First direct observation of time-reversal non-invariance in the neutral-kaon system

TLDR: The first observation of time-reversal symmetry violation through a comparison of the probabilities of K 0 transforming into K0 and K 0 into K 0 as a function of the neutral-kaon eigentime t was reported in this article.

About: This article is published in Physics Letters B.The article was published on 1998-12-17 and is currently open access. It has received 190 citations till now. The article focuses on the topics: Strangeness.

Figures

Table 1 Summary of systematic errors

Frequently asked questions

Q1. What have the authors contributed in "First direct observation of time-reversal non-invariance in the neutral-kaon system" ?

0 the authors report on the first observation of time-reversal symmetry violation through a comparison of the probabilities of K 0 0 0 transforming into K and K into K as a function of the neutral-kaon eigentime t. 

Q2. How many electrons are identified with the NN?

The electron identification efficiency, obtained requiring that less than 2% of pions be misidentified aselectrons, is on the average 85%. 

Q3. What is the input to the NN .algorithm?

The inputs to the NN Ž .algorithm are the momentum of the particle, the energy loss in the two scintillators S1, S2 , the number of Ž .photoelectrons in the Cherenkov counter and the time of flight from the decay vertex to the first scintillator S1 . 

Q4. How many standard deviations are used to estimate the effect of an error in the normalization functions?

TIn order to estimate the effect of an error in the normalization functions, j and h, the authors change the value of the average normalization in the fit procedure by one standard deviation. 

Q5. What is the probability of the neutral-kaon lifetime?

The fitted momenta and vertices resulting from the 6C-fit determine the neutral-kaon lifetime with a precision which ranges from 0.05 t in the short lifetime region to 0.2–0.3 t in the long one. 

Q6. What factors can cause a distortion of the rates?

SA number of factors that can introduce a distortion of the rates must be considered: detection efficiencies, regeneration effects, background estimation and decay-time resolution. 

Q7. What is the CP w xviolation in the neutral-kaon system?

In the past, phenomenological studies based on the Bell-Steinberger relation have concluded that CP w xviolation in the neutral-kaon system is dominantly accompanied by CPT invariance and T violation 2 . 

Q8. What is the source of systematic error in the measurement of A?

An additional source of systematic error arises from the charge asymmetry in the background, owing to the different probabilities for a pq and a py to be identified as a positron and an electron, respectively. 

Q9. What is the asymmetry for the decay amplitudes?

The authors note that Im x is given by the value of the asymmetry for shortq Ž . ² exp:lifetimes while 4Re e is determined by the long lifetime values. 

Q10. What is the level of asymmetry in the background?

The level of this asymmetry has been determined using pions selected from minimum-bias events and is found to be Ž . ² exp: y33"1 %, leading to an uncertainty in A of "0.02=10 . 

Q11. what is the resulting systematic error on asymmetry?

The resulting systematic error on A is foundT to be "0.1=10y3.Ž .The experimentally obtained asymmetry see Section 4.4 is² exp: y3A s 6.6"1.3 "1.0 =10 .Ž .T stat syst Ž . Ž .This value is well compatible with 4Re e see Section 6 .