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Highlights from the morning talks at PPC08 May 19, 2008

Posted by dorigo in astronomy, cosmology, news, physics, science.
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The conference on the Interconnections between particle physics and cosmology, PPC2008, started this morning in the campus of the University of New Mexico. The conference features a rather relaxed, informal setting where speakers get a democratic 30′ each (plus 5′ for questions), and they do not frown at the repeated interruptions to their talks by questions from a self-forgiving audience.

This morning I listened to six talks, and I managed to not fall asleep during any. Quite a result, if you take into account the rather long trip I had yesterday, and the barely 4 hours of sleep I could manage tonight. This is a sign that the talks were interesting to me. Or at least that I need to justify to myself having traveled 22 hours and spending a week in a remote, desertic place (sorry Carl).

Here is a list of the talks, with very brief notes (which, my non-expert readers will excuse me, I cannot translate to less cryptic lingo due to lack of time):

  • The first talk was by Eiichiro Komatsu, from Austin, who discussed the “WMAP 5-year results and their implications for inflation“. Eiichiro reviewed the mass of information that can be extracted from WMAP data, and the results one can obtain on standard cosmology from the combination of WMAP constraints and other inputs from baryon acoustic oscillations (which one derives from the distribution of galaxies in the universe), supernovae, HST data and the like. He discussed the flatness of the universe (it is very flat, although not perfectly so), the level of non-gaussianicity in the distribution of primordial fluctuations (things are about as gaussian as they can), the adiabaticity relation between radiation and matter (which can be tested by cross-correlations in the power spectrum), and scale invariance (when n_s is found to be smaller than one at 2-sigma level, and if combined with additional input from omega_baryons can go as low as 3.4-sigma below 1).
  • Riccardo Cerulli then talked about the “Latest results from the DAMA-LIBRA collaboration“. I discussed these results in a post about a month ago, and Riccardo did not show anything I had not already seen, although his presentation was much, much better than the one I had listened to in Venice. In short, DAMA members believe their signal, which now stands out at 8.2 standard deviations, and they stand by it. Riccardo insisted on the model-independence of the result, while confronted with several questions by an audience that wouldn’t be convinced about the solidity of the analysis and less so about the interpretation in terms of a dark matter candidate. DAMA has collected so far a statistics of 0.53 tons x year, and is still taking data. I wonder if they are after a day-night variation or what, since it does not make much sense to increase a signal whose nature is -this is sure by now- of systematic nature.
  • Rupak Mahapatra talked just after Riccardo about the “First 5-tower results from CDMS”, another direct search for dark matter candidates. I also discussed the results of their work in a recent post (I am surprised to be able to say that and rather proud of it), so I will also not indulge in the details here. Basically, they can detect both the phonons from the nuclear recoil of a WIMP in their germanium detector, and the charge signal. Their detectors are disks of germanium operated at 40 millikelvins. ON the phonon side there are four quadrants of athermal phonon sensors, where a small energy release from the phonon disrupts cooper pairs and the change in resistivity is easily detected. On the charge side, two concentric electrodes give energy measurement and veto capability. The full shebang is well shielded, with exotic materials such as old lead from 100-old ships fished out of the ocean (old lead is not radioactive anymore). The experiment tunes cuts of their signal region to accept about half event from backgrounds. They observed zero events, and set stringent limits on the mass-cross section plane of a WIMP candidate. They plan to upgrade their device to a 1000 kg detector, which will make many things easier on the construction side, but which will run into non-rejectable neutron backgrounds at some point.
  • Alexei Safonov talked about the “Early physics with CMS“. Alexei discussed the plans of LHC for the years 2008 and 2009, and the results in terms of collected luminosity that we can expect for CMS and ATLAS, plus the expectations for analyses of SUSY and other searches. He was quite down-to-earth on the predictions, saying that the experiments are unlikely to produce very interesting results before the end of 2009. In 2008 we expect to collect 40 inverse picobarns of 10 TeV collisions, while in 2009 from 7 months of running starting in June the expectation is of about 2.4 inverse femtobarns. It goes without saying that it is quite likely that data collected until the end of 2009 might be insufficient even for a standard model Higgs boson discovery.
  • Teruki Kamon talked about “Measuring DM relic density at the LHC and perspectives on inflation“. He pointed to a recent paper at the beginning of his talk: hep-ph/0802.2968. Teruki took in consideration the coannihilation region of SUSY, where there is a small mass difference \Delta M between neutralino and stau, making the two likely to interact and creating a particular phenomenology. This region of the parameter space at high tan(beta) can be accessed by searches for tau pairs, which arise at the end of the gluino-squark decay chain. Through a measurement of tau pair masses and endpoints the mass of SUSY particles can be determined with 20 GeV accuracy. In particular, the ratio of gluino to neutralino masses can be measured rather well. With just 10 inverse femtobarns of data Teruki claims that one can get a very small error on the two parameters M_0 and M_{1/2}. A final plot showing the resulting constraints on \Omega_\chi versus \Delta M raised some eyebrows, because it showed an ellipse while the model dependence on \Delta M is exponential (the suppression of the coannihilation goes as e^{-\Delta M/20}) and one would thus expect a fancier contour of constraints. In any case, if nature has chosen this bizarre manifestation, LHC experiments are likely to measure things accurately with a relatively small bounty of data.
  • U. Oberlack was the last one to talk, discussing “Dark matter searches with the XENON experiment“, another setup for direct dark matter detection. Xenon as a detector medium is interesting because it has ten isotopes which allow sensitivity to spin-independent and spin-dependent interactions of WIMPS with nuclei. In principle, if one detected a signal, changing the isotope mixture would make the measurement sensitive to the details of the interaction. Liquid xenon has a high atomic number, so it is self-shielding from backgrounds. The experiment is located in the gran sasso laboratories in Italy, and it has taken data with a small “proof of principle” setup which nevertheless allowed to obtain meaningful limits on the mass versus cross section plane. They plan to make a much larger detector, with a ton of xenon: since they can detect the position of their signals, and have a fiducial region which is basically free of backgrounds, scaling up the detector size is an obvious improvement since the fiducial region increases quickly. He showed a nice plot of the cross section sensitivity of different experiments versus time, where one sees three main trends in the past, depending on the technology on which experiments have been based. xenon as a medium appears to be producing a much better trend of sensitivity versus time, and one expects it will dominate the direct searches in the next future.

