Monday, December 02, 2013

Unconstrained MSSM: LSP is pure Higgsino or pure wino

There are several interesting hep-ph papers today, especially those about supersymmetry, but I chose to highlight
LHC and dark matter phenomenology of the NUGHM
by Maria Eugenia Cabrera, Alberto Casas, Roberto Ruiz de Austri, Gianfranco Bertone (Amsterdam, Madrid, Valencia). They calculate a probability distribution for various masses of electroweak superpartners given the current accelerator and dark-matter constraints (and numerical observables).

They work within NUGHM which is a rather generic MSSM with "non-universal gaugino and Higgs masses". This subset of the MSSM parameter space is much less constrained than e.g. CMSSM.

Most of the paper offers us various calculations and graphs of the most likely values of masses of dark matter particles (the lightest superpartner, the LSP) and its close cousins that are light enough.

This figure (Figure 2) is probably the most representative figure in the paper that encodes the main results.

Click the image to zoom it in.

It shows the calculated 2D posterior probabilities for six different combinations of two masses. What can you see in the graph?

You may see that the "viable spots" are very small. Some people may spin this fact negatively (most of the a priori options are excluded!) – because they like to spin things negatively, especially things related to supersymmetry (or string theory). But the localization is really a good news. It shows that there are surviving regions in NUGHM and their smallness means that the resulting theory – NUGHM – is highly predictive.

The first graph among the six shows the masses of the lightest neutralino, the LSP \(\chi^0_1\), and the second lightest neutralino \(\chi^0_2\); they omit the tildes. The surviving place is composed of two very bright spots; the left one (lighter one) is sharper (more likely). These regions are said to agree with the reasons why "focus point supersymmetry" might be preferred, something that e.g. Nima would probably dislike.

Both spots, especially the lighter one, have the two masses almost equal to each other. This near-degeneracy is arguably incompatible with a bino admixture because there's just "one bino" that has no good reason to be degenerate with anyone else. It turns out that the left spot describes a nearly pure Higgsino LSP\[

m_{\chi^1_0} \approx 1\TeV, \quad m_{\chi^2_0} \approx m_{\chi^1_0}

\] while the second, right spot describes a nearly pure wino LSP with\[

m_{\chi^1_0} \approx 2.4\TeV, \quad m_{\chi^2_0} \approx m_{\chi^1_0}+\varepsilon

\] where the second neutralino might be a bit larger, after all. The second picture shows that the lighter top squark is less sharply determined, between \(1\) and \(10\TeV\) in the lighter spot and \(2\) and \(30\TeV\) in the heavier spot.

The diagonal shape of the third picture means that the left-handed and right-handed up squarks are predicted to be nearly degenerate, with the shared mass between \(3\) and \(30\TeV\) or so. All the scalar superpartners etc. are arguably sent towards "dozens of teraelectronvolts" which may be a politically correct codeword for "de facto infinity". This situation of the heavy scalars differs from the predictions for the neutralinos – the calculations seem to boldly imply "their masses are lower than a finite upper bound".

The bottom row of the three pictures is really showing the same thing as their upper counterparts – but the calculations used different prior probability distributions. The two rows are sufficiently similar to one another so that one could argue that the dependence on the priors isn't too strong – which is good news.

These masses are relatively heavy and the LHC might have trouble to see this heavy electroweak superpartners although in the scenarios highlighted by this research, the electroweak superpartners would be the most accessible ones by the LHC. However, the authors say that the two spots could be visible by the next generation of the XENON (and LUX?) underground dark matter search experiments.

Note that XENON and LUX turned out to be the big "No" experiments – showing that all the "Yes" experiments must have seen some other overlooked background effect although no one exactly understands what these background effects are. However, LUX and XENON may give a "Yes" answer soon, too. It would be interesting news but we would still face the risk that they're just seeing their own, more refined phantom events that don't really display dark matter.

So even if and when these strongest underground experiments start to say "Yes", it may take some time for the dark matter case to be established as "Yes".

