at the detector 57.8 nanoseconds faster than if they had been traveling at the speed of light in vacuum. An alternative analysis in which each detected neutrino was checked against the waveform of its associated proton spill (instead of against the global probability density function) led to a compatible result of approximately 54.5 nanoseconds.[47]

The November main analysis, which showed an early arrival time of 57.8 nanoseconds, was conducted blind to avoid observer bias, whereby those running the analysis might inadvertently fine-tune the result toward expected values. To this end, old and incomplete values for distances and delays from the year 2006 were initially adopted. With the final correction needed not yet known, the intermediate expected result was also an unknown. Analysis of the measurement data under those 'blind' conditions gave an early neutrino arrival of 1043.4 nanoseconds. Afterward, the data were analyzed again taking into consideration the complete and actual sources of errors. If neutrino and light speed were the same, a subtraction value of 1043.4 nanoseconds should have been obtained for the correction. However, the actual subtraction value amounted to only 985.6 nanoseconds, corresponding to an arrival time 57.8 nanoseconds earlier than expected.[48]

Two facets of the result came under particular scrutiny within the neutrino community: the GPS synchronization system, and the profile of the proton beam spill that generated neutrinos.[49] The second concern was addressed in the November rerun: for this analysis, OPERA scientists repeated the measurement over the same baseline using a new CERN proton beam which circumvented the need to make any assumptions about the details of neutrino production during the beam activation, such as energy distribution or production rate. This beam provided proton pulses of 3 nanoseconds each with up to 524 nanosecond gaps. This meant a detected neutrino could be tracked uniquely to its generating 3 nanoseconds pulse, and hence its start and end travel times could be directly noted. Thus, the neutrino's speed could now be calculated without having to resort to statistical inference.[7]

In addition to the four analyses mentioned earlier—September main analysis, November main analysis, alternative analysis, and the rerun analysis—the OPERA team also split the data by neutrino energy and reported the results for each set of the September and November main analyses. The rerun analysis had too few neutrinos to consider splitting the set further.

Reception by the physics community

After the initial report of apparent superluminal velocities of neutrinos, Nobel laureates Steven Weinberg,[50] George Smoot III, and Carlo Rubbia,[51] and other physicists not affiliated with the experiment, including Michio Kaku,[52] expressed skepticism about the accuracy of the experiment on the basis that the results challenged a long-held theory consistent with the results of many other tests of special relativity. [53] Nevertheless, Ereditato, the OPERA spokesperson, stated that no one had an explanation that invalidated the experiment's results.[54]

Previous experiments of neutrino speed played a role in the reception of the OPERA result by the physics community. Those experiments did not detect statistically significant deviations of neutrino speeds from the speed of light. For instance, Astronomer Royal Martin Rees and theoretical physicists Lawrence Krauss[55] and Stephen Hawking[56] stated neutrinos from the SN 1987A supernova explosion arrived almost at the same time as light, indicating no faster-than-light neutrino speed. John Ellis, theoretical physicist at CERN, believed it difficult to reconcile the OPERA results with the SN 1987A observations.[57] Observations of this supernova restricted 10 MeV anti-neutrino speed to less than 20 parts per billion (ppb) over lightspeed. This was one of the reasons most physicists suspected the OPERA team had made an error.[58]

Physicists affiliated with the experiment had refrained from interpreting the result, stating in their paper:

Despite the large significance of the measurement reported here and the stability of the analysis, the potentially great impact of the result motivates the continuation of our studies in order to investigate possible still unknown systematic effects that could explain the observed anomaly. We deliberately do not attempt any theoretical or phenomenological interpretation of the results.[59]

Andrew Cohen and Glashow have predicted that superluminal neutrinos would radiate electrons and positrons and lose energy through vacuum Cherenkov effects, where a particle traveling faster than light decays continuously into other slower particles.[60] However, this energy attrition was absent both in the OPERA experiment and in the colocated ICARUS experiment, which uses the same CNGS beam as OPERA.[1] This discrepancy was seen by Cohen and Glashow to present "a significant challenge to the superluminal interpretation of the OPERA data".[60]

Many other scientific papers on the anomaly were published as arXiv preprints or in peer reviewed journals. Some of them criticized the result, while others tried to find theoretical explanations, replacing or extending special relativity and the standard model.[61]

