Neutrino08 Day 2d

K. Lesko introduced the multidisciplinary big cavern DUSEL proposal for the Homestake mine. Construction would take 6 to 8 years and a hopeful timeline is 2012-2018. Funds for concept proposals will be announced in October. The perfectly antipodean J. Gomez-Cadenas decided to start in 2016, now that we were into the swing of living in the future. He discussed superbeams at 1-4 MW and Beta beams, which would be pure neutrino beams.

Maltoni chose to spend 1/3 of his talk on the LSND problem and the apparent requirement of sterile neutrinos, which he explained were ruled out in 2+2 gen models by solar and atmospheric results, ruled out in 3+1 by short baseline data, ruled out in the 3+2 case (which attempted to reconcile LSND and MiniBooNE) by appearance and disappearance data, and ... well, he reckons it's all ruled out.

The last afternoon talk (before a 'generous' 10 minute break before the short evening talks) by Shaevitz discussed NuSOnG, an exciting generation III, TeV scale Fermilab neutrino scattering project using 800 GeV protons from Tevatron. It would have pure $\nu$ or pure $\overline{\nu}$ run modes and a possibility of a sizable tau neutrino fraction in the beam dump. It complements the LHC (see 0803.0354). Schedule estimate: 2009 proposal submission to 2016 data taking.

Neutrino08 Day 2c

H. Minakata continued with 2 possibilities, (i) $\theta_{13} > 3$deg, in which case conventional superbeams and megaton water detectors should work and (ii) small $\theta_{13}$, which would require new beam technologies, although liquid argon technology could change the situation. He promised to mention unconventional physics, but was forced to skip that section when the chair meanly rang the bell a little early. For varying E, he mentioned a possible 100 kiloton argon facility (3 or 4 times more sensitive than water Cherenkov detectors). For varying L, a test of CP violation would best use a low energy, short L setup.

Moving on to T2K, a 300km baseline Tokai to Kamioka project: I. Kato sketched the aim of observing $\theta_{23}$ and $\Delta m_{23}^{2}$ via muon neutrino disappearance with the help of the J-PARC accelerator. Achievable precision is apparently 0.01 in $\textrm{sin}^{2} 2 \theta$ and $< 10^{-4}$ for $\Delta m^{2}$. Installation and commissioning is on schedule: the LINAC at 181 MeV had good beam stability in Jan '07, the beam line tunnel was completed in Dec '06 and the main ring synchrotron is expected to be operational in 2009. After 5 years at SuperK at 0.75 kW they expect from 103 events (for 0.1 $\textrm{sin}^{2}$) to 10 events (for 0.01).

Despite the excellent IT support, R. Ray had to fight a Mac vs Bill Gates battle (which some people blamed on Fermilab) before commencing his talk on NOvA. This is a second generation NuMI beam line experiment requiring an accelerator upgrade to 700 kW beam power. A surface detector would be placed at Ash River, 810 km away. This requires a 6 storey, football field sized building on a site needing 40 ft of blasting in solid granite! A top cover of concrete/barite would shield the detector, which is a liquid scintillator in homemade highly reflective PVC cells. He stressed the importance of complementarity in experiments and comparisons of multiple results. For example, NOvA with Daya Bay and Chooz can determine if $\nu_{3}$ couples to the muon or tau neutrino (at 95% confidence). They expect a 36% event efficiency for electron neutrinos.

Future neutrino beams at J-PARC and Fermilab were discussed by Kajita and Saoulidou. For J-PARC, a Korean detector would give a 1000km+ baseline. Rubbia talked about proposed megaton detectors, for which there is a positive general consensus after reports in the US, Japan and Europe. In the 100 to 1000 kt range, one needs precise tracking and good calorimetric information. A feasibility study will be carried out 2008-2009. One interesting possibility is supernovae observation: the estimate is for 2 antineutrino events per year at 10 megaparsecs (with a 5 megaton water Cherenkov detector). Deep-TITAND (see hep-ex/0110005) is a 1km deep modular steel proposal.

As a pathologically punctual person, I have observed that the bell needs to be rung loudly before each session as chatting participants demonstrate their enthusiasm to their colleagues by pretending not to hear the bell.

