Nov 19, 2021 16:00 PM

Speaker: Cristián Peña, Fermilab

" data-hasqtip="0" aria-describedby="qtip-0" >VIRTUAL meeting ONLY: Theoretical Physics Seminar: Recent long Lived particle searches in ~ CMS
Nov 19, 2021 19:30 PM

Speaker: Joe Roman, college of VermontTickets:

" data-hasqtip="0" aria-describedby="qtip-0" >Virtual art & lecture Series: Eat the Invaders



Protons and antiprotons are composite objects, formed from a constantly transforming mixture of quarks and gluons (partons). In a small fraction of collisions there deserve to be more than one parton-parton interaction. Measure up the rate of such dual interactions provides important information about the framework of the proton.

You are watching: When a proton and an antiproton collide, they

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What happens as soon as protons and also antiprotons collide? to answer this question, we very first need to consider what we typical by a fragment collision. The proton is no fundamental: It has an evolving mixture the quarks, antiquarks and gluons. These quarks and gluons are jointly called partons and are held together by the QCD interaction, favor marbles in a bag. While the marble an allegory is failure in plenty of ways, like many real-world imaginings of quantum behavior, it provides a valuable analogy to take into consideration the various possible outcomes of fragment collisions, for this reason let’s go v it.

The most usual outcome that a proton-antiproton collision is that the two hadrons just break personally — the two bags that marbles rest — weakly scattering the inner quarks and also gluons. This is dubbed a “soft” interaction. The collisions that we room usually interested in room those in which a parton native the proton interacts directly with a parton from the antiproton in a “hard” scattering process that deserve to produce brand-new particles such together Higgs, W and Z bosons and also other quarks. In ours analogy, this would be two marbles, one from each bag, hitting each other and also breaking apart.

Occasionally, however, there can be an ext than one hard interaction per collision: In other words, two different pairs that marbles smash together or two pairs the partons interact. This so-called double-parton interaction are much rarer than the usual solitary parton case, and their ubiquity provides important information top top the spatial distribution and transverse momentum of the quarks and gluons inside the proton. This week the DZero participation will relax a brand-new publication, measuring the rate of double-parton interactions using events with three quarks and also a photon in the last state.

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The measurement uses a clever feature of the data to enhance the precision: sometimes two single-parton interaction can happen in different proton-antiproton collisions. In our analogy, two bags that marbles collide at suggest A, and also another two collide at suggest B. By to compare the number of selected events with one versus two separate collision points, the ratio of single- come double-parton interactions have the right to be extracted v minimal dependency on the details the the detector efficiency. Furthermore, particular characteristics of the double-parton events enable them come be identified by their experimental signature and also discriminated native the main backgrounds.

The final results are expressed in terms of an reliable cross section (the transverse area in the (anti)proton populated by the interacting partons) and also are the most an exact ever made. In addition, because that the first time the measure up is also performed separately for occasions where among the partons was a heavy quark (beauty or charm). Interestingly, the measurement indicates that the probability the a double-parton interaction is the exact same regardless of the flavor of the early parton: Unlike many of us, parton interaction don’t seem come be affected by charm and also beauty!

Mark Williams

These DZero members all made far-reaching contributions come this publication.
The DZero collaboration continues to thrive much more than two years after the last Tevatron collisions took place. This main sees the coming together of researchers from about the human being at Fermilab for the winter DZero participation meeting. The aim is to push forward a variety of dimensions toward publication, with much more than 20 different analyses being presented because that discussion.