Discussions within the OPERA collaboration

Ereditato, the person representing the OPERA collaboration, specifically asked team members individually whether they wanted to sign the paper describing the results, deviating from the default opt-in system.[38] Around 15 of the almost 195 researchers did not sign on to the first preprint of the paper, since they thought the publication was premature and further experimental checks were required.[62] The experiment's advisory board, however, felt it their duty to open the results to public scrutiny.[39] Some of the original dissenters signed the final paper, whereas at least one person who had signed the first paper did not sign the final one.[63]

The final dissenters in the collaboration were concerned the time window for neutrino detection, the spread of the histograms in Fig. 2, was initially assumed to be 10 ns but revealed by Autiero to be 50 ns after the tests were done. While the discrepancy did not affect the test results, the dissenters considered this poor experimental procedure. They were also unhappy that only a small fraction of the analysis, carried out by Autiero, had been independently checked by others, leaving open the possibility of errors in the analysis.[17] OPERA team member Luca Stanco of the National Institute of Nuclear Physics (INFN) in Italy considered the OPERA results an embarrassment. He believed that was the consensus of the physics community since the results fit no known physics framework, and they urgently needed to be independently confirmed.[64]

The fiber delay had last been measured by Autiero in 2008. Some researchers had suggested remeasuring the delay before the JHEP submission in November, but the OPERA scientific management had not agreed.[20]

Ereditato and Autiero resigned their leadership positions on March 30, 2012. The resignations followed a vote of no confidence among the more than thirty group team leaders.[6][65]

See also

Notes

  1. ^ a b Reich (2011b)
  2. ^ Many sources describe faster-than-light (FTL) as violating special relativity (SR): (Reich 2011c; Cho 2011a; Choi 2011). Other reliable sources disagree, though; for FTL not necessarily violating SR, see ("Tachyon" 2011).
  3. ^ Strassler, M. (2012) "OPERA: What Went Wrong" profmattstrassler.com
  4. ^ a b Reich (2012c)
  5. ^ (Cartlidge 2012; Cartlidge 2012b)
  6. ^ a b Edwin Cartligde (March 30, 2012). "Leaders of Faster-Than-Light Experiment Step Down". ScienceInsider.
  7. ^ a b c d e f ("OPERA experiment reports anomaly in flight time of neutrinos from CERN to Gran Sasso" 2011)
  8. ^ ICARUS (2012)
  9. ^ Cartlidge (2011b)
  10. ^ Reich (2011a)
  11. ^ Brunetti (2011)
  12. ^ (The OPERA collaboration 2011)
  13. ^ Seife (2000)
  14. ^ (The OPERA collaboration 2011, p. 29)
  15. ^ Jordans & Borenstein (2011a)
  16. ^ version 2 of (The OPERA collaboration 2011)
  17. ^ a b c Cartlidge 2011c
  18. ^ Jha 2011
  19. ^ ("A new proton spill from CERN to Gran Sasso" 2011); version 2 of (The OPERA collaboration 2011)
  20. ^ a b Cartlidge (2012c)
  21. ^ Lindinger & Hagner (2012)
  22. ^ ("Science in action" 2012)
  23. ^ Reich (2011c)
  24. ^ Jordans (2012)
  25. ^ (Brumfiel 2012)
  26. ^ (Brown & Khan 2011)
  27. ^ ("T2K statement on the OPERA anomaly" 2011)
  28. ^ a b (Boyle 2012)
  29. ^ (Hooker 2011)
  30. ^ (Pease 2011)
  31. ^ Shiga (2011)
  32. ^ Reich (2012b)
  33. ^ (Rincon 2011)
  34. ^ (Pease 2011)
  35. ^ a b c Palladino, Migliozzi & Kahle (2011)
  36. ^ (The OPERA collaboration 2011)
  37. ^ Grossman (2011b)
  38. ^ a b c Ramachandran (2012)
  39. ^ a b Nosengo (2011)
  40. ^ Cartlidge (2011a)
  41. ^ Cho (2011b)
  42. ^ The CERN-neutrino-to-Gran-Sasso beam citation is from ("Upstream from OPERA: extreme attention to detail" 2011); the rest of the description draws heavily on the article by Cho (2011b), and, to some extent, by Cartlidge (2011b).
  43. ^ a b c d Upstream from OPERA: extreme attention to detail (2011)
  44. ^ (Colosimo et al. 2011)
  45. ^ ("Knocking Einstein: Septentrio in CERN experiment" 2011)
  46. ^ Feldmann 2011; Komatsu 2011
  47. ^ (The OPERA collaboration 2011, pp. 14, 16–21)
  48. ^ version 2 of (The OPERA collaboration 2011)
  49. ^ Reich (2011a)
  50. ^ Matson (2011)
  51. ^ ("U.S. scientists to test findings" 2011)
  52. ^ Jordans & Borenstein (2011b)
  53. ^ Reich (2011c); Cho 2011b; Overbye 2011; Gary 2011
  54. ^ Palmer (2011)
  55. ^ Matson (2011)
  56. ^ "Hawking on the future of mankind" (2012)
  57. ^ Brumfiel (2011)
  58. ^ Cho (2011b)
  59. ^ (The OPERA collaboration 2011, p. 29)
  60. ^ a b Cohen & Glashow (2011)
  61. ^ Resource list at INFN SuperLuminal Neutrino
  62. ^ (Cartlidge 2011b; Grossman 2011a; "More data shows neutrinos still faster than light" 2011; Grossman 2011b)
  63. ^ [17][38]Grossman 2011b
  64. ^ Grossman (2012)
  65. ^ DicoveryNews article