Neutrino08 Day 2b

Zukanovitch-Funchal gave an overview of mixings and masses, starting with a 1978 quote from Froggart and Nielsen which refers to neutrino oscillations as exotic. Two mass hierarchies are possible with current results, that is the mass of $\nu_{2}$ is closer to only one of the other 2 masses. Although 2-generation analyses worked well, a 3-generation analysis has been carried out since 2001 (see for instance Prog. Part. Nucl. Phys. 57(2006)742). Parameters have been approaching the tribimaximal mixing values. It is exciting that parameter determinations are weakly correlated and we are entering a precision era! Cosmological bounds were briefly mentioned: a combination analysis sets $\Sigma m < 0.19 eV$.

V. Datar described the status of INO, in particular the proposal for detectors (iron) at Pushep, which has a baseline of about 7000km from CERN. See hep-ph 0805.3474. If 1 megaton per year is achieved, then the hierarchy type may be determined. A prototype will be put together in Kolkata in about one month's time. Minakata's talk focussed on long baseline proposals, and he began with a nice picture of Darth Vader to represent our life in the Dark Ages. But if it turns out that $\theta_{13}$ is 'large' then the Dark Ages might end before Neutrino2010!

Sigh. Only half way through Day 2 and already I feel like I'm living on a planet of neutrino physicists, with more detector cities than I can name! Must get coffee and beer ...

Neutrino08 Day 2a

J. Raaf was first up today with a report on Super Kamiokande, a 50 kiloton water Cherenkov detector under 1km of rock. Solar neutrinos: the focus was on phase III (mid 2006 to late 2008) results using 2 data sets, (i) full (E > 6.5 MeV) and (ii) radon reduced (E > 5 MeV), which are expected to achieve a 60cm elastic scattering vertex resolution. Phase II results showed no correlation with solar activity nor any day-night asymmetry (measured at -0.063 with larger errors). Atmospheric: a re-analysis of phase I data looking for exotic effects can exclude many models.

H. Gallagher represented MINOS, a long baseline experiment based at Fermilab and a Minnesota mine 735km away. Analyses of both charged and neutral current events were done blind. There are about $10^{18}$ protons hitting the target per day at the main injector, and 92.9% of neutrinos produced are muon $\nu$. Charged case: new run 1 and 2 results indicate a $\Delta m^{2} = 2.43 \times 10^{-3} eV^{2}$ and $\textrm{sin}^{2} 2 \theta = 1.00$, or rather $> 0.90$ at 90% confidence. Neutral case: depletion of neutral events is expected in the far detector but no evidence for it was found, the bound being 17% in a 0-120 GeV range. Neutrino decoherence is disfavoured $5.7 \sigma$.

OPERA is a 730km baseline (from CERN) emulsion tracking device which hopes to observe $\nu_{\tau}$ events. Muon neutrino flux is optimized with L/E = 43 km/GeV. Rosa described the detector modules, constructed of scintillator strip target modules embedded in 31 walls, each built from up to 3000 custom bricks of layered emulsion and Pb sheets. See 0804.1985. The short 2007 run saw 38 triggered candidate events with (at the end) 64060 bricks. With a high intensity beam at about 200 events per week, it is expected that the new run (starting around June 16) will see 1.2 $\nu_{\tau}$ events.

Neutrino08 Day 1c

For a change of topic, we heard from J. Coller on coherent neutrino scattering, which is a Standard Model process not yet measured due to current limitations in detector technology. This group uses cryogenic bolometers and works in the Chicago sewer system! The cross section is the same for all standard neutrinos, so an observation of oscillations would imply the existence of sterile neutrinos. Applications include prospecting, planetary tomography, light WIMP searches and other dark matter phenomenology. DAMA results were also mentioned in a noncommittal yet humorous fashion.

Potzel discussed the antineutrino Mossbauer effect, which is a recoilless resonant emission from decays such as 3H $\rightarrow$ 3He. To achieve minimum recoil one considers situating sources and targets in metallic lattices. For the 3H/3He system it appears possible to achieve recoil free fractions of $f_{(3H)} \cdot f_{(3He)} = 0.07$ at low temperature, but the whole project has the potentially serious problem of lattice contraction and expansion due to different storage volumes for 3H and 3He.

The most charming accent award goes to T. Lasserre, who spoke very rapidly about Double Chooz in France. Supposedly systematic errors for the two 7m x 7m detectors have been reduced to 0.2% for proton count and 0.5% for detector efficiency. Data collection should begin in the next year and after 3 years they hope for at least 0.03 sensitivity in $\textrm{sin}^{2} \theta_{13}$. C. White spoke for Daya Bay and RENO. The Hong Kong experiment, which should be fully operational by 2011, uses 0.1% Gd doped liquid scintillator detectors and aims for an impressive 0.01 sensitivity in $\textrm{sin}^{2} \theta_{13}$.

