MSGID: 1:317/3 643f6e64   
   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Teasing strange matter from the ordinary    
      
     Date:   
         April 18, 2023   
     Source:   
         DOE/Thomas Jefferson National Accelerator Facility   
     Summary:   
         In a unique analysis of experimental data, nuclear physicists   
         have made observations of how lambda particles, so-called 'strange   
         matter,' are produced by a specific process called semi-inclusive   
         deep inelastic scattering (SIDIS). What's more, these data hint   
         that the building blocks of protons, quarks and gluons, are capable   
         of marching through the atomic nucleus in pairs called diquarks,   
         at least part of the time.   
      
      
         Facebook Twitter Pinterest LinkedIN Email   
   FULL STORY   
   ==========================================================================   
   In a unique analysis of experimental data, nuclear physicists have made   
   the first-ever observations of how lambda particles, so-called "strange   
   matter," are produced by a specific process called semi-inclusive deep   
   inelastic scattering (SIDIS). What's more, these data hint that the   
   building blocks of protons, quarks and gluons, are capable of marching   
   through the atomic nucleus in pairs called diquarks, at least part   
   of the time. These results come from an experiment conducted at the   
   U.S. Department of Energy's Thomas Jefferson National Accelerator   
   Facility.   
      
      
   ==========================================================================   
   It's a result that has been decades in the making. The dataset was   
   originally collected in 2004. Lamiaa El Fassi, now an associate professor   
   of physics at Mississippi State University and principal investigator   
   of the work, first analyzed these data during her thesis project to earn   
   her graduate degree on a different topic.   
      
   Nearly a decade after completing her initial research with these data,   
   El Fassi revisited the dataset and led her group through a careful   
   analysis to yield these unprecedented measurements. The dataset comes   
   from experiments in Jefferson Lab's Continuous Electron Beam Accelerator   
   Facility (CEBAF), a DOE user facility. In the experiment, nuclear   
   physicists tracked what happened when electrons from CEBAF scatter off   
   the target nucleus and probe the confined quarks inside protons and   
   neutrons. The results were recently published in Physical Review Letters.   
      
   "These studies help build a story, analogous to a motion picture,   
   of how the struck quark turns into hadrons. In a new paper, we report   
   first-ever observations of such a study for the lambda baryon in the   
   forward and backward fragmentation regions," El Fassi said.   
      
   In like a lambda, out like a pion Like the more familiar protons and   
   neutrons, each lambda is made up of three quarks.   
      
   Unlike protons and neutrons, which only contain a mixture of up and   
   down quarks, lambdas contain one up quark, one down quark and one   
   strange quark.   
      
   Physicists have dubbed matter that contains strange quarks "strange   
   matter."  In this work, El Fassi and her colleagues studied how these   
   particles of strange matter form from collisions of ordinary matter. To   
   do so, they shot CEBAF's electron beam at different targets, including   
   carbon, iron, and lead.   
      
   When a high-energy electron from CEBAF reaches one of these targets,   
   it breaks apart a proton or neutron inside one of the target's nuclei.   
      
   "Because the proton or neutron is totally broken apart, there is little   
   doubt that the electron interacts with the quark inside," El Fassi said.   
      
   After the electron interacts with a quark or quarks via an exchanged   
   virtual photon, the "struck" quark(s) begins moving as a free particle   
   in the medium, typically joining up with other quark(s) it encounters to   
   form a new composite particle as they propagate through the nucleus. And   
   some of the time, this composite particle will be a lambda.   
      
   But the lambda is short-lived -- after formation, it will swiftly decay   
   into two other particles: a pion and either a proton or neutron. To   
   measure different properties of these briefly created lambda particles,   
   physicists must detect its two daughter particles, as well as the beam   
   electron that scattered off the target nucleus.   
      
   The experiment that collected this data, EG2, used the CEBAF Large   
   Acceptance Spectrometer (CLAS) detector in Jefferson Lab's Experimental   
   Hall B. These recently published results, "First Measurement of   
   ? Electroproduction off Nuclei in the Current and Target Fragmentation   
   Regions," are part of the CLAS collaboration, which involves almost 200   
   physicists worldwide.   
      
   SIDIS This work is the first to measure the lambda using this process,   
   which is known as semi-inclusive deep inelastic scattering, in the   
   forward and backward fragmentation regions. It's more difficult to use   
   this method to study lambda particles, because the particle decays so   
   quickly, it can't be measured directly.   
      