References

Boyle, Alan (February 18, 2012), Answers ahead for physics' puzzles, MSNBC, retrieved February 18, 2012

Brown, E.; Khan, A. (September 23, 2011), "Faster than light? CERN findings bewilder scientists", Los Angeles Times, retrieved September 24, 2011, MINOS scientists may perform experiments of their own in as soon as six months, said particle physicist and MINOS co-spokesperson Jenny Thomas. Plans to test the CERN results in Japan's multinational T2K (Tokai-to-Kamioka) experiment are in the works, said neutrino physicist and T2K spokesman Chang Kee Jung

Brumfiel, G. (September 23, 2011), "Particles break light-speed limit", Nature News, doi:10.1038/news.2011.554, retrieved October 22, 2011

Brumfiel, G. (March 16, 2012), "Neutrinos not faster than light", Nature News, doi:10.1038/nature.2012.10249, retrieved March 16, 2012

Brunetti, G. (2011), Neutrino velocity measurement with the OPERA experiment in the CNGS beam (Doctoral dissertation) (PDF), retrieved October 8, 2011

Cartlidge, E. (October 7, 2011), "Tension emerges within OPERA collaboration", Physicsworld.com{{citation}}: CS1 maint: date and year (link)

Cartlidge, E. (October 21, 2011), "Faster-than-light result to be scrutinized", ScienceInsider, American Association for the Advancement of Science, retrieved October 21, 2011{{citation}}: CS1 maint: date and year (link)

Cartlidge, E. (November 17, 2011), "Faster-Than-Light neutrinos: OPERA confirms and submits results, but unease remains", ScienceInsider, American Association for the Advancement of Science, retrieved November 17, 2011{{citation}}: CS1 maint: date and year (link)

Cartlidge, E. (February 22, 2012), "Breaking news: Error undoes faster-than-light neutrino results", ScienceInsider, American Association for the Advancement of Science, retrieved February 22, 2012

Cartlidge, E. (February 24, 2012), "Official Word on Superluminal Neutrinos Leaves Warp-Drive Fans a Shred of Hope—Barely", ScienceInsider, American Association for the Advancement of Science, retrieved February 24, 2012{{citation}}: CS1 maint: date and year (link)

Cartlidge, E. (March 1, 2012), "Loose cable may unravel faster-than-light result", Science, 335 (6072): 1027, doi:10.1126/science.335.6072.1027 {{citation}}: |access-date= requires |url= (help)CS1 maint: date and year (link)

Cho, A. (September 30, 2011), "From Geneva to Italy faster than a speeding photon?", Science, 333 (6051): 1809, Bibcode:2011Sci...333.1809C, doi:10.1126/science.333.6051.1809, retrieved November 21, 2011{{citation}}: CS1 maint: date and year (link)

Cho, A. (December 2, 2011), "Where does the time go?", Science, 334 (6060): 1200–1201, Bibcode:2011Sci...334.1200C, doi:10.1126/science.334.6060.1200{{citation}}: CS1 maint: date and year (link)

Choi, C. Q. (October 13, 2011), "Leading light: What would faster-than-light neutrinos mean for physics", Scientific American

