Radiative distortion of kinematic edges in cascade decays

Beneke, Μ.; Jenniches, Laura; Mück, Alexander; Ubiali, Maria

doi:10.1016/j.physletb.2017.04.018

Cited by 3 publications

(2 citation statements)

References 11 publications

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“…One should be mindful of the fact that there are other factors which also affect the shape of the invariant mass distribution dN/dm. On the theoretical side, there could be spin correlations [20][21][22][23], interference [24,25] and higher order effects [26,27]. On the experimental side, the cuts and the detector resolution will also play a role in this measurement.…”

Section: Introduction /mentioning

confidence: 99%

How to prove that a ET excess at the LHC is not due to dark matter

Kim

Matchev

2018

Phys. Rev. D

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If the LHC is able to produce dark matter particles, they would appear at the end of cascade decay chains, manifesting themselves as missing transverse energy. However, such "dark matter candidates" may decay invisibly later on. We propose to test for this possibility by studying the effect of particle widths on the observable invariant mass distributions of the visible particles seen in the detector. We consider the simplest non-trivial case of a two-step two-body cascade decay and derive analytically the shapes of the invariant mass distributions, for generic values of the widths of the new particles. We demonstrate that the resulting distortion in the shape of the invariant mass distribution can be significant enough to measure the width of the dark matter "candidate", ruling it out as the source of the cosmological dark matter.PACS numbers: 95.35.+d, 13.85.Qk Introduction. / E T events at the Large Hadron Collider (LHC) at CERN are motivated by the dark matter problem -the dark matter particles are stable and weakly interacting, and, once produced in the LHC collisions, will escape without leaving a trace inside the detector. This will lead to an imbalance in the transverse momentum of the event, known as "missing transverse momentum" / P T .[29] However, the reverse statement is not so obvious -if we observe an excess of / E T events at the LHC, how can one be sure that what we are seeing is indeed the cosmological dark matter?The question of proving that a / E T signal observed at the LHC is indeed due to dark matter, has attracted a lot of attention in the past [1-8]. The basic idea was to test whether the newly discovered weakly interacting massive particle (WIMP) was consistent with being a thermal relic or not. The general approach was to assume a specific model, most often some version of low-energy supersymmetry, and then attempt to measure all relevant model parameters affecting the thermal relic density calculation. Unfortunately, such an approach is modeldependent; applies only to thermal relics (for alternative non-thermal scenarios, see [9,10]); requires full understanding of the early cosmology; and typically demands a large number of additional measurements, possibly at future (or futuristic) facilities.Given that proving the discovery of dark matter at the LHC is such a difficult task, perhaps one should focus on the opposite question -how to disprove that the newly found invisible particle is the cosmological dark matter. One possibility is to perform a precise measurement of its mass, and if the mass is consistent with zero, it may just be one of the Standard Model (SM) neutrinos instead of a brand new particle [11]. However, this logic is not ironclad either -there exist examples where the dark matter particles are very light [12,13] and cannot be ruled out just on the basis of their small mass.A much more direct approach would be to test whether the particle which is the source of the / E T is indeed stable -after all, we only know that it did not decay inside the detector. If its lifet...

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Section: Introduction /mentioning

confidence: 99%

How to prove that a ET excess at the LHC is not due to dark matter

Kim

Matchev

2018

Phys. Rev. D

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“…The envelope of m T 2 (m trial ) curves exhibits a kink at m trial = m χ , where m T 2 = m g. Measuring the kink determines both masses (for the effect of radiative corrections see [20]). For two body decays, e.g., for squark decays, q → qχ, the kinks in the distributions appear only once initial state radiation is included [7].…”

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confidence: 99%

End-point resummation in squark decays

Kim,

Lee

et al. 2018

Preprint

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We study soft and collinear gluon emission in squark decays to quark-neutralino pair, at next-tonext-to-leading logarithmic (NNLL) accuracy in the end-point region, using Soft Collinear Effective Theory (SCET), and at next-to-leading (NLO) fixed order in the rest of the phase space. As a phenomenological case study we discuss the impact of radiative corrections on the simultaneous measurements of squark and neutralino masses at a linear e + e − collider based on √ s = 3 TeV Compact Linear Collider (CLIC). Since the majority of mass measurement techniques are based on edges in kinematic distributions, and these change appreciably when there is additional QCD radiation in the final state, the knowledge of higher-order QCD effects is required for precise mass determinations.

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Endpoint resummation in squark decays

Kim

Lee³

et al. 2020

Phys. Rev. D

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Radiative distortion of kinematic edges in cascade decays

Cited by 3 publications

References 11 publications

How to prove that a ET excess at the LHC is not due to dark matter

How to prove that a ET excess at the LHC is not due to dark matter

End-point resummation in squark decays

Endpoint resummation in squark decays

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