   "This class of measurement has only been performed on protons before,   
   and on lighter, more stable particles," said coauthor William Brooks,   
   professor of physics at Federico Santa Mari'a Technical University and   
   co-spokesperson of the EG2 experiment.   
      
   The analysis was so challenging, it took several years for El Fassi   
   and her group to re-analyze the data and extract these results. It was   
   her thesis advisor, Kawtar Hafidi, who encouraged her to pursue the   
   investigation of the lambda from these datasets.   
      
   "I would like to commend Lamiaa's hard work and perseverance in dedicating   
   years of her career working on this," said Hafidi, associate laboratory   
   director for physical sciences and engineering at Argonne National Lab and   
   co- spokesperson of the EG2 experiment. "Without her, this work would not   
   have seen fruition."  "It hasn't been easy," El Fassi said. "It's a long   
   and time-consuming process, but it was worth the effort. When you spend   
   so many years working on something, it feels good to see it published."   
   El Fassi began this lambda analysis when she herself was a postdoc, a   
   couple of years prior to becoming an assistant professor at Mississippi   
   State University.   
      
   Along the way, several of her own postdocs at Mississippi State have   
   helped extract these results, including coauthor Taya Chetry.   
      
   "I'm very happy and motivated to see this work being published," said   
   Chetry, who is now a postdoctoral researcher at Florida International   
   University.   
      
   Two for one A notable finding from this intensive analysis changes the way   
   physicists understand how lambdas form in the wake of particle collisions.   
      
   In similar studies that have used semi-inclusive deep inelastic scattering   
   to study other particles, the particles of interest usually form after   
   a single quark was "struck" by the virtual photon exchanged between the   
   electron beam and the target nucleus. But the signal left by lambda in   
   the CLAS detector suggests a more packaged deal.   
      
   The authors' analysis showed that when forming a lambda, the virtual   
   photonhas been absorbed part of the time by a pair of quarks, known as   
   a diquark, instead of just one. After being "struck," this diquark went   
   on to find a strange quark and forms a lambda.   
      
   "This quark pairing suggests a different mechanism of production and   
   interaction than the case of the single quark interaction," Hafidi said.   
      
   A better understanding of how different particles form helps physicists   
   in their effort to decipher the strong interaction, the fundamental   
   force that holds these quark-containing particles together. The dynamics   
   of this interaction are very complicated, and so is the theory used to   
   describe it: quantum chromodynamics (QCD).   
      
   Comparing measurements to models of QCD's predictions allows physicists   
   to test this theory. Because the diquark finding differs from the model's   
   current predictions, it suggests something about the model is off.   
      
   "There is an unknown ingredient that we don't understand. This is   
   extremely surprising, since the existing theory can describe essentially   
   all other observations, but not this one," Brooks said. "That means there   
   is something new to learn, and at the moment, we have no clue what it   
   could be."  To find out, they'll need even more measurements.   
      
   Data for EG2 were collected with 5.014 GeV (billion electron-volt)   
   electron beams in the CEBAF's 6 GeV era. Future experiments will use   
   electron beams from the updated CEBAF, which now extend up to 11 GeV   
   for Experimental Hall B, as well as an updated CLAS detector known as   
   CLAS12, to continue studying the formation of a variety of particles,   
   including lambdas, with higher-energy electrons.   
      
   The upcoming Electron-Ion Collider (EIC) at DOE's Brookhaven National   
   Laboratory will also provide a new opportunity to continue studying   
   this strange matter and quark pairing structure of the nucleon with   
   greater precision.   
      
   "These results lay the groundwork for upcoming studies at the upcoming   
   CLAS12 and the planned EIC experiments, where one can investigate the   
   diquark scattering in greater detail," Chetry said.   
      
   El Fassi is also a co-spokesperson for CLAS12 measurements of quark   
   propagation and hadron formation. When data from the new experiments is   
   finally ready, physicists will compare it to QCD predictions to further   
   refine this theory.   
      
   "Any new measurement that will give novel information toward understanding   
   the dynamics of strong interactions is very important," she said.   
      
       * RELATED_TOPICS   
             o Matter_&_Energy   
                   # Quantum_Physics # Physics # Spintronics #   
                   Inorganic_Chemistry # Materials_Science #   
                   Consumer_Electronics # Graphene # Nature_of_Water   
       * RELATED_TERMS   
             o Subatomic_particle o Quark o Particle_physics o   
             Nuclear_reaction o Nuclear_fission o Scientific_method o Atom   
             o Radioactive_decay   
      
   ==========================================================================   
   Story Source: Materials provided by   
   DOE/Thomas_Jefferson_National_Accelerator_Facility.   
      
