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I 5 Higgs-like bosons -- natural supersymmetry required?

  1. Sep 21, 2016 #1
    MSSM and nMSSM require 5 higgs like bosons in addition to the 126 GEV the SM predicts.

    thus far LHC has not found any of them.

    what masses are predicted for Natural SUSY for these additional higgs and how much of a problem is it that the LHC has not found them?

    if natural SUSY is correct should additional higgs have been found in LHC run 2?
     
  2. jcsd
  3. Sep 22, 2016 #2

    mathman

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    Maybe. However, the masses of the additional Higgs bosons are guesswork right now.
     
  4. Sep 22, 2016 #3

    Vanadium 50

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    No, it predicts five in total.
     
  5. Sep 22, 2016 #4
    given 1 higgs has a mass of 126 gev, what are the range of values for the other 4 predicted higgs masses?
     
  6. Sep 23, 2016 #5

    ohwilleke

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    What the LHC has done has created mass exclusion ranges for various prospective extra Higgs bosons. Specifically, a positively charged Higgs boson (H+), a negatively charged Higgs boson (H-), a pseudo-scalar Higgs boson (A) and an extra scalar Higgs boson (either H or h depending on whether the one at 126 GeV is the heavier one or the lighter one).

    There are really no predictions regarding the other Higgs masses. They are free parameters in the model. All we have are experimental exclusions.

    Exclusions as of 2013 can be found at https://cds.cern.ch/record/1556867/files/ATL-PHYS-SLIDE-2013-391.pdf

    To summarize, as of that time, a heavy Higgs was excluded from 145 GeV to 710 GeV; A was excluded up to masses of about 200 GeV, charged Higgs were excluded up to 160 GeV. Almost all of those limits have grown larger over time.

    One way for an extra Higgs to hide is for it to be degenerate with the 126 GeV Higgs in mass. But, the observed Higgs is so purely scalar than there can't be a degenerate mass A.

    A 2015 summary is here: https://cds.cern.ch/record/2117949/files/ATL-PHYS-PROC-2015-206.pdf but has no "quotable" limits.

    The particle data group summarizes limits for neutral extra Higgs here: http://pdglive.lbl.gov/Particle.action?node=S055 (it is quite conservative due to the model dependency of the limits since the couplings of extra Higgs bosons are uncertain, if they exist).

    The particle data group limits for charged Higgs bosons are here: http://pdglive.lbl.gov/Particle.action?node=S064 and are also far too conservative.

    A preprint search for 2HDM (two Higgs doublet models) in the experiment subsection would probably reveal more up to date papers with more rigorous limits than PDG does.
     
  7. Sep 23, 2016 #6
    dear olwilleke, what kind of LHC experimental setups can prove that the Glashow-Weinberg-Salam Higgs as modelled by Higgs, Kibble, Guralnik, Hagen, Brout and Englert is correct? I read that the mass terms in the Higgs can come from other ways like the Coleman-Weinberg mechanism, etc.. If the latter is proven. Do they withdraw the Nobel Prize of Peter Higgs?
     
  8. Sep 26, 2016 #7

    ohwilleke

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    What the LHC can do is prove that the observed particle has all of the properties of the Standard Model Higgs boson. It has done a very good job in a very short time of doing just that. It has shown that it has the right quantum numbers to a very high precision. It has shown that the couplings that have been documented are the predicted ones to within a very modest margin of error. It is in the process of demonstrating that it is produced in all of the predicted ways. The width of the Higgs boson resonance has been constrained to a far smaller range of values than had been expected to be possible at this point due to some clever techniques.

    Even if one or another detail of the properties of the Higgs boson turn out to be not exactly as predicted, Peter Higgs absolutely deserves his Nobel Prize for coming up with an idea so close to the mark forty years in advance. Nobody faults Newton for not discovering General Relativity when none of the evidence available at the time would have made it possible for him to do so. Nobody faults Maxwell for not discovering quantum electrodynamics. A scientist's job is to move our understanding forward so that the next generation can stand on the shoulders of giants. Peter Higgs meets that very high bar.
     
  9. Sep 26, 2016 #8
    what would be a reason then to build a $10 billion higgs factory one proposed in Japan, an ep collider, if the LHC can do that.

    for $10 billion why not build a more powerful 100 GEV+ 50-100km hadron collider?
     
  10. Sep 26, 2016 #9
    do these other Higgs suffer from same higgs hiearchy problem that the SM 126 gev higgs does?

    wouldn't multiple higgs interact both with one another and with SM particles + SUSY partners?
     
  11. Sep 26, 2016 #10

    ohwilleke

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    For my druthers, $10 billion would be better spent on space telescopes (including gravitational wave detectors) than on a new collider of any kind.
     
  12. Sep 26, 2016 #11
    maybe there are SUSY partners just beyond LHC energies but within 100 TEV collider range. verifying SUSY might be more important to particle physics than space telescopes
     
  13. Sep 26, 2016 #12

    ohwilleke

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    Nobody knows because nobody has ever seen any evidence that they exist and there are several varied hypotheses regarding their properties (unlike the SM Higgs whose properties were completely determined by its mass).
     