Off-topic: In five years or so, will deliver your order by a drone in less than 30 minutes if you're at most 10 miles from their warehouse; just be sure to click at the PrimeAir button. For orders exceeding $10, they will send the B2 Stealth Bomber with the U.S. secretary of defense on board, too. The B2 has advantages for people in apartment buildings – it will make it unnecessary to break your window for the package to get into your apartment. Instead, they may bombard and demolish the apartments above yours. The only barrier preventing from launching the service tonight is a stamp by the bureaucrats allowing them to bombard the buildings.

McDonald's will prepare flying robots that will deliver roasted pigeons directly to your mouth. Too bad, the closest translation of the Czech idiom "kingdom where roasted pigeons are flying to your mouth" to English is the mundane phrase "the land flowing with milk and honey" – quite boring and lacking the Czech degree of industrialization. ;-)


  1. Hahaha, nice off topic LOL :-D

    So I will probably order a nice Christmas Relativity-Nutshell bomb soon ;-P

    The kingdome with with roasted pigeons flying into your mouth is called "Schlaraffenland" in German ;-)

    LEO gives "Cocckaigne" (sounds like something Lenny Susskind and friends use to write nice papers), "land of milk and honey", and "land of plenty" ... yawn, the first one is most plausible ...

    Thanks for explaining the results of this paper, I always like reading such things here :-)

    What does non-universal gaugino and Higgs masses mean?

  2. They named a street after one of the two Boston Marathon bombers?! Sick people, drop a JDAM on them.

  3. kashyap vasavadaDec 2, 2013, 3:37:00 PM

    Again a nice summary Lubos. Question. Just as quarks bind and form baryons, do squarks also are supposed to form sbaryons? They may have lower mass than squarks(?).

  4. In English, they probably call it Cockaigne because there's always enough cocaine for everyone.

  5. Dear Kashyap, supersymmetry is a generator of a symmetry and therefore a "derivative" so it obeys the Leibniz rule.

    So the superpartner of the baryon - something you might call a sbaryon - really contains just one squark and the remaining particles in it are ordinary squarks. Recall that for the derivative,

    (udd)' = u' d d + u d' d + u d d'

    holds. The prime may be interpreted quite literally as a supersymmetry variation, i.e. the superpartner of the primed object. On the LHS, you have a sbaryon. The right hand side is a superposition of baryons where one quark is replaced by its squark.

    Still, all these particles (like sbaryons) are almost certainly heavier than ordinary particles (baryons) because each superpartner or squark has to be heavier than any quark. If sbaryons contain a squark inside, it's like a baryon containing the top quark - a very heavy "core" that becomes the primary interesting part of the (s)baryon and all the mess around is just some mandatory universal QCD jelly.

    It's a good idea to avoid the trap of combining the description in terms of elementary particles and those involving the mesons or baryons; the latter is only OK at low energies and for baryons containing light quarks only. The (s)baryons with very heavy particles like the top quark or the squarks have physics that is mainly the physics of the heavy elementary particles inside.

  6. No, they named a street after the first president of independent Chechnya (Ichkeria) who, by the way, was a former Soviet airforce general and certainly not an Islamist:

  7. Thanks for this really good summary of this interesting paper.

    Could you please, please, increase the frequency of posts such as this one, about hep-th and hep-ph papers, especially those regarding String Theory and Supersymmetry?

    I am also very curious about which were the other "several interesting hep-ph papers today"?

  8. One typo ? rest ordinary quarks.

  9. "kingdom where roasted pigeons are flying to your mouth"
    Stuffed with creole sausage is centerpiece to our annual Thanksgiving dinner. Spectacular. Ships in a Dry Ice styrofoam biomailer.

    TeV dark matter must be stable against decay. A high kinetic temperature is required for homogeneous distribution to fit the Tully-Fisher relation vs. galactic radius and beyond (re atmospheric pressure vs. altitude). 1 Tev is about 1100 amu. No atomic nucleus is an efficient kinetic transfer.

    Theory carefully redefines itself to be untestable. If the vacuum is not strictly isotropic to fermionic matter (parity violations, symmetry breakings, Chern-Simons), Noether's theorems could sub-parts-per-billion leak for conservation of angular momentum as Milgrom acceleration. This is testable in bench top apparatus to one part in 20 trillion. Looking would ruin everything, yes?

  10. An extraordinary swath of female beauty extends from Persia through the Ukraine. Dump the ideology and embrace capitalist exploitation. If you're feeling clean and wholesome, advertising has the cure - plus royalties.