Colosimo, G.; Crespi, M.; Mazzoni, A.; Riguzzi, F.; Jones, M.; Missiaen, D. (October 10, 2011), Determination of the CNGS global geodesy, OPERA http://operaweb.lngs.infn.it/Opera/publicnotes/note132.pdf {{citation}}: Missing or empty |title= (help)

Feldmann, T. (September 2011), Relative calibration of the GPS time link between CERN and LNGS (PDF), Physikalisch-Technische Bundesanstalt (German National Metrological Institute){{citation}}: CS1 maint: date and year (link)

Gary, S. (November 25, 2011), "Neutrinos win but Einstein hasn't lost yet", ABC Science, retrieved December 3, 2011

Grossman, L. (October 25, 2011), "Faster-than-light neutrino result to get extra checks", New Scientist, retrieved October 25, 2011{{citation}}: CS1 maint: date and year (link)

Grossman, L. (November 18, 2011), "New results show neutrinos still faster than light", New Scientist, retrieved November 18, 2011{{citation}}: CS1 maint: date and year (link)

Grossman, L. (January 4, 2012), "Faster-than-light neutrinos dealt another blow", New Scientist, retrieved January 4, 2012

Hawking on the future of mankind, BBC, January 6, 2012, retrieved January 6, 2012

Hooker, B. (2011), "OPERA experiment reports anomaly in flight time of neutrinos", Fermilab Today, Batavia, Illinois: Fermilab, retrieved September 24, 2011

ICARUS collaboration (March 15, 2012), Measurement of the neutrino velocity with the ICARUS detector at the CNGS beam, arXiv:1203.3433 {{citation}}: |access-date= requires |url= (help)

Jha, A. (November 17, 2011), "Neutrinos still faster than light in latest version of experiment", The Guardian, retrieved November 17, 2011

Jordans, F. (March 16, 2012), "New test nixes findings about faster-than-light neutrinos", MSNBC, Associated Press, retrieved March 16, 2012

Jordans, F.; Borenstein, S. (September 22, 2011), "Roll over Einstein: Law of physics challenged (update 3)", PhysOrg, Associated Press, retrieved September 24, 2011{{citation}}: CS1 maint: date and year (link)

Jordans, F.; Borenstein, S. (24 September 2011), Challenging Einstein is usually a losing venture, AP/Yahoo News, retrieved September 26, 2011{{citation}}: CS1 maint: date and year (link)

Knocking Einstein: Septentrio in CERN experiment on faster-than-Light neutrinos, GPS World, September 28, 2011, retrieved November 20, 2011

Komatsu, M. (October 4, 2011), Seminar: Measurement of the neutrino velocity with the OPERA detector in the CNGS beam (PDF), Institute of Particle and Nuclear Studies(IPNS), High Energy Accelerator Research Organization (KEK), retrieved November 20, 2011

Lindinger, Manfred; Hagner, Caren (February 24, 2012), "Interview über die möglichen Fehlerquellen: Messfehler könnten Überlichtgeschwindigkeit erklären", Frankfurter Allgemeine Zeitung, retrieved February 24, 2012. See also this translation into English (see first comment): Measurement errors could explain FTL.

Matson, J. (September 26, 2011), "Faster-than-light neutrinos? Physics luminaries voice doubts", Scientific American, retrieved October 9, 2011

"More data shows neutrinos still faster than light", New Scientist, 212 (2840): 17, November 26, 2011, 2005, doi:10.1016/S0262-4079(11)62883-2 {{citation}}: |access-date= requires |url= (help); Check date values in: |date= (help)

"A new proton spill from CERN to Gran Sasso", CERN Bulletin, CERN, November 7, 2011, retrieved November 12, 2011

Noorden, R. V. (December 21, 2011), "365 days: 2011 in review", Nature News, Bibcode:2011Natur.480..426V, doi:10.1038/480426a {{citation}}: |access-date= requires |url= (help)

Nosengo, N. (December 21, 2011), "Dario Autiero: Relativity challenger", Nature News, Bibcode:2011Natur.480..437B, doi:10.1038/480437a {{citation}}: |access-date= requires |url= (help)

The OPERA collaboration (September 22, 2011), Measurement of the neutrino velocity with the OPERA detector in the CNGS beam, arXiv:1109.4897, Bibcode:2011arXiv1109.4897T

OPERA experiment reports anomaly in flight time of neutrinos from CERN to Gran Sasso, CERN, September 23, 2011, retrieved February 23, 2011. Also includes press releases from November 18, 2011, February 23, 2012, and March 16, 2012. "OPERA's measurement: theory's speaking time", CERN Bulletin, October 24, 2011, retrieved October 28, 2011