I will complement the above quick writeup with links to the talk slides as they become available…


1. carlbrannen - May 19, 2008

Tommaso, If my long comment on eating places in Albuquerque got thrown into the spam filter, places that will serve you food that is (a) inexpensive, (b) good, and (c) only available in New Mexico are, on the south side of the UNM campus (across Central street if I recall) is the Frontier Restaurant, which you can find by googling frontier restaurant Albuquerque. It is quite popular at UNM and will be crowded during meal times. I like to have their red chile tamales.

And I always end up with at least two meals at Monroe’s. Get the menu order #00 green chile cheeseburger, along with “taco fingers” as an appetizer and a sopapilla as desert (bite a corner off of it, and put a little honey inside of it, then eat it with your fingers).


Let’s see if this gets past the spam filter…

2. carlbrannen - May 19, 2008

Things to do in Albuquerque. I generally end up squiring nephews and nieces on at least one trip to a museum. There is one that is interesting to physicists, http://www.atomicmuseum.com/ . New Mexico is where atomic weapons were first invented and tested. You will probably find this museum memorable in a perhaps creepy way. But make sure they’re open, they were talking about moving the last time I visited.

The museum is next to “Old Town” which is the place that tourists visit in order to purchase useless but expensive doodads. There are places to eat there, but they are slightly touristy. The best places where the locals eat local food are where I just mentioned.

You can see a 3000m mountain east of the city. There is a tram that runs from the east part of the city up to the top. It runs all year long but gets the most use during skiing season. They claim that it’s the world’s longest aerial tramway. See http://www.sandiapeak.com/

Uh, try to avoid doing this trip on a windy day. In high winds, they will halt the thing and if they do this while you are on the peak you will be stuck there (or can hitch a ride down the east side of the mountain). Or worse, you will have a story to tell about the 12 hours you spent in a swaying gondola 300m in the air while the crowded tourists around you became sea sick – until you were finally rescued by something involving a National Guard helicopter and an air rescue sling.

This time of year, some of the cactus are in flower and if you have a camera these are worth seeking out. These are stunningly beautiful. The locals get used to them and a lot of them don’t even notice them. Remarkably, some of them will deny that cactus flowers even exist. Keep your eyes open.

By the way, the Albuquerque airport is unique in that it has several quite excellent places to eat.

3. loop - May 20, 2008

Regarding the DAMA results, I understand that the observed phase of the oscillations is compatible with the maximum being around June 2nd, time at which the velocity of the earth is aligned with the velocity of the sun while it travels around the galaxy. Do you have an idea how precise is this result? Can they exclude say peaking around June 21st which would point towards some solar source for their signal? Should someone repeat the observations in Australia?

4. Amara - May 20, 2008

Thanks for the overview of the talks you heard (so far). I’m impressed that you stayed awake too, after that grueling travel! And if you have a chance to chat with Riccardo Cerulli-Irelli, then please give my greetings. (His office was across from mine at IFSI, during my five years there, and he was very helpful to me in many administrative tasks too.)

5. dorigo - May 20, 2008

Hi Carl,

yes the first message had gotten caught by the (by now very aggressive) spam filter. Thank you so much for the advice. I will most certainly make good use of it.
I am presently debating with myself whether to go to sandia or take a balloon flight. As for the museum, I’ll do that.