    A lowly Cuban streetwalker under Fulgencio Batista and the US Mafia was wealthier than near anybody under Fidel Castro. The US naval base in Subic Bay, Philippines was expelled in 1991. The surrounding Sodom embraced the economic purity of a Somalia refugee camp. God save us from do-gooders, ideologues, priggs, and politicians

  11. Dear Dimension10, this background is actually the "newer one" than the snowflakes. ;-)

    At various moments, I was thinking about discussing *every* hep-ph and hep-th paper of the day but I've grown out of it because I don't think that the demand is sufficient to justify the work and time spent. Sorry.

  12. "Ukraine would be a pretty bad reason for a conflict" - sure. A usual strategy is to subdivide a "pretty good reason for a conflict" into ten smaller ones, each of which is a pretty bad reason on its own. You get your wish in ten small steps instead of a huge dangerous one. Been there.

  13. Apologies, Jiří, I don't understand what you want to say.

    Just to be sure, I surely don't want a conflict between Russia and the EU, quite on the contrary, and I even tend to think that none of the two sides really wants such a development.

    So why should someone look for tricks or ten smaller steps needed to ignite such a conflict?

    My point was that an unwanted and unexpected conflict could emerge if Europe were trying to insensitively intervene into places like Ukraine – but I still believe that even in that case, it would remain "non-violent", at least for some time.

  14. Ah so desu ka?

    Sorry about that, dear people of Lviv. No hard feelings, eh? Accidents may happen, etc. etc.

  15. Daijobu desu, shinpai shinaide kudasai.

    In fact, let me tell you of a scene I witnessed in Lviv just over a week ago.

    A group of us was going for a walk in the centre of the city. Near the statue of prince Daniel (the founder of Lviv) we saw a crowd of people with blue flags with lots of stars on them: I quickly guessed they were EU fags (I actually forgot such a thing existed and this reminded me). The crowd was quite large and peaceful but soon it got even even larger as it was joined by much more noisy crowd of people with flags like this:

    Their looks and chants did not seem to fit the image of EU supporters and I quickly guessed who they were. I even noticed a couple of flags that looked like this:

    though the people who carried them did not look nearly as cute. I later confirmed on the Wikipedia that my guess what that flag was, was correct.

    The film director in our group (a Jew born in Slovakia, who escaped after the Soviet invasion on 1968 to the West and has lived in Switzerland) was very curious so left us to talk to some of the demonstrators. I met him later that evening for a drink. He told me that he talked to one of the people the Svoboda supporters and asked him if he was in favour of Ukraine joining the EU. "No" he said. "We have only joined these people because like they we are against the government". "But we want Ukraine to become be independent both of Russia and the EU. If we join the EU we will be ruled by Jews".
    After talking more to this guy the film director not only discovered that he was an-anti semite of the worst kind one can find anywhere but also that he had a Jewish father and had lived for some time in Israel.
    The film director was laughing and shaking his head over this. It is indeed a weird country (or maybe not so much after all...)

  16. I do hope you will find some more time to post regards SUSY and some of your "stringy" stuff too. Many of the blogs and "popular" writers are declining.

    I am enjoying your many years of posts, though. As I learn more on these subjects I am able to appreciate more and have realized just how much you have to offer. When I first came across TRF not quite two years ago I did not know how much of that which is posted and published elsewhere is simply false.

    I know those who spend time on this blog on subjects which you see little demand will join me in suggesting that the quality of the demand not the quantity is what we hope is more important.

    I am not suggesting you should stop posting other subjects. It is in fact the broad range of topics that make this blog my daily fascination. Mysl je hrozná věc na odpad. Yours is not.

  17. I heard a jew (old guy with a kippa) in Paris a couple of years ago who was against the state of Israël. I was surprised. He thought jewish people shouldn't have a fixed land...

  18. Less surprising than it seems. At the extreme of this phenomenon is Naturei Karta:

    Not only are they against the State of Israel, but often support Holocaust deniers, meet with and praise people like the former Iranian president Ahmedinejad and the American black racist Louis Farrakhan, etc., etc. One of their members served as a "minister for Jewish Affairs" in Arafat's "cabinet".

