I may not be the right person to ask this question, but as far as I recall there are no reasons for a constraint one way or the other. In some models the LSP is lighter than twice h, so that the decay is enabled, subtracting observable decay modes to h and making things harder for the discovery of the latter, but this is only a detail.

A totally different question, which should not be confused with the issue of mass values, is the discovery reach. It is totally false that the heavier a body is, the harder it is to find it. This is only true with electron-positron accelerators, where we know what is. A cascade of squarks and gluinos to lsp’s and leptons and jets would be very easy to see even with gluino masses of 600 GeV at LHC, because gluinos interact strongly and they have a large cross section. Instead, a higgs might be harder to see even at 180 GeV, where the decay to four muons or four electrons would be a really clean signature. It is a matter of production rates, and masses are only part of the equation there.

Cheers,
T.

I seem to remember reading somewhere that the LSP, if it exists, was expected to be heavier than the Higgs*,but I encountered someone this week who believed that SUSY would be found before the Higgs and I was wondering if that was in fact possible/probable.

* I may have been confused about the difference between the Higgs and Higgsino here.

CDF, after years of running, manages to provide calibrated and reconstructed data to analyses in two-three months. I expect there will be several initial issues (but the trigger shouldn’t be one since we will be taking data at very low rates -although still saturating our processing bandwidth).

On the other hand, past experience at the Tevatron will help LHC experiments, and indeed some analyses have been worked out in detail with Monte Carlo simulated samples.

All in all, the winter 2009 conferences appear to me as a really ambitious, although possible, goal for the very earliest distributions.

Cheers,
T.

well, in some special points of the parameter space you would indeed get cascades of gluino decays with a striking signature. The cross sections are large – for the LM1 test point considered in the CMS physics TDR (M_0=60, M_1/2=250, tan(beta)=10, sgn(mu)=+, A0=0) the cross section is 49 pb at LO for 14 TeV cm energy, with squark mass of 560 GeV and gluino mass of 611 GeV.

Accounting for trigger (missing Et>200 GeV) and reconstruction efficiencies (13% total), and backgrounds (mainly from ttbar and QCD) this would provide a 5-sigma observation with just 6/pb at 14 TeV, and probably still less than 40/pb at 10 TeV.

Overall, if those 40/pb were all LHC got, it would be well enough to see a SUSY signal just out of Tevatron reach – the limit on gluinos is about 350 GeV right now. But how lucky do we think we are going to be ? The argument that you will win big money by betting just another chip, after you squandered your whole pile, is always tempting but seldom a true picture of reality.

Cheers,
T.

If there really are strongly interacting superpartners with masses just out of reach of the Tevatron, how hard will it be for the LHC to see them? Will 40 inverse picobarns and a few months to analyze them be enough?

of course I am intimidated! You do know the topic of tt xs measurements more than I do!

I can only tell you what my reasoning is: two days ago we approved in CMS an analysis based on 100/pb of data taken at 14 TeV, which claimed a S/N of the order of 90/1 in the dilepton final state with b-tagging, and a xs measurement with a statistical accuracy of 8%.

At 10 TeV I do not expect things to be very different. The S/N can be tuned to be close to that value by changing cuts, at the expense of statistics. Say you pay a factor of 1.5 in stats, plus take into account the x2.5 reduction from 100 to 40/pb. That is a factor of 4 in stats, or a factor of 2 in stat error –> 16%. The systematics will be dominated by efficiency uncertainties, b-tagging uncertainties, and luminosity. I take these to be at most another 15%. So we are looking at a 20% measurement.

Then, one takes the single lepton final state. We approved a result on this channel as well two days ago, but we only have signal and background numbers to extrapolate from in that case. It looks like the single lepton channel should provide a measurement with better statistical accuracy and similar systematics (background systematics are not a concern until one pushes accuracy below 10%).

Overall, the combination could indeed provide a 10-15% measurement with 2008 data. That, however, depends on how much work we invest in these studies. Despite the fact that 2009 data might make us eager to do better things with our time, though, I believe the determination of ttbar xs at 10 TeV is an important measurement -we could never again have that particular beam energy. So I predict that for cross sections we will indeed squeeze an accurate determination.

Cheers,
T.