(Very) Recent Results from K2K

JimHill

October 16, 2001

Abstract:

The most recently analysed data from the K2K experiment in Japan are presented. The experiment has accumulated approximately $3.9\cdot 10^{19}$ protons on target (p.o.t.), taking it to nearly 40% of its full proposed lifetime of $10^{20}$p.o.t.. The observed number of fully contained events with vertices in the fiducial volume disfavors the null hypothesis (no mixing) at approximately the $2\sigma$ level. The observed spectrum of single ring muon like events in that sample is inconclusive, but more consistent with the SK atmospheric neutrino best fit for oscillations than for the null hypothesis.

$\textcolor{blue}{\cal K} {\scriptsize 2}\textcolor{red}{\cal K}$ has published its first ``physics paper'' in PL-B¹ and posted it on the web as an e-print. (It was submitted in late February, 2001 and posted a few days later.)

Preface

This talk was presented at the 2001 Snowmass conference in Colorado, USA. It presents results from K2K representing its runs from June of 1999 through April, 2001. The 2001 running is continuing until July 11th. Two more years of running are essentially guaranteed; a third might be possible.

All the slides from the talks are reproduced with much narrative filled in. A few pictures are supplemented by links to pages with original pictures (and more of them!). A few figures might be added later to answer questions that come up during one talk or another. A copy of just the slides, but all of them, is available in PostScript or in pdf format. A copy of PostScript for each figure can be downloaded separately in a link below the appearance of the figure here.

For a rather general (if now somewhat dated) overview of the field of long-baseline experimentation, one can see a talk I developed in early 2001 a few months before our new data were added to the sample. For a lower level talk, I have a couple short things that I prepared to present to undergraduates: one for a ``teaching interview'' recently and one rather older one that I delivered at a local college near my hometown shortly after K2K began data taking in 1999.

Disclaimers:

(Download the above figure.)