Oops-Leon is the name given by particle physicists to what was thought to be a new subatomic particle

Subatomic particle

In physics or chemistry, subatomic particles are the smaller particles composing nucleons and atoms. There are two types of subatomic particles: elementary particles, which are not made of other particles, and composite particles...

 "discovered" at Fermilab

Fermilab

Fermi National Accelerator Laboratory , located just outside Batavia, Illinois, near Chicago, is a US Department of Energy national laboratory specializing in high-energy particle physics...

 in 1976. The E288 collaboration, a group of physicists led by Leon Lederman who worked on the E288 particle detector

Particle detector

In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify high-energy particles, such as those produced by nuclear decay, cosmic radiation, or reactions in a...

, announced that a particle with a mass

Mass

Mass can be defined as a quantitive measure of the resistance an object has to change in its velocity.In physics, mass commonly refers to any of the following three properties of matter, which have been shown experimentally to be equivalent:...

 of about 6.0 GeV

GEV

GEV or GeV may stand for:*GeV or gigaelectronvolt, a unit of energy equal to billion electron volts*GEV or Grid Enabled Vehicle that is fully or partially powered by the electric grid, see plug-in electric vehicle...

, which decayed into an electron

Electron

The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...

 and a positron

Positron

The positron or antielectron is the antiparticle or the antimatter counterpart of the electron. The positron has an electric charge of +1e, a spin of ½, and has the same mass as an electron...

, was being produced by the Fermilab particle accelerator

Particle accelerator

A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...

. The particle's initial name was the greek letter Upsilon

Upsilon

Upsilon is the 20th letter of the Greek alphabet.  In the system of Greek numerals it has a value of 400. It is derived from the Phoenician waw. The name of the letter is pronounced in Modern Greek, and in English , , or...

 (). After taking further data, the group discovered that this particle did not actually exist, and the "discovery" was named "Oops-Leon" as a pun

Pun

The pun, also called paronomasia, is a form of word play which suggests two or more meanings, by exploiting multiple meanings of words, or of similar-sounding words, for an intended humorous or rhetorical effect. These ambiguities can arise from the intentional use and abuse of homophonic,...

 on the original name (mispronounced

English pronunciation of Greek letters

This table gives the common English pronunciation of Greek letters using the International Phonetic Alphabet It is the pronunciation of the ancient Greek names of the Greek letters using the English teaching pronunciation...

 ˈjuːpsɨlɒn) and the first name of the E288 collaboration leader.

The original publication was based on an apparent peak (resonance) in a histogram

Histogram

In statistics, a histogram is a graphical representation showing a visual impression of the distribution of data. It is an estimate of the probability distribution of a continuous variable and was first introduced by Karl Pearson...

 of the invariant mass

Invariant mass

The invariant mass, rest mass, intrinsic mass, proper mass or just mass is a characteristic of the total energy and momentum of an object or a system of objects that is the same in all frames of reference related by Lorentz transformations...

 of electron-positron pairs produced by proton

Proton

The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

s colliding with a stationary beryllium

Beryllium

Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...

 target, implying the existence of a particle with a mass of 6 GeV which was being produced and decaying into two leptons. An analysis showed that there was "less than one chance in fifty" that the apparent resonance was simply the result of a coincidence. Subsequent data collected by the same experiment in 1977 revealed that the resonance had been such a coincidence after all. However, a new resonance at 9.5 GeV was discovered using the same basic logic and greater statistical certainty, and the name was reused (see Upsilon particle

Upsilon particle

The Upsilon meson is a flavorless meson formed from a bottom quark and its antiparticle. It was discovered by the E288 collaboration, headed by Leon Lederman, at Fermilab in 1977, and was the first particle containing a bottom quark to be discovered because it is the lightest that can be produced...

).

Today's commonly accepted standard for announcing the discovery of a particle is that the number of observed events is 5 standard deviation

Standard deviation

Standard deviation is a widely used measure of variability or diversity used in statistics and probability theory. It shows how much variation or "dispersion" there is from the average...

s (σ) above the expected level of the background. Since for a normal distribution of data, the measured number of events will fall within 5σ over 99.9999% of the time, this means a less than one in a million chance that the apparent resonance would be caused by a statistical fluctuation. Using this standard, the Oops-Leon "discovery" would never have been published.