Tagged: Tetraquarks? For real? Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 11:59 am on December 5, 2017 Permalink | Reply
    Tags: , , , , , , , Tetraquarks? For real?   

    From GIZMODO via FNAL: “Two Teams Have Simultaneously Unearthed Evidence of an Exotic New Particle” Revised to include the DZero result 

    FNAL II photo

    FNAL Art Image
    FNAL Art Image by Angela Gonzales

    Fermilab is an enduring source of strength for the US contribution to scientific research world wide.

    GIZMODO bloc

    Ryan F. Mandelbaum

    I can’t believe I’ve written three articles about this weird XI particle.

    A tetraquark (Artwork: Fermilab)

    A few months ago, physicists observed a new subatomic particle—essentially an awkwardly-named, crazy cousin of the proton. Its mere existence has energized teams of particle physicists to dream up new ways about how matter forms, arranges itself, and exists.

    Now, a pair of new research papers using different theoretical methods have independently unearthed another, crazier particle predicted by the laws of physics. If discovered in an experiment, it would provide conclusive evidence of a whole new class of exotic particles called tetraquarks, which exist outside the established expectations of the behavior of the proton sub-parts called quarks. And this result is more than just mathematics.

    “We think this is not totally academic,” Chris Quigg, theoretical physicist from the Fermi National Accelerator Laboratory told Gizmodo. “Its discovery may well happen.”

    Bust first, some physics. Zoom all the way in and you’ll find that matter is made of atoms. Atoms, in turn, are made of protons, neutrons, and electrons. Protons and neutrons can further be divided into three quarks.

    Physicists have discovered six types of quarks, which also have names, masses, and electrical charges. Protons and neutrons are made from “up” and “down” quarks, the lightest two. But there are four rarer, heavier ones. From least to most massive, they are: “strange,” “charm,” “bottom,” and “top.” Each one has an antimatter partner—the same particle, but with the opposite electrical sign. As far as physicists have confirmed, these quarks and antiquarks can only arrange themselves in pairs or threes. They cannot exist on their own in nature.

    Scientists in the Large Hadron Collider’s LHCb collaboration recently announced spotting a new arrangement of three quarks, called the Ξcc++ or the “doubly charged, doubly charmed xi particle.”

    CERN/LHCb detector

    It had an up quark and two heavy charm quarks. But “most of these particles” with three quarks “containing two heavy quarks, charm or beauty, have not yet been found,” physicist Patrick Koppenburg from Nikhef, the Dutch National Institute for Subatomic Physics, told Gizmodo back then. “This is the first in a sense.”

    The DZero collaboration at Fermilab announced the discovery of a new particle whose quark content appears to be qualitatively different from normal.

    The particle newly discovered by DZero decays into a Bs meson and pi meson. The Bs meson decays into a J/psi and a phi meson, and these in turn decay into two muons and two kaons, respectively. The dotted lines indicate promptly decaying particles.

    The study, using the full data set acquired at the Tevatron collider from 2002 to 2011 totaling 10 inverse femtobarns, identified the Bs meson through its decay into intermediate J/psi and phi mesons, which subsequently decayed into a pair of oppositely charged muons and a pair of oppositely charged K mesons respectively. Science paper in Physical Review Letters.

    With the knowledge such a particle could exist (and with the knowledge of its properties like its mass), two teams of physicists crunched the numbers in two separate ways. One team used extrapolations of the experimental data and methods they’d previously used to predict this past summer’s particle. The other used a mathematical abstraction of the real world, using approximations that take into account just how much heavier the charm, bottom, and top are than the rest to simplify the calculations.

    In both new papers published in Physical Review Letters https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.202002 and https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.119.202001, a stable four-quark particle with two bottom quarks, an anti-up quark, and an anti-down quark fell out of the math. Furthermore, the predicted particles’ masses were not quite the same, but similar enough to raise eyebrows.

    “As you notice, the conclusions are basically identical on a qualitative level,” Marek Karliner, author of the first study from Tel Aviv University in Israel, told Gizmodo. And while lots of tetraquark candidates have been spotted, this particle’s strange identity—including the added properties and stabilization from its two heavy bottom quarks—would offer unambiguous evidence of the particle’s existence.

    “The things we’re talking about are so weird that they couldn’t be something else,” said Quigg.

    But now it’s just a manner of finding the dang things. Quigg thought a new collider such as one proposed for China might be required.

    Rendering of the proposed CEPC [CEPC-SppC for Circular Electron-Positron Collider and Super Proton-Proton Collider]. Photo: IHEP [China’s Institute of High Energy Physics]

    But physicists are in agreement that the sometimes-overlooked LHCb experiment has been doing some of the year’s most exciting work—Karliner thought the experiment could soon spot the particle. “My experimental colleagues are quite firm in this statement. They say that if it’s there, they will see it.” He thought the observation could come in perhaps two to three years time, though Quigg was less optimistic.

