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Could proton-proton Collisions in the LHC produce Gravitons?

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marked as duplicate by Cosmas Zachos, John Rennie, Yashas, AccidentalFourierTransform, knzhou Jun 3 '17 at 18:41

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Models with large extra dimensions, like the ones proposed by Arkani-Hamed, Dimopoulos, and Dvali (ADD) on one hand, and Randall and Sundrum (RS) on the other hand, do predict gravitons within the reach of LHC. There are plenty of theoretical and experimental efforts directed into this search. For a recent review on ADD, see [1]. Even if you are not a professional, the introduction may give you an idea!

In the ADD model, the gravitons do not decay and therefore the signal would be missing energy, specifically $pp \to \text{jet} + \text{(missing energy)}$. There is a Standard Model (SM) background, $pp \to \text{jet} + Z$ where the $Z$ decays into a pair of neutrinos.

In the RS model, the gravitons decay into pairs of Standard Model particle. According to the Particle Data Group review, the most stringent limits come from decays into dilepton and diphoton. Here too there is a Standard Model background, the so-called Drell-Yan process $pp \to \text{jet} + Z^0/\gamma$ and then $Z/\gamma \to l^+ l^-$ for the dilepton.

[1] https://arxiv.org/abs/1005.1805

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  • $\begingroup$ So if the LHC does indeed produce Gravitons it then has the problem of detecting them. I assume this means using some Graviton decay channel. $\endgroup$ – Ken Abbott Jun 3 '17 at 12:18
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    $\begingroup$ No actually, the graviton would appear as missing energy. More precisely, pp $\to$ jet + missing energy. But there is a Standard Model background: pp $\to$ Z + jet, where Z decays to two neutrinos. So the game is then to put clever cuts on the jet kinematics to exclude as much of the background as possible. $\endgroup$ – user154997 Jun 3 '17 at 15:11
  • $\begingroup$ But could the graviton decay g -> e+, e- and thus mess up the missing energy method. $\endgroup$ – Ken Abbott Jun 3 '17 at 16:24
  • $\begingroup$ I was wrong actually! Best to update my answer… $\endgroup$ – user154997 Jun 3 '17 at 17:41

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