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 3 added 22 characters in body; deleted 4 characters in body edited Apr 20 '13 at 20:34 innisfree 12.3k33 gold badges3434 silver badges6565 bronze badges Transverse momentum, $$p_T$$$$\vec{p}_T$$, is the momentum of an object transverse to the beam. Transverse energy is defined as $$E_T = \sqrt{m^2+p_T^2}$$ for an object with mass $$m$$ and transverse momentum $$p_T$$. The initial longitudinal momentum in a parton collision is unknown, because the partons that make up a proton share the momentum. We do know, however, that the initial transverse momentum was zero. So we look for missing transverse momentum, defined $$E_T^\textrm{miss} = -\sum_i p_T(i)$$$$E_T^\textrm{miss} = -\sum_i \vec{p}_T(i)$$ for visible particles $$i$$. Finding missing transverse momentum would indicate that new, unaccounted for particle(s) had escaped the detector. Confusingly, $$E_T^\textrm{miss} = -\sum_i p_T(i)$$$$E_T^\textrm{miss} = -\sum_i \vec{p}_T(i)$$ is commonly called missing transverse energy or MET. Missing transverse energy is equivalent to missing transverse momentum only if the missing particle(s) were massless. Also, events in which the products have large transverse momentum are more likely to be genuine, interesting events. Transverse momentum, $$p_T$$, is the momentum of an object transverse to the beam. Transverse energy is defined as $$E_T = \sqrt{m^2+p_T^2}$$ for an object with mass $$m$$ and transverse momentum $$p_T$$. The initial longitudinal momentum in a parton collision is unknown, because the partons that make up a proton share the momentum. We do know, however, that the initial transverse momentum was zero. So we look for missing transverse momentum, defined $$E_T^\textrm{miss} = -\sum_i p_T(i)$$ for visible particles $$i$$. Finding missing transverse momentum would indicate that new, unaccounted for particle(s) had escaped the detector. Confusingly, $$E_T^\textrm{miss} = -\sum_i p_T(i)$$ is commonly called missing transverse energy or MET. Missing transverse energy is equivalent to missing transverse momentum only if the missing particle(s) were massless. Also, events in which the products have large transverse momentum are more likely to be genuine, interesting events. Transverse momentum, $$\vec{p}_T$$, is the momentum of an object transverse to the beam. Transverse energy is defined as $$E_T = \sqrt{m^2+p_T^2}$$ for an object with mass $$m$$ and transverse momentum $$p_T$$. The initial longitudinal momentum in a parton collision is unknown, because the partons that make up a proton share the momentum. We do know, however, that the initial transverse momentum was zero. So we look for missing transverse momentum, defined $$E_T^\textrm{miss} = -\sum_i \vec{p}_T(i)$$ for visible particles $$i$$. Finding missing transverse momentum would indicate that new, unaccounted for particle(s) had escaped the detector. Confusingly, $$E_T^\textrm{miss} = -\sum_i \vec{p}_T(i)$$ is commonly called missing transverse energy or MET. Missing transverse energy is equivalent to missing transverse momentum only if the missing particle(s) were massless. Also, events in which the products have large transverse momentum are more likely to be genuine, interesting events. 2 added 559 characters in body edited Apr 20 '13 at 20:29 innisfree 12.3k33 gold badges3434 silver badges6565 bronze badges ItTransverse momentum, $$p_T$$, is the momentum of an object transverse to the beam. Transverse energy is defined as $$E_T = \sqrt{m^2+p_T^2}$$ for an object with mass $$m$$ and transverse momentum $$p_T$$.  The initial longitudinal momentum in a parton collision is unknown, because the partons that make up a proton share the momentum.   We do know, however, that the initial transverse momentum was zero. So we look for missing transverse momentum, defined $$E_T^\textrm{miss} = -\sum_i p_T(i)$$ for visible particles $$i$$. Finding missing transverse momentum would indicate that new, unaccounted for particle(s) had escaped the detector. Confusingly, $$E_T^\textrm{miss} = -\sum_i p_T(i)$$ is commonly called missing transverse energy or MET. Missing transverse energy is equivalent to missing transverse momentum only if the missing particle(s) were massless. Also, events in which the products have large transverse momentum are more likely to be genuine, interesting events. It is the momentum of an object transverse to the beam. The initial longitudinal momentum in a parton collision is unknown, because the partons that make up a proton share the momentum.   We do know, however, that the initial transverse momentum was zero. So we look for missing transverse momentum. Also, events in which the products have large transverse momentum are more likely to be genuine, interesting events. Transverse momentum, $$p_T$$, is the momentum of an object transverse to the beam. Transverse energy is defined as $$E_T = \sqrt{m^2+p_T^2}$$ for an object with mass $$m$$ and transverse momentum $$p_T$$.  The initial longitudinal momentum in a parton collision is unknown, because the partons that make up a proton share the momentum. We do know, however, that the initial transverse momentum was zero. So we look for missing transverse momentum, defined $$E_T^\textrm{miss} = -\sum_i p_T(i)$$ for visible particles $$i$$. Finding missing transverse momentum would indicate that new, unaccounted for particle(s) had escaped the detector. Confusingly, $$E_T^\textrm{miss} = -\sum_i p_T(i)$$ is commonly called missing transverse energy or MET. Missing transverse energy is equivalent to missing transverse momentum only if the missing particle(s) were massless. Also, events in which the products have large transverse momentum are more likely to be genuine, interesting events. 1 answered Apr 20 '13 at 18:03 innisfree 12.3k33 gold badges3434 silver badges6565 bronze badges It is the momentum of an object transverse to the beam. The initial longitudinal momentum in a parton collision is unknown, because the partons that make up a proton share the momentum. We do know, however, that the initial transverse momentum was zero. So we look for missing transverse momentum. Also, events in which the products have large transverse momentum are more likely to be genuine, interesting events.