    Such unambiguous detection of the tetraquark would confirm guesses from as far back as 1964 as to how quarks arrange themselves. And the independent confirmation from different methods have made both teams confident.

    “I think we have pretty great confidence that the doubly-b tetraquark could exist,” said Quigg. “It’s just a matter of looking hard for it.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    “We come from the future.”

    GIZMOGO pictorial

  • richardmitnick 4:00 pm on June 29, 2016 Permalink | Reply
    Tags: , , , , , , , Tetraquarks? For real?   

    From Symmetry: “LHCb discovers family of tetraquarks” 

    Symmetry Mag


    Sarah Charley

    LHCb. Courtesy of CERN

    Researchers found four new particles made of the same four building blocks.

    It’s quadruplets! Syracuse University researchers on the LHCb experiment confirmed the existence of a new four-quark particle and serendipitously discovered three of its siblings.

    Quarks are the solid scaffolding inside composite particles like protons and neutrons. Normally quarks come in pairs of two or three, but in 2014 LHCb researchers confirmed the existence four-quark particles and, one year later, five-quark particles.

    The particles in this new family were named based on their respective masses, denoted in mega-electronvolts: X(4140), X(4274), X(4500) and X(4700). Each particle contains two charm quarks and two strange quarks arranged in a unique way, making them the first four-quark particles composed entirely of heavy quarks. Researchers also measured each particle’s quantum numbers, which describe their subatomic properties. Theorists will use these new measurements to enhance their understanding of the formation of particles and the fundamental structures of matter.

    “What we have discovered is a unique system,” says Tomasz Skwarnicki, a physics professor at Syracuse University. “We have four exotic particles of the same type; it’s the first time we have seen this and this discovery is already helping us distinguish between the theoretical models.”

    Evidence of the lightest particle in this family of four and a hint of another were first seen by the CDF experiment at the US Department of Energy’s Fermi National Accelerator Lab in 2009.

    FNAL/Tevatron CDF detector
    FNAL/Tevatron machine
    FNAL/Tevatron map
    CDF; Tevatron; Tevtron map

    However, other experiments were unable to confirm this observation until 2012, when the CMS experiment at CERN reported seeing the same particle-like bumps with a much greater statistical certainty.

    CERN/CMS Detector
    CERN/CMS Detector

    Later, the D0 collaboration at Fermilab also reported another observation of this particle.

    FNAL/Tevatron DZero detector

    “It was a long road to get here,” says University of Iowa physicist Kai Yi, who works on both the CDF and CMS experiments. “This has been a collective effort by many complementary experiments. I’m very happy that LHCb has now reconfirmed this particle’s existence and measured its quantum numbers.”

    The US contribution to the LHCb experiment is funded by the National Science Foundation.

    LHCb researcher Thomas Britton performed this analysis as his PhD thesis at Syracuse University.

    “When I first saw the structures jumping out of the data, little did I know this analysis would be such an aporetic saga,” Britton says. “We looked at every known particle and process to make sure these four structures couldn’t be explained by any pre-existing physics. It was like baking a six-dimensional cake with 98 ingredients and no recipe—just a picture of a cake.”

    Even though the four new particles all contain the same quark composition, they each have a unique internal structure, mass and their own sets of quantum numbers. These characteristics are determined by the internal spatial configurations of the quarks.

    “The quarks inside these particles behave like electrons inside atoms,” Skwarnicki says. “They can be ‘excited’ and jump into higher energy orbitals. The energy configuration of the quarks gives each particle its unique mass and identity.”

    According to theoretical predictions, the quarks inside could be tightly bound (like three quarks packed inside a single proton) or loosely bound (like two atoms forming a molecule.) By closely examining each particle’s quantum numbers, scientists were able to narrow down the possible structures.

    “The molecular explanation does not fit with the data,” Skwarnicki says. “But I personally would not conclude that these are definitely tightly bound states of four quarks. It could be possible that these are not even particles. The result could show the complex interplays of known particle pairs flippantly changing their identities.”

    Theorists are currently working on models to explain these new results—be it a family of four new particles or bizarre ripple effects from known particles. Either way, this study will help shape our understanding of the subatomic universe.

    “The huge amount of data generated by the LHC is enabling a resurgence in searches for exotic particles and rare physical phenomena,” Britton says. “There’s so many possible things for us to find and I’m happy to be a part of it.”

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Symmetry is a joint Fermilab/SLAC publication.

Compose new post
Next post/Next comment
Previous post/Previous comment
Show/Hide comments
Go to top
Go to login
Show/Hide help
shift + esc
%d bloggers like this: