LHCb results show generation non-Universality (non-SM)

In summary, the conversation discusses the recent publication of a measurement of the ratio of branching fractions for B¯¯¯0→D∗+τ−ν¯τ and B¯¯¯0→D∗+μ−ν¯μ decays at the LHCb experiment. The multidimensional fit to kinematic distributions resulted in a value of R(D∗)=0.336±0.027(stat)±0.030(syst) which is 2.1 standard deviations larger than the expected value from the Standard Model. This result, along with other measurements, suggests a tension in the Standard Model and will be further investigated in Run 2 of the LHC.
  • #1
ChrisVer
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This article suggests something was found and that today we will be able to find the paper online.
http://www.eurekalert.org/pub_releases/2015-08/uom-ess082615.php

I am eager to see what the found and at what significance...asking for extra experiments means that the significance they got was not high enough to consist an actual discovery(?). So nevertheless if someone sees the publication before I do, post it here please?

Nevertheless it would be cool... either for SUSYs (non-minimal coupling) or GUTs (like a NUGIM I guess)... although it's getting quiet tiring with the news they let to reach out the world (with a significance of >2std we are told that something new was discovered...I guess that's marketing)
 
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  • #2
Hey, Chris,
This is probably the arXiv version of the paper-
http://arxiv.org/abs/1506.08614
http://arxiv.org/abs/1506.08614
Still not online at PRL

Measurement of the ratio of branching fractions B(B¯¯¯0→D∗+τ−ν¯τ))/B(B¯¯¯0→D∗+μ−ν¯μ)


Abstract-
The branching fraction ratio R(D∗)≡B(B¯¯¯0→D∗+τ−ν¯τ)/B(B¯¯¯0→D∗+μ−ν¯μ) is measured using a sample of proton-proton collision data corresponding to 3.0\invfb of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode τ−→μ−ν¯μντ. The semitauonic decay is sensitive to contributions from non-Standard-Model particles that preferentially couple to the third generation of fermions, in particular Higgs-like charged scalars. A multidimensional fit to kinematic distributions of the candidate B¯¯¯0 decays gives R(D∗)=0.336±0.027(stat)±0.030(syst). This result, which is the first measurement of this quantity at a hadron collider, is 2.1 standard deviations larger than the value expected from lepton universality in the Standard Model.
 
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  • #3
I also checked that but I was told (and later figured out by myself) that it was old (late June and not ends of August).
 
  • #4
Looks like a false alarm.

LHCb publishes important results on their public page before random news websites get them. Nothing there. Also, CERN would make a press release.

eurekalert.org refers to Brian Hamilton as one of the leading analyzers, which matches the arXiv preprint websterling found, and the description fits as well. It is also in agreement with a different recent news directly linking this (and mentioning the same publication date).
2.1 sigma significance is nothing. There are multiple 2-sigma-deviations, but those measurements are not independent.
 
  • #5
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  • #6
dukwon said:
The result is right there on the LHCb public page, under "25 May 2015: An intriguing anomaly."

http://lhcb-public.web.cern.ch/lhcb-public/#RDst
Right, but 2.1 sigma is not a significant result. Although some "scientific" disciplines believe it would be.
The 3.9 sigma combination is mainly driven by BaBar analyses 2012 and 2013.
Something to watch for Run 2 of the LHC, along with RK, P´5 and B0→ϕμμ
For sure.
Add ##H \to \mu \tau## to the list, although it is hard (but not impossible) to get that without violating muon decay constraints.
 
  • #7
It's hard to say anything right now with 2.1 sigma, I would suggest let's just wait and see when more data come out.
 
  • #8
mfb said:
The 3.9 sigma combination is mainly driven by BaBar analyses 2012 and 2013.

And is that good or bad?o_O
 
  • #9
It means the LHCb result is not contributing very much to the average.
2016 data should help, and by 2018 LHCb might be much more precise than the other experiments if the systematics can be reduced sufficiently.
 
  • #11
And multiple other measurements with a ~2 sigma tension all in the same direction, but those have correlated systematics so they could have a common source.
Run 2 of the LHC will certainly be interesting.
 
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1. What is the LHCb experiment?

The LHCb experiment is a particle physics experiment located at the Large Hadron Collider (LHC) at CERN (European Organization for Nuclear Research) in Switzerland. It is designed to study the properties of a fundamental particle called the beauty quark (also known as the "b-quark"), and other particles containing b-quarks, in order to better understand the fundamental forces and particles that make up our universe.

2. What are LHCb results showing about generation non-Universality?

LHCb results have shown evidence for a phenomenon known as "non-Universality" in the behavior of particles containing b-quarks. This means that the way these particles interact and decay is not consistent across different generations (or types) of particles, contrary to what is predicted by the Standard Model of particle physics.

3. What does "non-SM" in the results mean?

"Non-SM" in the results refers to the Standard Model (SM) of particle physics, which is the current theoretical framework that describes the fundamental particles and forces in our universe. The LHCb results show evidence for behavior that is not predicted by the SM, indicating the need for new or revised theories to explain this phenomenon.

4. Why is generation non-Universality important?

Generation non-Universality is important because it challenges our current understanding of the fundamental particles and forces in our universe. It suggests that there may be underlying principles and interactions that we have yet to discover, and could potentially lead to new discoveries in the field of particle physics.

5. What are the implications of these results?

The implications of these results are still being studied and debated by the scientific community. It could potentially lead to the development of new theories to explain the observed phenomenon, or it could require revisions to the existing Standard Model. These results also provide valuable insights into the behavior of particles and their interactions, helping us to better understand the fundamental nature of our universe.

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