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Anna Phan | USLHC | USA

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ICHEP 2012: Day Three

Today was another day of parallel talks. There was again six streams of talks where again the topics in each stream varied throughout the day. I would have loved to spend the day in the Higgs stream, listening to the new ATLAS, CMS, CDF and D0 results, however, I spent the day in the heavy flavour physics stream. This was because my talk was scheduled in this stream.

Today, on behalf of the LHCb collaboration, I presented measurements of \(B_s^0\) meson lifetimes. And because I can, I’ll summarise the results I presented for you all. *winks*

First off, I need to give you a bit of background regarding the \(B_s^0\) meson. As the \(B_s^0\) meson is neutral, it can transform, via the box Feynman diagrams on the left to its antimatter partner, the \(\overline{B}_s^0\) meson, and back again. If we look at and manipulate the equations governing the mixing and decay of the \(B_s^0-\overline{B}_s^0\) meson system we find that there are two \(B_s^0\) mass eigenstates, \(B_{s,H}^0\) and \(B_{s,L}^0\), with two different lifetimes, \(\tau_H = 1 / \Gamma_H\) and \(\tau_L = \Gamma_l\) with \(\Delta\Gamma_s = \Gamma_L – \Gamma_H\) and \(\Gamma_s = (\Gamma_L+\Gamma_H)/2\).

We can measure \(\Delta\Gamma_s\) and \(\Gamma_s\) through the analysis of the decay \(B_s^0 \to J/\psi \phi\) and access \(\tau_H\) and \(\tau_L\) from the measurement of the \(B_s^0\) lifetime in \(B_s^0 \to J/\psi f_0(980)\) and \(B_s^0 \to K^+K^-\) decays:

\(\Gamma_s = 0.6580 \pm 0.0054 \pm 0.0066\, {\rm ps}^{−1}\)
\(\Delta\Gamma_s = 0.116 \pm 0.018 \pm 0.006 \,{\rm ps}^{−1}\)
\(\tau_H \simeq \tau_{J/\psi f_0} = 1.700 \pm 0.040 \pm 0.026 \,{\rm ps}\)
\(\tau_L \simeq \tau_{KK} = 1.468 \pm 0.046 \pm 0.006 \,{\rm ps}\)

These results can all be shown as a function of \(\Delta\Gamma_s\) and \(\Gamma_s\) like below. You can see that all the results are fairly consistent, and the experimental combination overlaps all three individual experimental results. It is also consistent with the theoretical prediction of \(\Delta\Gamma_s\).

The measurement of \(B_s^0\) lifetimes and the information they provide regarding \(\Delta\Gamma_s\) is interesting as the value of \(\Delta\Gamma_s\) can be affected by physics beyond the Standard Model…

And that’s it for Day Three of ICHEP 2012 for me. Until Monday everybody!



2 Responses to “ICHEP 2012: Day Three”

  1. flashgordon says:

    I thought there might be a good reason to come back quickly and see if there’s some new physics; looks like I have to come back monday for “physics beyond the Standard Model”?

    It must be something else to go to a science conference and 1) you’re announcing your results and there’s like twelve others announcing their results, and then 2) you try to catch on to hear some others ideas/results, only there’s like seven others going at the same time!

    I remember when I was in the Navy up in Seatle area(Whidbey Island specificaly); i’d go to the local community college and I found “Science” and “Nature” magazines for the first time; i’d spend all day just reading all the exciting findings. Within a week, I’d find that there’s new issues each and every week! I’d go there each weak; i remember reading about non-equilibrium thermodynamics of cell structures; i grew up reading James Gleik’s “Chaos” and other chaos books and learn about Ilya Prigogine(I still wonder how self-organization science like chaos can be applied to understand quantum particles even though they say chaos theory doesn’t apply at that level; seems to me that photons are self-organising into electrons(and other quantum particles) and maybe some self-organisation works in terms of whether we see quantum particles as diffraction patterns or particles; but, chaos theory doesn’t apply! I still try to think about it though!). But, anyways, one of my favorite military days observations is how each week of doing my military work(as an avionic tech) it’s always the same boring work; nothing is ever new; it’s always saturated with military ethics(saluting, and just other military stuff). And, then, going to read the latest Science/Nature issues was always inspiring. The thing was you couldn’t tell these military people that tech work was boring! They all thought/think they’re such intellectuals!

    Maybe monday?!

  2. nsetzer says:

    Hey Anna, the Higgs talks were nice since essentially each channel got a 15 minute expose; however, I think I have to object to the last line of your post, as it appears you missed out on the poster session in the evening. This period was a nice time to talk one-on-one with the presenters. In addition, several of the Higgs channels had posters so it was a good time to catch up in case you missed the talks.

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