Exhausted after microphone wallah duty, I desisted from note taking in the pizza and beer session, which started at 6.45pm. This was a long series of brief talks, chaired by the town crier with his bell, associated to posters.

Neutrino08 Day 1b

The afternoon's talks began with a report on the KamLAND antineutrino scintillator detector by Decowski. The antineutrinos come from 55 reactor cores throughout Japan, giving KamLAND an effective baseline of 180km. Current best values for the standard parameters, including solar neutrino results, are

$\Delta m^2 = 7.59 \times 10^{-5} (eV)^{2}$
$\textrm{tan}^{2} \theta = 0.47$

There is now a 6.2 terawatt upper limit on the (popular new crackpot idea of a) Earth's core georeactor. This was also discussed by McDonough, a real geochemist. He presented a beautiful introduction to the history of collaboration between physicists and geologists, from Lord Kelvin and Wiechert to the new potential of neutrino physics for geochemistry. One of the big questions in this field is the K/U ratio for Earth. Geoneutrinos result from U, K and Th $\beta$ decay chains. They form a small flux on top of the reactor background. To understand the mantle, this would best be investigated far from crustal regions, say near Hawaii deep under the ocean. Hanohano is an exciting proposal for a mobile detector, whose size is limited only by the requirement that the transporting barge fit through the Panama canal.

Neutrino08 Day 1a

C. Galbiati represents the Borexino experiment, which observes solar neutrinos in real time using a spherical scintillation detector. Both 7Be and pep neutrinos are good sources for exploring the so called vacuum-matter transition. New results for 192 days of data were announced in this morning's talk: the 7Be result is $49 \pm 3$ counts per day per 100 ton. This is in good agreement with the MSW-LMA oscillation prediction of around 48, and rules out the no oscillation scenario at $4 \sigma$ (arxiv preprint 0805.3843).

Galbiati began with a summary of the (old) standard solar model and its agreement with helioseismology, which is no longer in such good agreement since the new estimate for metallicity appears to be a factor of 2 different. Can neutrino physics explain this discrepancy? One would like to use CNO* neutrinos to measure the metallicity of the core of the sun.

The next speaker was H. Robertson from the SNO collaboration. This is a 12 meter diameter, 1000 ton heavy water detector, with outer water shields. It has operated in three phases: (i) $D_{2}O$ (ii) $D_{2}O$ plus salt and (iii) $D_{2}O$ with 3He detectors. In the final phase, 36 strings of 3He detectors were deployed at a total length of 398m.

R. Hahn then confronted chemically challenged physicists with a talk about radiochemical experiments, including an historical interlude on Ray Davis, who was the first to observe solar neutrinos. He discussed the SAGE and GALLEX experiments. New results are a better fit to the constant flux line than previous results.

J. Klein outlined future solar neutrino experiments, noting the current focus on real time observations. One major goal is to look at the metallicity problem. Did Jupiter or Saturn somehow steal metals from the planetary protosphere? Or is something else going on? The correct value for solar surface metallicity may be obtained from 0805.2013.

* think Chemistry when you see capital letters, except in the last post

Neutrino08 - Smirnov

The first (slightly) technical talk of Day One was by A. Smirnov, who began with a very entertaining explanation of his title: Where are we? Where are we going? He pointed out that there were 52 (relatively recent) neutrino papers on SPIRES-HEP with headings including the words where are we? Similarly, he found multiple papers in other HEP areas that used the same words. But String Theory only managed one hit. Do they not wonder where they are? He then showed a timeline of neutrino physics, from Rutherford to the present, which was marked mysteriously as being somewhere on a brane.

Comments on the standard picture followed, with brief mentions of nuclear physics, neutrino gases, solar neutrinos, supernovae, AGNs, GRBs, CP violation etc. A fascinating fact is the shift in publications indicated roughly by the diagram Smirnov also stressed that although the initial excitement in new neutrino physics moved around the idea of beyond the Standard Model physics, the situation was far from clear. He listed a few bottom up approaches to theory, such as the tribimaximal mixing. Actually, he cited Carl Brannen alongside Koide in a final note about nonperturbative approaches (perhaps I should give him Carl's blog url as a reference).

