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I think the "lines [of data]" should be more like "lines [of research]" or maybe [of inquiry] or something. What they mean, I think, is that the approaches from different directions will all converge on one answer. Your "[of data]" seems like not the right editorial insertion.

AFAIK, xenon (and argon too) are nice for this purpose because they're dense liquids with large atomic numbers. This makes nice, big targets for particles to smack into. In addition, their "ionization potentials" are low, which means that it doesn't take much energy to kick an electron away from the nucleus. This makes it easier for scintillations to happen, so you get a better scintillation yield. Argon is cheaper than xenon, but it has the problem that it's likely to be contaminated with the radioactive isotope Ar-39, and radioactive decay causes interfering events of its own.

To add to Blake's comments, the use of liquid targets is also motivated by ideas of scalability - if you want a bigger target, you just make a bigger tank. Things aren't quite that simple, of course - you need to ensure that the big tank is sufficiently low in radioactivity and has sufficient discrimination power to distinguish a dark matter signal from any radioactive backgrounds (e.g. from the glass of the light detectors which line the tank), but the collaborations involved are making excellent progress in these areas.

Argon is much like xenon for these purposes, but requires a significantly larger detector (due to the smaller atomic mass of argon) and should have vastly more discrimination power against backgrounds. The question is the balance between the extra discrimination power and the added radioactivity of the argon itself (though less radioactive sources of argon are being identified).

Very powerful background discrimination is the traditional strength of CDMS (the current world leader) and similar cryogenic detectors, but the construction of a large cryogenic detector array presents substantial challenges of its own.


I think the idea is that one set of data will exclude a certain range of dark matter parameters, then another set will exclude a different range, and another set another range --- and so on, until there is a very definite, small region of parameter space in which the dark matter particles must be living. Identifying that region will be seen as "detection" in the same way that determining the mass of the top quark counted as "detection."

The neutrino fraction should be 0.001 of the critical density, not 0.001 percent. This is assuming the sum of the three neutrino masses is about 0.05 eV/c^2.

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    • Heavy G
      The perfect pick-me-up when gravity gets you down.
      2 oz Tequila
      2 oz Triple sec
      2 oz Rose's sweetened lime juice
      7-Up or Sprite
      Mix tequila, triple sec and lime juice in a shaker and pour into a margarita glass. (Salted rim and ice are optional.) Top off with 7-Up/Sprite and let the weight of the world lift off your shoulders.
    • Listening to the Drums of Feynman
      The perfect nightcap after a long day struggling with QED equations.
      1 oz dark rum
      1/2 oz light rum
      1 oz Tia Maria
      2 oz light cream
      Crushed ice
      1/8 tsp ground nutmeg
      In a shaker half-filled with ice, combine the dark and light rum, Tia Maria, and cream. Shake well. Strain into an old fashioned glass almost filled with crushed ice. Dust with the nutmeg, and serve. Bongos optional.
    • Combustible Edison
      Electrify your friends with amazing pyrotechnics!
      2 oz brandy
      1 oz Campari
      1 oz fresh lemon juice
      Combine Campari and lemon juice in shaker filled with cracked ice. Shake and strain into chilled cocktail glass. Heat brandy in chafing dish, then ignite and pour into glass. Cocktail Go BOOM! Plus, Fire = Pretty!
    • Hiroshima Bomber
      Dr. Strangelove's drink of choice.
      3/4 Triple sec
      1/4 oz Bailey's Irish Cream
      2-3 drops Grenadine
      Fill shot glass 3/4 with Triple Sec. Layer Bailey's on top. Drop Grenadine in center of shot; it should billow up like a mushroom cloud. Remember to "duck and cover."
    • Mad Scientist
      Any mad scientist will tell you that flames make drinking more fun. What good is science if no one gets hurt?
      1 oz Midori melon liqueur
      1-1/2 oz sour mix
      1 splash soda water
      151 proof rum
      Mix melon liqueur, sour mix and soda water with ice in shaker. Shake and strain into martini glass. Top with rum and ignite. Try to take over the world.
    • Laser Beam
      Warning: may result in amplified stimulated emission.
      1 oz Southern Comfort
      1/2 oz Amaretto
      1/2 oz sloe gin
      1/2 oz vodka
      1/2 oz Triple sec
      7 oz orange juice
      Combine all liquor in a full glass of ice. Shake well. Garnish with orange and cherry. Serve to attractive target of choice.
    • Quantum Theory
      Guaranteed to collapse your wave function:
      3/4 oz Rum
      1/2 oz Strega
      1/4 oz Grand Marnier
      2 oz Pineapple juice
      Fill with Sweet and sour
      Pour rum, strega and Grand Marnier into a collins glass. Add pineapple and fill with sweet and sour. Sip until all the day's super-positioned states disappear.
    • The Black Hole
      So called because after one of these, you have already passed the event horizon of inebriation.
      1 oz. Kahlua
      1 oz. vodka
      .5 oz. Cointreau or Triple Sec
      .5 oz. dark rum
      .5 oz. Amaretto
      Pour into an old-fashioned glass over (scant) ice. Stir gently. Watch time slow.