PS just had dinner at Scalo, and was impressed by the food!

6. dorigo - May 20, 2008

Hi loop,

I think they find a result compatible with June 2nd at 1-sigma level. If I remember correctly (but I wouldnt bet on it) they fit something like 10 days before, with 10-day error. So indeed, June 21st might be excluded at 3-sigma.

Hi Amara,

I talked to Riccardo this morning (we had breakfast together and then I brought him to the conference with the car I rented). No doubt I will offer your greetings tomorrow.
Take good care of yourself!

7. Amara - May 20, 2008

Yup, the ultrasound today showed a very healthy Myrtle the extraterrestrial. Since it is a normal pregnancy now, I can consider it normal to continue to sleep my life away (my body is demanding 12 hrs/day of sleep) and to have waves of queasiness, especially during the submittal times of my NASA grant proposals. 😉

8. dorigo - May 20, 2008

Wow, you must be thrilled! Thank you for letting me know.
I know you know this already, but please don’t drink a single glass
or smoke a single cigarette. Alcohol levels have proven unhealthy even at extremely low doses.


9. forrest noble - May 20, 2008


I kinda have hopes for the WIMP experiment, as I mentioned before that slowed down neutrinos could, according to my hypothesis, interact more readily with matter and would be therefore perceived as a WIMP. Where, accordingly it might be the primary vector of pushing gravity.

As for dark matter, as I have also discussed before, I don’t think they have a clue. The methods described above seem worthless to me. If its a non-spinning neutral particle millions of times smaller than an electron, as I believe that it is, they cannot find it using present methods. Instead they can see the energy of countless millions of them every day of the week via interactions in the ZPF, since accordingly it would be a primary source of this observed energy.. Secondly, they show up as long strings of dark matter in particle collisions which are now called quark jets. At least thats the theory.

One big problem with theories today, I believe, as you mentioned by way of Gausian analysis, if there is no clear and valid concept model based upon observation first, then the mathematics will almost certainly be wrong.

your friend forrest

10. carlbrannen - May 20, 2008

The similarity between balloons and trams are that both involve gondolas. To my ear, “gondola” brings up images of Venice, Italy and gruesome accidents in Albuquerque.

The risks in taking a tram ride are fairly small. But balloons are definitely not very safe. They will explain this to you when they make you sign the agreement saying that they don’t owe money to your heirs. Baloons have no control surfaces.

Several people have been given the excitement of choosing between death by burning and sky diving without a parachute. Then there is the rather frequent interaction between balloons and high voltage power lines. Even if the pilot manages to dump the excess heat in the balloon at the right time to land it in an unpopulated part of the desert there is still the opportunity to have the basket tip over on landing, and unceremoniously dump the riders into a cactus patch.

In the deserts near Albuquerque, the cacti can grow 8 feet high. They are covered with spines up to about 2 inches long. When I was a boy, we found out, (the hard way) that these spines can go all the way through your hand. But it isn’t the big spines that you’ll be talking about. It’s the thousands of really tiny spines that will drive you insane trying to remove them. The doctors say that these are too small to see and will be exceedingly painful for most of a year. The big spines aren’t that easy to remove. Imagine being covered with thousands of them.

Needless to say, in Albuquerque, a large percentage of the children fall into a cactus. However, I know of no one who has done this twice. An advantage of growing up in a place like this is that I can instinctively walk through the desert without getting spines stuck into me. I also have the ability to hike many miles through the desert without running into any rattlesnakes (by avoiding the spots that they find attractive).

Now I’m up in the Pacific Northwest. Up here, you eventually discover that you can’t take a 50m short-cut through the undergrowth. The exceedingly delicious razor sharp raspberry bushes will cut your clothes right off you and leave you bloody from head to toe. The reason so many serial killers operate out here is that these bushes make great places to hide bodies. They must grow a half meter per day because if you don’t remove them from your yard they will take over in a couple weeks with 3/4″ thick branches and will have to be logged rather than cut down.

Let’s see, there’s one other accident that only happens at most once to someone in Albuquerque. You handle the spicy insides of chile pods (peeling them before cooking i.e.), get the juice on your hands but fail to very carefully wash your hands for a long time. Then you touch yourself in a private spot. Ooops.

11. dorigo - May 21, 2008

Lol Carl, you are a mine of bad stories 🙂 a minefield ?
Indeed, balloon rides are probably not that safe. You don’t hear people dying from that so frequently though. What are the odds ? 1 in 10000 ? 100000 per flight ? Looks harmless to me, but I agree – not worth it.

As far as cacti are concerned, I imagine you are paranoid about them: I would too… I think every part of the world has its dangers… I am thinking about “ricci di mare”, some animals that live on rocks underwater near the coast, covered with spines. You step over one, and you remember it for a long time…

I don’t think I’ll go to a balloon ride, the conference is too interesting after all!

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