   Original written by Chris Patrick. Note: Content may be edited for style   
   and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. T. Chetry, L. El Fassi, W. K. Brooks, R. Dupre', A. El   
      Alaoui, K.   
      
         Hafidi, P. Achenbach, K. P. Adhikari, Z. Akbar, W. R.   
      
         Armstrong, M. Arratia, H. Atac, H. Avakian, L. Baashen, N. A.   
      
         Baltzell, L. Barion, M. Bashkanov, M. Battaglieri, I. Bedlinskiy, B.   
      
         Benkel, F. Benmokhtar, A. Bianconi, A. S. Biselli, M. Bondi,   
         W. A. Booth, F. Bossu`, S. Boiarinov, K.-Th. Brinkmann,   
         W. J. Briscoe, D. Bulumulla, V. D. Burkert,   
         D. S.   
      
         Carman, J. C. Carvajal, A. Celentano, P. Chatagnon,   
         V. Chesnokov, G. Ciullo, P. L. Cole, M. Contalbrigo,   
         G. Costantini, A. D'Angelo, N. Dashyan, R. De Vita, M. Defurne,   
         A. Deur, S. Diehl, C. Djalali, H.   
      
         Egiyan, L. Elouadrhiri, P. Eugenio, S. Fegan, A. Filippi,   
         G. Gavalian, Y.   
      
         Ghandilyan, G. P. Gilfoyle, D. I. Glazier,   
         A. A.   
      
         Golubenko, G. Gosta, R. W. Gothe, K. A. Griffioen, M.   
      
         Guidal, L. Guo, H. Hakobyan, M. Hattawy, T. B. Hayward,   
         D. Heddle, A. Hobart, M. Holtrop, Y. Ilieva, D. G. Ireland,   
         E. L.   
      
         Isupov, D. Jenkins, H. S. Jo, M. L. Kabir,   
         A. Khanal, M.   
      
         Khandaker, A. Kim, W. Kim, F. J. Klein, A. Kripko,   
         V. Kubarovsky, V. Lagerquist, L. Lanza, M. Leali, S. Lee, P. Lenisa,   
         X. Li, K.   
      
         Livingston, I. J. D. MacGregor, D. Marchand,   
         V. Mascagna, B. McKinnon, C. McLauchlin, Z. E. Meziani,   
         S. Migliorati, T.   
      
         Mineeva, M. Mirazita, V. Mokeev, C. Munoz Camacho,   
         P. Nadel-Turonski, K.   
      
         Neupane, S. Niccolai, M. Nicol, G. Niculescu, M. Osipenko,   
         A. I.   
      
         Ostrovidov, P. Pandey, M. Paolone, L. L. Pappalardo, R.   
      
         Paremuzyan, E. Pasyuk, S. J. Paul, W. Phelps, N. Pilleux, M.   
      
         Pokhrel, J. Poudel, J. W. Price, Y. Prok, B. A. Raue,   
         T.   
      
         Reed, J. Richards, M. Ripani, J. Ritman, G. Rosner, F. Sabatie', C.   
      
         Salgado, S. Schadmand, A. Schmidt, R. A. Schumacher,   
         Y. G.   
      
         Sharabian, E. V. Shirokov, U. Shrestha, P. Simmerling,   
         D. Sokhan, N. Sparveris, S. Stepanyan, I. I. Strakovsky,   
         S. Strauch, J. A. Tan, N. Trotta, R. Tyson, M. Ungaro,   
         S. Vallarino, L.   
      
         Venturelli, H. Voskanyan, E. Voutier, X. Wei,   
         L. B. Weinstein, R.   
      
         Williams, R. Wishart, M. H. Wood, M. Yurov,   
         N. Zachariou, Z. W. Zhao, M. Zurek. First Measurement   
         of L Electroproduction off Nuclei in the Current and Target   
         Fragmentation Regions. Physical Review Letters, 2023; 130 (14)   
         DOI: 10.1103/PhysRevLett.130.142301   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/04/230418101434.htm   
      
   --- up 1 year, 7 weeks, 1 day, 10 hours, 50 minutes   
    * Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (1:317/3)   
   SEEN-BY: 15/0 106/201 114/705 123/120 153/7715 218/700 226/30 227/114   
   SEEN-BY: 229/110 112 113 307 317 400 426 428 470 664 700 292/854 298/25   
   SEEN-BY: 305/3 317/3 320/219 396/45   
   PATH: 317/3 229/426