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Z' at the LHC: interference and finite width effects in Drell-Yan

Z' at the LHC: interference and finite width effects in Drell-Yan
Z' at the LHC: interference and finite width effects in Drell-Yan
The interference effects between an extra neutral spin-1 Z'-boson and the Standard Model background in the Drell-Yan channel at the LHC are studied in detail. The final state with two oppositely charged leptons is considered. The interference contribution to the new physics signal, currently not fully taken into account by experimental collaborations in Z'-searches and in the interpretation of the results, can be substantial. It may affect limits or discovery prospects of Z' at the LHC. As the Z'-boson interference is model-dependent, a proper treatment would a priori require a dedicated experimental analysis for each particular model. Doing so could potentially improve the sensitivity to new physics, but would require significantly more experimental effort. At the same time, it is shown that one can define an invariant mass window, valid for a wide range of models, for which the contribution of the model-dependent interference to the Beyond the Standard Model signal is reduced to O(10%), comparable to the level of the combined uncertainty from parton densities and higher order corrections. This quasi-model-independent "magic cut" does not scale with the mass of the Z'-boson and is approximately constant over a large range of masses. Such control of the interference effects relies on not-too-small branching ratios of Z' to leptons (typically of at least a few percent) which can be suppressed, however, by additional new decay channels of the Z'; a small width-to-mass ratio alone does not guarantee the interference to be small over an arbitrary kinematic range. Under the general assumption that these new decay channels of Z' are not dominant, one can perform quasi-model-independent analyses, preserving the current scheme used by the experimental collaborations for the Z'-boson search using the suggested invariant mass window cut.
hep-ph, hep-ex
1029-8479
Accomando, Elena
8ebc75d7-bd92-4f70-a974-7bc15ebf088f
Becciolini, Diego
f25f7755-ebb8-48e8-a40a-a962a1c90548
Belyaev, Alexander
6bdb9638-5ff9-4b65-a8f2-34bae3ac34b3
Moretti, Stefano
b57cf0f0-4bc3-4e02-96e3-071255366614
Shepherd-Themistocleous, Claire
a29b4897-1b61-4774-8df7-0f507d905d81
Accomando, Elena
8ebc75d7-bd92-4f70-a974-7bc15ebf088f
Becciolini, Diego
f25f7755-ebb8-48e8-a40a-a962a1c90548
Belyaev, Alexander
6bdb9638-5ff9-4b65-a8f2-34bae3ac34b3
Moretti, Stefano
b57cf0f0-4bc3-4e02-96e3-071255366614
Shepherd-Themistocleous, Claire
a29b4897-1b61-4774-8df7-0f507d905d81

Accomando, Elena, Becciolini, Diego, Belyaev, Alexander, Moretti, Stefano and Shepherd-Themistocleous, Claire (2013) Z' at the LHC: interference and finite width effects in Drell-Yan. Journal of High Energy Physics, 2013 (10), [153]. (doi:10.1007/JHEP10(2013)153).

Record type: Article

Abstract

The interference effects between an extra neutral spin-1 Z'-boson and the Standard Model background in the Drell-Yan channel at the LHC are studied in detail. The final state with two oppositely charged leptons is considered. The interference contribution to the new physics signal, currently not fully taken into account by experimental collaborations in Z'-searches and in the interpretation of the results, can be substantial. It may affect limits or discovery prospects of Z' at the LHC. As the Z'-boson interference is model-dependent, a proper treatment would a priori require a dedicated experimental analysis for each particular model. Doing so could potentially improve the sensitivity to new physics, but would require significantly more experimental effort. At the same time, it is shown that one can define an invariant mass window, valid for a wide range of models, for which the contribution of the model-dependent interference to the Beyond the Standard Model signal is reduced to O(10%), comparable to the level of the combined uncertainty from parton densities and higher order corrections. This quasi-model-independent "magic cut" does not scale with the mass of the Z'-boson and is approximately constant over a large range of masses. Such control of the interference effects relies on not-too-small branching ratios of Z' to leptons (typically of at least a few percent) which can be suppressed, however, by additional new decay channels of the Z'; a small width-to-mass ratio alone does not guarantee the interference to be small over an arbitrary kinematic range. Under the general assumption that these new decay channels of Z' are not dominant, one can perform quasi-model-independent analyses, preserving the current scheme used by the experimental collaborations for the Z'-boson search using the suggested invariant mass window cut.

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More information

Accepted/In Press date: 25 September 2013
Published date: 23 October 2013
Additional Information: arXiv version is 16 pages, 4 figures, 1 table; version matching JHEP publication
Keywords: hep-ph, hep-ex
Organisations: Physics & Astronomy

Identifiers

Local EPrints ID: 356657
URI: http://eprints.soton.ac.uk/id/eprint/356657
ISSN: 1029-8479
PURE UUID: ff6c807b-58d7-47e3-b687-6ae2ffdab9e6
ORCID for Alexander Belyaev: ORCID iD orcid.org/0000-0002-1733-4408

Catalogue record

Date deposited: 17 Sep 2013 10:46
Last modified: 09 Nov 2021 03:16

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Contributors

Author: Elena Accomando
Author: Diego Becciolini
Author: Stefano Moretti
Author: Claire Shepherd-Themistocleous

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