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Distinguishing 'Higgs' spin hypotheses using $\gamma \gamma$ and $W W^*$ decays
The new particle X recently discovered by the ATLAS and CMS Collaborations in searches for the Higgs boson has been observed to decay into gamma gamma, ZZ* and WW*, but its spin and parity, J^P, remain a mystery, with J^P = 0^+ and 2^+ being open possibilities. We use PYTHIA and Delphes to simulate...
Autores principales: | , , , , |
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Lenguaje: | eng |
Publicado: |
2012
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Materias: | |
Acceso en línea: | https://dx.doi.org/10.1140/epjc/s10052-013-2488-5 http://cds.cern.ch/record/1485853 |
_version_ | 1780926095048048640 |
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author | Ellis, John Fok, Ricky Hwang, Dae Sung Sanz, Veronica You, Tevong |
author_facet | Ellis, John Fok, Ricky Hwang, Dae Sung Sanz, Veronica You, Tevong |
author_sort | Ellis, John |
collection | CERN |
description | The new particle X recently discovered by the ATLAS and CMS Collaborations in searches for the Higgs boson has been observed to decay into gamma gamma, ZZ* and WW*, but its spin and parity, J^P, remain a mystery, with J^P = 0^+ and 2^+ being open possibilities. We use PYTHIA and Delphes to simulate an analysis of the angular distribution of gg to X to gamma gamma decays in a full 2012 data set, including realistic background levels. We show that this angular distribution should provide strong discrimination between the possibilities of spin zero and spin two with graviton-like couplings: ~ 3 sigma if a conservative symmetric interpretation of the log-likelihood ratio (LLR) test statistic is used, and ~ 6 sigma if a less conservative asymmetric interpretation is used. The WW and ZZ couplings of the Standard Model Higgs boson and of a 2^+ particle with graviton-like couplings are both expected to exhibit custodial symmetry. We simulate the present ATLAS and CMS search strategies for X to WW* using PYTHIA and Delphes, and show that their efficiencies in the case of a spin-two particle with graviton-like couplings are a factor ~ 1.9 smaller than in the spin-zero case. On the other hand, the ratio of X_{2^+} to WW* and ZZ* branching ratios is larger than that in the 0^+ case by a factor ~ 1.3. We find that the current ATLAS and CMS results for X to WW* and X to ZZ* decays are compatible with custodial symmetry under both the spin-zero and -two hypotheses, and that the data expected to become available during 2012 are unlikely to discriminate significantly between these possibilities. |
id | cern-1485853 |
institution | Organización Europea para la Investigación Nuclear |
language | eng |
publishDate | 2012 |
record_format | invenio |
spelling | cern-14858532019-09-30T06:29:59Zdoi:10.1140/epjc/s10052-013-2488-5http://cds.cern.ch/record/1485853engEllis, JohnFok, RickyHwang, Dae SungSanz, VeronicaYou, TevongDistinguishing 'Higgs' spin hypotheses using $\gamma \gamma$ and $W W^*$ decaysParticle Physics - PhenomenologyThe new particle X recently discovered by the ATLAS and CMS Collaborations in searches for the Higgs boson has been observed to decay into gamma gamma, ZZ* and WW*, but its spin and parity, J^P, remain a mystery, with J^P = 0^+ and 2^+ being open possibilities. We use PYTHIA and Delphes to simulate an analysis of the angular distribution of gg to X to gamma gamma decays in a full 2012 data set, including realistic background levels. We show that this angular distribution should provide strong discrimination between the possibilities of spin zero and spin two with graviton-like couplings: ~ 3 sigma if a conservative symmetric interpretation of the log-likelihood ratio (LLR) test statistic is used, and ~ 6 sigma if a less conservative asymmetric interpretation is used. The WW and ZZ couplings of the Standard Model Higgs boson and of a 2^+ particle with graviton-like couplings are both expected to exhibit custodial symmetry. We simulate the present ATLAS and CMS search strategies for X to WW* using PYTHIA and Delphes, and show that their efficiencies in the case of a spin-two particle with graviton-like couplings are a factor ~ 1.9 smaller than in the spin-zero case. On the other hand, the ratio of X_{2^+} to WW* and ZZ* branching ratios is larger than that in the 0^+ case by a factor ~ 1.3. We find that the current ATLAS and CMS results for X to WW* and X to ZZ* decays are compatible with custodial symmetry under both the spin-zero and -two hypotheses, and that the data expected to become available during 2012 are unlikely to discriminate significantly between these possibilities.arXiv:1210.5229KCL-PH-TH-2012-44LCTS-2012-29CERN-PH-TH-2012-268oai:cds.cern.ch:14858532012-10-19 |
spellingShingle | Particle Physics - Phenomenology Ellis, John Fok, Ricky Hwang, Dae Sung Sanz, Veronica You, Tevong Distinguishing 'Higgs' spin hypotheses using $\gamma \gamma$ and $W W^*$ decays |
title | Distinguishing 'Higgs' spin hypotheses using $\gamma \gamma$ and $W W^*$ decays |
title_full | Distinguishing 'Higgs' spin hypotheses using $\gamma \gamma$ and $W W^*$ decays |
title_fullStr | Distinguishing 'Higgs' spin hypotheses using $\gamma \gamma$ and $W W^*$ decays |
title_full_unstemmed | Distinguishing 'Higgs' spin hypotheses using $\gamma \gamma$ and $W W^*$ decays |
title_short | Distinguishing 'Higgs' spin hypotheses using $\gamma \gamma$ and $W W^*$ decays |
title_sort | distinguishing 'higgs' spin hypotheses using $\gamma \gamma$ and $w w^*$ decays |
topic | Particle Physics - Phenomenology |
url | https://dx.doi.org/10.1140/epjc/s10052-013-2488-5 http://cds.cern.ch/record/1485853 |
work_keys_str_mv | AT ellisjohn distinguishinghiggsspinhypothesesusinggammagammaandwwdecays AT fokricky distinguishinghiggsspinhypothesesusinggammagammaandwwdecays AT hwangdaesung distinguishinghiggsspinhypothesesusinggammagammaandwwdecays AT sanzveronica distinguishinghiggsspinhypothesesusinggammagammaandwwdecays AT youtevong distinguishinghiggsspinhypothesesusinggammagammaandwwdecays |