Overbye, D. (November 18, 2011), "Scientists report second sighting of faster-than-light neutrinos", New York Times, retrieved November 18, 2011

Palladino, V.; Migliozzi, P.; Kahle, K. (October–December 2011), "A word about faster-than-light neutrinos", EuCARD( European Coordination for Accelerator Research and Development) Newsletter (11), retrieved December 19, 2011{{citation}}: CS1 maint: date and year (link) CS1 maint: date format (link)

Palmer, J. (November 18, 2011), Neutrino experiment repeat at CERN finds same result, BBC, retrieved November 20, 2011

Pease, R. (November 21, 2011), Discovery: Neutrinos, BBC, retrieved November 21, 2011

Ramachandran, R (March 10–23, 2012), "Faster than light?", Frontline, 29 (5), retrieved March 11, 2012{{citation}}: CS1 maint: date and year (link) CS1 maint: date format (link)

Reich, E. S. (September 27, 2011), "Speedy neutrinos challenge physicists", Nature News, 477 (520), Bibcode:2011Natur.477..520R, doi:10.1038/477520a {{citation}}: |access-date= requires |url= (help)CS1 maint: date and year (link)

Reich, E. S. (October 20, 2011), "Finding puts brakes on faster-than-light neutrinos", Nature News, doi:10.1038/news.2011.605{{citation}}: CS1 maint: date and year (link)

Reich, E. S. (November 18, 2011), "Neutrino experiment replicates faster-than-light finding", Nature News, doi:10.1038/nature.2011.9393 {{citation}}: |access-date= requires |url= (help)CS1 maint: date and year (link)

Reich, E. S. (February 22, 2012), "Flaws found in faster-than-light neutrino measurement", Nature News, doi:10.1038/nature.2012.10099 {{citation}}: |access-date= requires |url= (help)

Reich, E. S. (February 27, 2012), "Timing glitches dog neutrino claim", Nature News, Bibcode:2012Natur.483...17S, doi:10.1038/483017a {{citation}}: |access-date= requires |url= (help)CS1 maint: date and year (link)

Reich, E. S. (April 2, 2012), "Embattled neutrino project leaders step down", Nature News, doi:10.1038/nature.2012.10371 {{citation}}: |access-date= requires |url= (help)CS1 maint: date and year (link)

Rincon, P. (October 28, 2011), Faster-than-light neutrino experiment to be run again, BBC, retrieved October 28, 2011

"Science in action", World Service, BBC, February 23, 2012, retrieved February 23, 2012

Seife, C. (2000), "CERN's gamble shows perils, rewards of playing the odds", Science, 289 (5488): 2260, doi:10.1126/science.289.5488.2260

Shiga, D. (December 8, 2011), "Neutrinos give US best shot at post-Tevatron glory", New Scientist, retrieved December 8, 2011

T2K statement on the OPERA anomaly (neutrinos travel faster than light), T2K Collaboration, October 20, 2011, retrieved December 4, 2011

"Tachyon", Encyclopaedia Britannica: Encyclopaedia Britannica Online, Encyclopaedia Britannica Inc., November 21, 2011, The existence of the tachyon, though not experimentally established, appears consistent with the theory of relativity, which was originally thought to apply only to particles traveling at or less than the speed of light

"Upstream from OPERA: extreme attention to detail", CERN Bulletin, October 10, 2011, retrieved November 20, 2011

"U.S. scientists to test findings that neutrinos defied physics' basic tenet", International Business Times, September 28, 2011, retrieved October 9, 2011

Wright, A. (2011), "It's a mystery", Nature Physics, 7 (833), doi:10.1038/nphys2143, As the particle physics community struggles to understand the OPERA experiment's seeming detection of superluminal neutrinos, anomalous results from other neutrino experiments are also under scrutiny. The LSND experiment, which ran at Los Alamos National Laboratory in the 1990s, found evidence of neutrino oscillations that didn't tally with the standard model of three neutrino species, or with other experimental data. And MiniBooNE, at Fermilab, has seen excess events that could support a particular explanation of the LSND anomaly [...sterile neutrino]

Further reading

Peer reviewed publications

Template:Hidden infoboxes

Retrieved from "https://en.wikipedia.org/w/index.php?title=2011_OPERA_faster-than-light_neutrino_anomaly&oldid=486892665"