  14. Sep 26, 2016 #13
    if natural SUSY and by extension MSSM and nMSSM were realized in nature, what can be said on these other higgs and their interactions with SM + SUSY on purely theoretical grounds
     
  15. Sep 26, 2016 #14

    ohwilleke

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    Even if SUSY did exist at those energy scales, it wouldn't be very useful and it is not like the laws of the universe are going anywhere. And, if SUSY exists anywhere, it is almost certainly not "just beyond LHC energies" because if it were, there would be a lot more anomalies in the LHC data because some observables are sensitive to much higher energy phenomena. We might not know just what was around the corner, but we would know that something was amiss. For SUSY to have no meaningful impact on LHC scale physics it has to be way over the mountains, across the desert and out across the sea, not just around the corner.

    In contrast, we know for a fact that we are observing BSM physics with telescopes today that give rise to dark matter phenomena (dark energy is not really BSM since it can be fully explained through GR with the cosmological constant). And, we have myriad ways that we can narrow the range of theories that can fit the data associated with this BSM physics simply by having better instrumentation. Why spend our money on science that might, just possibly maybe reveal new physics when we can spend it on physics that will definitely reveal BSM physics of some kind and the only question is what kind?
     
  16. Sep 26, 2016 #15

    ohwilleke

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    Not much. Even natural SUSY, MSSM and nMSSM offer lots of wiggle room and choices, in addition to having way more free parameters than the already ugly SM.
     
  17. Sep 26, 2016 #16
    ed witten for one is a fan of building the chinese collider.

    "
    With a circumference of 50 to 100 km, however, the proposed Chinese accelerator Circular Electron Positron Collider (CEPC) will generate millions of Higgs boson particles, allowing a more precise understanding.

    "The technical route we chose is different from LHC. While LHC smashes together protons, it generates Higgs particles together with many other particles," Wang said. "The proposed CEPC, however, collides electrons and positrons to create an extremely clean environment that only produces Higgs particles," he added.

    The Higgs boson factory is only the first step of the ambitious plan. A second-phase project named SPPC (Super Proton-Proton Collider) is also included in the design-a fully upgraded version of LHC.

    LHC shut down for upgrading in early 2013 and restarted in June with an almost doubled energy level of 13 TeV, a measurement of electron volts.

    "LHC is hitting its limits of energy level, it seems not possible to escalate the energy dramatically at the existing facility," Wang said. The proposed SPPC will be a 100 TeV proton-proton collider.


    If everything moves forward as proposed, the construction of the first phase project CEPC will start between 2020 and 2025, followed by the second phase in 2040.

    "China brings to this entire discussion a certain level of newness. They are going to need help, but they have financial muscle and they have ambition," said Nima Arkani Hamed from the Institute for Advanced Study in the United States, who joined the force to promote CEPC in the world.

    David J. Gross, a US particle physicist and 2004 Nobel Prize winner, wrote in a commentary co-signed by US theoretical physicist Edward Witten that although the cost of the project would be great, the benefits would also be great. "China would leap to a leadership position in an important frontier area of basic science," he wrote.

    http://www.dailygalaxy.com/my_weblo...universe-so-far-the-standard-model-seems.html

    Nima Arkani Hamed Ed Witten and David Gross thinks China should build a 100 TEV scale collider presumably with Chinese money

    perhaps the US and Russia and EU can build telescopes ;)-)

    perhaps a 100 TEV collider is needed to create dark matter and explore other BSM physics.

    2040 is a long time from now :'(
     
  18. Sep 26, 2016 #17
    SUSY is invoked to explain the higgs fine-tuning, but all those free parameters MSSM nmmsm has seems to also be fine tuning so as to avoid conflict with experiment.
     
  19. Sep 28, 2016 #18

    ohwilleke

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    Absolutely.
     
  20. Sep 28, 2016 #19
    the SM has a fine tuning problem with the higgs stability and theta in QCD. if there is an axion, that would explain why QCD theta is zero, which leaves 1 fine tuning problem, the higgs.

    SUSY MSSM and nMSSM, no SUSY has been seen by tevatron, ep colliders, ilc, LHC colliders. no SUSY seen in neutron, electron EDM or rare decays. no gluinos and squarks produced in proton colliders. LHC sees no SUSY no rare decay rates deviate from SM values.
    no SUSY dark matter observed.

    so SUSY MSSM and nMSSM has 120 parameters, and each has to be fine tuned to avoid the above constraints.

    so in effect the SUSY hypothesis may solve 1 fine tuning in the higgs sector, by introducing 5 higgs, and 120 parameters that need to be fine tuned to avoid conflict with experiment plus another set of particles "hidden sector" involved in SUSY-breaking, which might have additional fine tuning issues. occam's razor would suggest that SM is more parsimonious than SUSY.

    and the LHC has seen no evidence of natural SUSY that would explain higgs stability
     
  21. Sep 28, 2016 #20

    ohwilleke

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    "Fine tuning" is not a problem, it is a category error that looks like a problem only in the minds in misguided theoretical physicists. More humble physicists recognize that the laws of nature and its physical constants are what they are and are not subject to adjustment. The amount of sheer brainpower and time and money that has been spent thinking otherwise is a travesty.
     
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