# What is the meaning of short baseline experiments?

When trying to find the meaning of "short baseline" concept I came across the definition of a long baseline, described as "neutrinos are detected after traversing macroscopic distances".

So I presume that a short baseline experiment must imply that particles traveled a microscopic distance but this doesn't seem to agree with other statements that state that "the distance of the detector from the target is approximately 1km ". On this same page, it is stated that short baseline experiments are $$\lt 1$$km long.

This is still a macroscopic distance, hence these two statements seem to contradict each other, and the latter one seems to not have sources to check it is correct.

Could anyone tell me which is the proper definition of a short baseline experiment?

• Remember that those neutrinos are travelling at only a hair less than the speed of light. For an object moving so fast 1km is a short baseline. Aug 28, 2020 at 10:52
• That makes perfect sense, but then is the 1 km the standard by which these experiments are defined. Meaning, $\lt 1$ km, short baseline , $gt 1$ km , long baseline? Aug 28, 2020 at 10:53
• It is context dependent i.e. the meaning of short depends on the system you are studying. The word short has no precise technical definition and means whatever the group of scientists in question agree amongst themselves that it means. Aug 28, 2020 at 10:54
• A long baseline neutrino experiment is one in which neutrino mixing has a chance to occur at a detectable level. A short baseline is the opposite. Mixing depends on $L/E$ so for high energy neutrinos from accelerators 'short' baselines can be longer than for low energy neutrinos from reactors. Aug 28, 2020 at 11:40
• Out of curiosity, is "short baseline" a term used exclusively in neutrino experiments, or does it characterize particle detections in general? Aug 16, 2022 at 18:50

## 1 Answer

Given that the probability of transition is obtained: $$P_{\nu_\alpha \to \nu_\beta}(L, E) = sin^22\vartheta sin^2(1.27 \frac{\Delta m^2[eV^2]L[km]}{E[GeV]})$$ On the other hand, $$\Delta m$$ is fixed by nature. Therefore, in the experiment, the ratio of length to energy is important to us. And we categorize the experiments accordingly:

SBL = Short Base Line, LBL = Long Base Line, VBL = Vary Long Base Line, ATM = ATMospheric neutrino experiments, and SOL = SOLar neutrino experiments.

P.S. You can find more details in chapter 7 of Fundamentals of Neutrino Physics and Astrophysics - Carlo Giunti and Chung W. Kim