Comments on: Particle physics marches on

By: Small Things Considered | Cosmic Variance

Small Things Considered | Cosmic Variance — Thu, 04 May 2006 06:41:23 +0000

[...] See the MINOS website for more information. Sean did a post about it here. I thought that the radio segment was rather good, and informative for the non-physicist. Have a listen. You can look at lots of information and other links on the NPR site, and click the “listen” button for the radio piece. I very much like the tongue-in-cheek and rather self-aware editing in places. For example, when he’s talking about the neutrinos shooting down the beampipe (or some such action), there’s some realy corny special effects whizzing noises. Kestenbaum says, almost apologetically (as though he had an argument with a senior producer about putting this sound in, and lost), “That’s not the real sound” (but maybe there’s a hint of a smile in his voice, maybe?) [...]

By: Experimental sociology | Cosmic Variance

Experimental sociology | Cosmic Variance — Mon, 17 Apr 2006 15:10:08 +0000

[...] A little late, but I didn’t want to let slip this interesting discussion about the agonizing process of making experimental particle physics results ready for public consumption from Tomaso Dorrigo and Gordon Watts. You’ll recall that we mentioned a couple of weeks ago the new results from Fermilab’s Tevatron on B-mixing, a measurement that puts interesting new constraints on the possibilities for physics beyond the Standard Model. The first announcement was from the D0 (”D-Zero”) experiment; as Collin pointed out in the comments, the CDF experiment followed with their own results soon thereafter. [...]

By: JoAnne

JoAnne — Wed, 12 Apr 2006 06:12:31 +0000

Thomas, you make a good case and indeed many people have put all the constraints together and studied the supersymmetry parameter space in detail. The result is that supersymmetry is very elusive, particularly if you consider the general theory and not the very constrained case of minimal supergravity mediated SUSY. In the former (general SUSY), then no, there are no real constraints except for the kinematic limits from sparticle searches at colliders. In constrained models, one sign of the Higgsino mixing parameter (mu) is disfavored if the sparticles are relatively light (

By: Thomas Larsson

Thomas Larsson — Wed, 12 Apr 2006 06:03:55 +0000

Does anyone know how stringent constraints on SUSY are, if one takes all types of experiments into account? Wouldn’t one expect to see several things, e.g.

1. Sparticles
2. Light Higgs
3. Muon g-2
4. Permanent electric dipole moment
5. Proton decay
6. WIMPS
7. B_s mixing
and perhaps others. AFAIU, none of these experiments can rule out SUSY by themselves, but taken together they should provide much stronger constraints than each of them taken separately, no?

By: JoAnne

JoAnne — Tue, 11 Apr 2006 05:19:10 +0000

The Tevatron results on B_s mixing are smack dab in the middle of the Standard Model expectations, factoring in the remainer of the B-physics results. Quite disappointing, actually – us theorists were hoping for a much larger number!.

Nonetheless, there is significant play in the overall prediction due to uncertainties in theoretical quantities such as the B meson decay constant and bag factor. Due to this, I don’t see where this result will place any significant constraints on supersymmetry. Sorry, wish it were different myself. However, there are a few wilder theories that predicted maximal B_S mixing that will now be excluded.

By: Collin

Collin — Tue, 11 Apr 2006 05:00:50 +0000

I’m not exactly qualified to say anything about constraints on SUSY, though I’d be thrilled if someone (JoAnne?) would chime in with that. I’d also like to hear what this does for the Unitarity Triangle. Along with this measurement, CDF reported a measurement of |V_td|/|V_ts| = 0.208 +/- 0.008, a pretty significant increase in the precision of this quantity. Specifically, does this measurement improve the constraints on rho?

As for a comparison with the D0 result, it’s certainly consistant. But, the CDF result is much nicer, if a bit later. In their amplitude scan (basically, you scan a range of possible Delta(m_s) values, fit the oscillation data and measure a mixing amplitude; this should be 1 at the true value of Delta(m_s) and 0 otherwise), D0 found a 5 ps^-1 window where the data were inconsistant with 0 at a 90% CL. In comparison, CDF actually measured Delta(m_s) to better than +/- .5 ps^-1. If you wanted to put it in a 90% CL range to compare directly with D0, it’d be less than 1 ps^-1 and contained entirely within D0’s range, though certainly on the low side.

By: JoAnne

JoAnne — Tue, 11 Apr 2006 04:44:15 +0000

Ah, Collin – the importance of competition between 2 experiments! We have been waiting – for years – for this result which CDF in particular had promised very early on. Now that D0 announced it first, it seems that CDF suddenly is ready to go public too. I recall attending a talk, just last Fall, where CDF stated it would be awhile before they could measure B_s mixing, while D0 kept silent on the matter….

By: Sean

Sean — Tue, 11 Apr 2006 04:33:16 +0000

Collin, thanks for the update — I had heard that the CDF results were imminent. So what does that mean in comparison with the D0 results, and constraints on susy?

By: Collin

Collin — Tue, 11 Apr 2006 02:37:04 +0000

I just thought I’d let everyone know that at today’s Wine & Cheese seminar at Fermilab, CDF announced a measurement of Delta(m_s) in the B_s system of 17.33 with an error of about 2.5%.

By: Cyberspace Rendezvous :: Particle physics marches on :: April :: 2006

Cyberspace Rendezvous :: Particle physics marches on :: April :: 2006 — Fri, 07 Apr 2006 00:18:58 +0000

[...] For all you physics geeks out there: the group physicist blog Cosmic Variance talks about particle physics: Yesterday the MINOS experiment at Fermilab (Main Injector Neutrino Oscillation Search) released their first results. (More from Andrew Jaffe.) This is one of those fun experiments that shoots neutrinos from a particle accelerator onto an underground journey, to be detected in a facility hundreds of miles away â€” in this case, the Soudan mine in Minnesota. They confirm the existence of neutrino oscillations, with a difference in mass between the two neutrino states of Î”m2 = 0.0031 eV2. The neutrinos left Fermilab as muon neutrinos… [...]