The talk went 15 minutes over time due to a sneaky tactic of lying through teeth promising to be on the last slide.

Neutrino08

Neutrino08 kicks off this afternoon in the Town Hall, with a reception and cultural performance. Whilst viewing the latest poster listing I noticed that none other than Professor Koide will be attending and his abstract is already available here. (Now I wish I had made a paper poster myself, although it is probably rude for the hosts to take up conference space).

Tommorrow morning kicks off with a lecture on Ernest Rutherford, followed by a talk entitled Where are we? Where are we going?, by A. Smirnov from ICTP. More later.

Mass Update

Carl Brannen has been surreptitiously posting Koide mass formulas for pi meson and (the lightest) rho meson triplets at PF. For $n = 1,2,3$ and that damned number $\delta \simeq \frac{2}{9}$, the square root mass eigenvalues (for the same choice of units) all take the form

$\lambda_{n} = v + 2s \cdot \textrm{cos} (\delta + \frac{2n \pi}{3})$

where the parameters $v$ and $s$ must be set to

lepton: $v = \frac{1}{\sqrt{2}} , s = 1$
pi: $v = \frac{6}{5} , s = \frac{-3}{4}$
rho: $v = \frac{10}{7} , s = \frac{-1}{3}$

Now I must find time to check these against the PDG data...

M Theory Lesson 192

Are the Foaming Loopies secretly doing String Theory at last? The latest paper by Markopoulou et al looks at ribbon graphs in two dimensions and three stranded diagrams in three dimensions. The three strands may be considered as tubes, much as in closed string diagrams. Then the open-closed string duality becomes a duality between 2d simplices and 3d ones. But how can this be? As a Poincare duality one exchanges 2d and 3d objects only in dimension 5, whereas this stringy duality is usually associated with 2-categorical structures. Fortunately, a moduli space perspective solves the mystery. The tube diagram for the tetrahedron is a 4 punctured sphere, the moduli of which is indeed two dimensional. The other two dimensional moduli space is the space of elliptic curves. These two moduli describe duality as envisaged by Grothendieck in his work on ribbon graphs for surfaces.

Hidey Holes

The cover story of the last issue of New Scientist talks about the last place you'd expect to find a black hole. Yet another story about higher dimensions at the LHC? No, as the first paragraph states:

As the outside of the star finally cools, like a dying ember, its outer layers are suddenly blown away into space. And there, uncloaked for the first time, is a monstrous black hole.

The article, based on this recent paper, discusses the work of the University of Colorado's Mitchell Begelman and colleagues (but of course not Louise Riofrio). Referring to the conservative star formation mechanisms discussed in the paper, Fulvio Melia from the University of Arizona says:

With these mechanisms, something unusual - even dramatic - has to happen to make them work. Somehow this has to happen in a matter of only a few hundred million years, whereas simulations with standard physics show that it should take billions.

Perhaps something else is going on here.

Oh Mini Me II

Tommaso Dorigo reports from PPC08 on a MiniBooNE talk by Zelimir Djurcic, including a discussion of the low energy excess.

Photonuclear absorption of photons from $\pi_{0}$ decays was found to be a source of events at low energy.

This apparently accounts for some of the excess. Coincidently, there is also available a new PI talk by Jeffrey Harvey, which discusses a low energy QCD (AdS inspired) computation for the MiniBooNE excess based on a novel meson field process which has been neglected in the background analysis (see this paper). Initial results show impressive, if only tentative, agreement with experiment. I am hoping to report further on this after talks by Stephen Brice and Sam Zeller at Neutrino08 next week.

M Theory Lesson 191

As one moves up in dimension, it quickly becomes difficult to draw all intersections. The tetrahedron comes from four sets, with single (orange), double (blue), triple (pink) and quadruple (green) intersections. This gives an Euler characteristic of $\chi = 4 - 6 + 4 - 1 = 1$ for the ball in three dimensional space. Observe that by alternating signs we lose the information that there are 15 (= 4 + 6 + 4 + 1) pieces of Venn diagram. An invariant that combines both pieces of information is the Pauli circulant

$A$ $B$
$B$ $A$

for $A = V + F$ and $B = E + I$ ($I$ meaning 3d pieces) in this three dimensional example. Recall that the eigenvalues of the Pauli matrix are $A - B$ and $A + B$, the first being $\chi$ and the second the subset counter. This works in all dimensions.