T**E
发帖数: 1892 | 1 核心提示：9月，意大利格兰萨索国家实验室公布OPERA中微子实验打破光速的消息，立
刻引起全球广泛关注。但当时多数物理学家都对实验结果持怀疑态度。11月17日，来自
OPERA的研究人员发布新的实验数据，确认了之前的结果。
9月，意大利格兰萨索国家实验室公布OPERA中微子实验打破光速的消息，立刻引起全球
广泛关注。但当时多数物理学家都对实验结果持怀疑态度。
11月17日，来自OPERA的研究人员发布新的实验数据，确认了之前的结果。来自OPERA的
Dario Autiero说：“此次的结果比之前的结果要稍微好些。”他还补充说，之前合作
组里的一些成员希望用更多时间检验结果，从而拒绝在原初论文上签字，目前他们已全
部签字。其中一位成员、德国汉堡大学的Caren Hagner表示，实验的精确性得到了改进
，统计分析更为可靠了，并且由OPERA里的不同小组进行了重复。
然而，OPERA之外的科学家仍然表示怀疑。他们寄希望于由一个独立的实验来进行重复
。其中最受期待的是美国费米实验室“主注入器中微子振荡搜寻”（简称MINOS）实验
。针对OPERA的最新结果，费米实验室发表声明说，该实验室正在升级有关系统，2012
年初应该可以获得相关结果。（来源：科学网） | T**E
发帖数: 1892 | 2 Neutrino experiment affirms faster-than-light claim - November 18, 2011
An updated version of this story is now available (see 'Neutrino experiment
replicates faster-than-light finding').
It is a remarkable confirmation of a stunning result; but most physicists
remain skeptical. That seems the most probable outcome of a release of new
data expected on 17 November from researchers with the Italian OPERA
collaboration, who say they have confirmed their controversial finding that
flighty subatomic neutrinos can travel faster than light.
“It’s slightly better than the previous result,” says OPERA’s physics
coordinator Dario Autiero of the Institut de Physique Nucleaire de Lyon in
France (pictured). He adds that most of the members of the collaboration who
declined to sign the original paper because they wanted more time to check
the result have now come on board. One of these is Caren Hagner of the
University of Hamburg in Germany. She says not only has the experiment's
precision been improved, the statistical analysis is more robust and has
been replicated by different groups within OPERA not just the original team.
“We gained much more confidence,” Hagner says.
OPERA (which stands for Oscillation Project with Emulsion-tracking Apparatus
) made headlines in September with a claim to have clocked neutrinos
traveling faster than light, a result at odds with Albert Einstein’s well-
established Special Theory of Relativity, which sets light as the ultimate
cosmic speed limit. The group used a pulsed beam of neutrinos produced by a
particle accelerator at CERN near Geneva which traveled some 730 kilometers
to Gran Sasso near L’Aquila, Italy where the particles were detected.
The result was highly statistically significant but following Carl Sagan’s
well-known mantra that “extraordinary claims require extraordinary evidence
”, most physicists expressed doubts. While OPERA appeared to have conducted
its data-taking and analysis carefully, there was rampant speculation about
possible sources of error and some made claims of mistakes that the
collaboration brushed off.
One set of concerns centered on the relatively long timescale – 10.5
microseconds, or 10.5 millionths of a second – of the proton pulses
produced at CERN that result in the neutrino pulses OPERA detects. OPERA did
not know whether individual neutrinos received at Gran Sasso corresponded
to protons early or late in the proton pulse, creating uncertainty around
their detection of them. In October OPERA therefore asked CERN to generate
shorter proton pulses lasting just 3 nanoseconds. They have now recorded 20
events in the new data run and say that they have reached a similar level of
statistical significance to the first time around, with the neutrinos again
reaching Gran Sasso 60 nanoseconds faster than a light beam would do.
OPERA expects the new result to rule out uncertainties due to the long
timescale of the proton pulses. But concerns about the experiment’s use of
the Global Positioning System to synchronize clocks at each end of the
neutrino beam are unlikely to be as easily allayed, The use of GPS is novel
in the field of high energy and particle physics and the same system was
used for both the original experiment and the new run. Hagner also adds that
she’d like to see the time measurement checked using another part of the
detector, to increase confidence further.
For most physicists outside the collaboration, however, the key test will be
replication by an independent experiment. The one best placed to
independently confirm or refute OPERA’s result is MINOS (the Main Injector
Neutrino Oscillation Search) at Fermilab in Batavia, Illinois. In response
to the latest OPERA result, MINOS issued a statement saying it is upgrading
its timing system to match OPERA's precision and might have preliminary
results obtained using the existing system that are relevant to assessing
OPERA's results as soon as early 2012.
"OPERA is to be congratulated for doing some important and sensitive checks
but independent checks are the way to go," says Rob Plunkett, co-spokesman
for MINOS. | T*******y
发帖数: 6523 | 3 Thanks for sharing!
I have a friend in Physics who told me that Einstein proved that light speed was actually a threshold speed. If the particle has a lower speed, then it can't exceed the light speed. But if the particle has a higher speed, then it can't drop below the light speed. What moves at light speed remains light speed. What do you think about it?
【在 T**E 的大作中提到】
: 核心提示：9月，意大利格兰萨索国家实验室公布OPERA中微子实验打破光速的消息，立
: 刻引起全球广泛关注。但当时多数物理学家都对实验结果持怀疑态度。11月17日，来自
: OPERA的研究人员发布新的实验数据，确认了之前的结果。
: 9月，意大利格兰萨索国家实验室公布OPERA中微子实验打破光速的消息，立刻引起全球
: 广泛关注。但当时多数物理学家都对实验结果持怀疑态度。
: 11月17日，来自OPERA的研究人员发布新的实验数据，确认了之前的结果。来自OPERA的
: Dario Autiero说：“此次的结果比之前的结果要稍微好些。”他还补充说，之前合作
: 组里的一些成员希望用更多时间检验结果，从而拒绝在原初论文上签字，目前他们已全
: 部签字。其中一位成员、德国汉堡大学的Caren Hagner表示，实验的精确性得到了改进
: ，统计分析更为可靠了，并且由OPERA里的不同小组进行了重复。
| d*****n
发帖数: 3033 | 4 这是同组的人吧
【在 T**E 的大作中提到】
: 核心提示：9月，意大利格兰萨索国家实验室公布OPERA中微子实验打破光速的消息，立
: 刻引起全球广泛关注。但当时多数物理学家都对实验结果持怀疑态度。11月17日，来自
: OPERA的研究人员发布新的实验数据，确认了之前的结果。
: 9月，意大利格兰萨索国家实验室公布OPERA中微子实验打破光速的消息，立刻引起全球
: 广泛关注。但当时多数物理学家都对实验结果持怀疑态度。
: 11月17日，来自OPERA的研究人员发布新的实验数据，确认了之前的结果。来自OPERA的
: Dario Autiero说：“此次的结果比之前的结果要稍微好些。”他还补充说，之前合作
: 组里的一些成员希望用更多时间检验结果，从而拒绝在原初论文上签字，目前他们已全
: 部签字。其中一位成员、德国汉堡大学的Caren Hagner表示，实验的精确性得到了改进
: ，统计分析更为可靠了，并且由OPERA里的不同小组进行了重复。
| n*****n
发帖数: 5277 | |
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