    What the motives of these people are you can only guess. But perhaps they remember (or instinctively understand the point being made in the quote below, from the world's "leading expert" on this matter:

    "I'm convinced that there are Jews in Germany who've behaved correctly—in the sense that they've invariably refrained from doing injury to the German idea. It's difficult to estimate how many of them there are, but what I also know is that none of them has entered into conflict with his co-racialists in order to defend the German idea against them. I remember a Jewess who wrote against Eisner in the Bayrischer Kurier. But it wasn't in the interests of Germany that she became Eisner's adversary, but for reasons of opportunism. She drew attention to the fact that, if people persevered in Eisner's path, it might call down reprisals on the Jews. It's the same tune as in the Fourth Commandment. As soon as the Jews lay down an ethical principle, it's with the object of some personal gain!"

    (Adolf Hitler, conversation on December 1, 1941 - from Hugh Trevor Roper's "Hitler's Table Talk").

  19. Oh Lumo yes,

    I can guess that it must feel frustrating when you feel that there is not enough positive response to your nice technical theoretical physics posts.
    But you can see there are people who would dearly miss them, if you would sop adding new such jems to the already existing TRF treasure :-)

    I immensely like your pedagogical technical articles, and even thouse more targetted at your colleages if which I dont understand every detail (but I do slowly understand more from keep learning), for some reason keep sticking in my head.

    Just yesterday I was reading about a baby example about stringy enhancement of the gauge group U(1) to SU(2) in the Zweibach book. This made me happily remember that you wrote about the broader topic of stringy enhancements of gauge groups too in a nice TRF article not too long time ago :-). I will have to retrieve and reread it now.

    So please keep up the good work and the nice gems coming, they are very precious to some people here ;-) :-)

  20. Those in Ukraine who are pushing for EU should look in what they may be
    getting themselves in. Best case scenario:a second fiddle to the Germans
    and French. Worst case scenario: Greece.

    I cringed when I heard that Ukraine gave up
    nuclear weapons. That was the (hopefully temporary) end of its
    independence. Restore the nuclear deterrent and believe in yourself. It
    is not through others (NATO, EU, US or Russia) will you achieve
    greatness and prosperity, but only through yourself.

  21. Seems to me that this is nothing more than a cynical and tasteless geo-political move to
    separate Russia and the Ukraine. I mean, why else would the EU be
    rejecting trilateral talks between Russia/EU/Ukraine? Why does it have
    to be an either-or situation? The Western media continues distracting
    from the actual reasons the Ukrainian government won't sign on the
    dotted line by instead focusing on "Putin's bullying" When in fact, it's
    the other way around.

    The association agreement has been so
    heavily misrepresented that many have been led to believe that this is
    about a membership to the EU, instead of about a trade agreement with
    the EU. How else can you explain the
    chants of “freedom” and “democracy” from protesters and their supporters
    when the actual deal being offered would only accelerate the Ukraine’s
    death spiral in terms of sovereignty and self determination? I also have
    the suspicion that the agreement is being
    heavily misrepresented in the Ukrainian media as well, by focusing all
    the rage on Russia and either ignoring or downplaying the tangible and
    logical reasons as to why Yanukovych won’t sign it.

  22. Wow. Thanks Lucretius. I didn't know about this Naturei Karta.

  23. Who knows what motivated the old guy. Perhaps he imagined himself to be living more than a century ago, during the time of the First Zionist Congress. In 1897 I would have been opposed to zionism, too. Crazy people with about as much chance of succeeding as the folks wanting to make Esperanto the common language for everyone. History, however, turned out to be far crazier than them and, essentially, proved them right.

    Or maybe he was worried about your reaction, knowing how anti-Israel many Europeans are. This reminds me of an old joke. Shmuel and Itzik are blindfolded and taken to the prison yard where they are about to shot. The leader of the firing squad asks them if they have a final request to make. Itzik spits out, "Yes, boy. You will bring me one of your expensive Turkish cigarettes and light it for me." Aghast, Shmuel turns to him and says, "Itzik! Don't make trouble."

  24. Lubos, you wrote a very nice post about the Munich Agreement. At that time, Europe would rather leave that small Czechoslovakia to that nice Mr. Hitler rather than to risk a conflict. Maybe what we see is not a resurrection of a Russian imperialism. Let's hope.

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