![]() When the world began, the human race lived as nothing more than cattle. ![]() Only if they stand together will they discover secret of those that are the puppets and the ones pulling the strings. When a friend vanishes, he unknowingly joins the search for those who are hiding in the shadows and the fight that is building between them. Jimmy has his own problems as he fights to reconcile his past with his present. When a new and powerful enemy emerges, the Walkers search out their trusted friends to help them discover the truth behind a terrible weapon that threatens their very existence. When a friend vanishes, he unknowingly joins the search for those who are hiding in the shadow The Gathering Storm… We welcome Boris Tuchming (center, CEA/Irfu/SPP, Saclay, France) as he joins Robert Hirosky (right, University of Virginia) in this crucially important task.The Gathering Storm… When a new and powerful enemy emerges, the Walkers search out their trusted friends to help them discover the truth behind a terrible weapon that threatens their very existence. Rick has taken on the new responsibility of vice provost for research at Indiana University. ![]() The DZero collaboration thanks Rick Van Kooten (left) for his service in ensuring the highest quality of physics output in his role as physics convener. Bottom row, from left: Ivan Heredia (CINVESTAV, Mexico) and Daria Ziemianska (Indiana University). Top row, from left: Avdhesh Chandra (Rice University), Eduard de la Cruz-Burelo, Jose Andres Garcia-Gonzalez (both of CINVESTAV, Mexico). ![]() These scientists are the primary analysts for this measurement. It turns out that the data match the simple string-pulling prediction quite well! The interesting thing to measure is how often the Λ b is produced going in the direction that the QCD string would have pulled it (that is, in the initial proton direction) versus how often it is produced going in the opposite (antiproton) direction. From this scenario, it is straightforward to estimate how much the string’s pull would change the direction of the motion of the bottom quark and hence the direction of the Λ b.ĭZero has recently measured the directions of Λ b particles produced at the Tevatron. The other end of the string is tied to the fragments of the proton after the collision they travel mostly in the same direction as the incoming proton, and so they would drag the bottom quark along in that same direction. He realized that QCD strings would pull on the post-collision bottom quark in the direction of the incoming proton. In particular, he looked at the case where the bottom quark joins with an up and a down quark to make a particle known as the Λ b (pronounced “lambda sub b”) in proton-antiproton collisions. In a paper published last summer, Jonathan Rosner of the University of Chicago pondered how these strings - strings governed by quantum chromodynamics, or QCD - might pull on bottom quark-antiquark pairs. The idea behind string fragmentation is that when quarks pull on each other, it is as if there is a string tying them together, with a force that increases with their separation. The energy of the force field between the quarks is concentrated in a long thin tube or string-shaped volume that stretches from one quark to the other. Quarks pull on each other as a result of the strong nuclear force. Rather, today’s result involves string fragmentation, an approximate description of the strong nuclear force. Today’s article involves strings and theory, but not string theory. The other ends of the strings are connected to the outgoing fragments of the colliding proton and antiproton (not shown). Thinking of our two goats as a bottom quark-antiquark pair produced in a Tevatron collision, the strong nuclear force strings will pull them in certain specific directions. The nature of the strong nuclear force is such that the energy of its field is concentrated in long thin tubes, or strings, that pull on quarks.
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