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Update on hidden valley searches in Higgs decays

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2015-10-27

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Hidden Valley

2015-10-27

arXiv:hep-ph/0604261

Additional gauge sector Long lived particles weakly

coupled to SM particles HV particles electrically

neutral

Searching for displaced vertices

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General Selection

Background:

2015-10-27

arXiv:hep-ph/0605193

𝐷0

𝑍 0

PV

Energy : 3TeV GeV GeV ps rad, max. nm nm

track

Z axis

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Problems Low particle multiplicity in secondary vertices (displaced vertices) Too high for SV (distance from primary vertex) of background events,

comparing to HV events

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Multiplicity: SV & Particles from SV

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Low multiplicity - cut on Higgs

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0.8 rad <𝜃h<2.4 rad

Cut on choosing barrel Possibly better SV reconstruction in this region

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Low multiplicity - cut on Higgs

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No effect on particle multiplicity in SV

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Low multiplicity GeV & GeV

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GeV for each of b quarks or GeV for each of b quarks

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Secondary Vertices ,

for signal under background Peaks corresponding to detector material

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Cut on number of tracks in SV

𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒𝑠 𝑖𝑛𝑆𝑉 ≥ 4h𝑤𝑖𝑡 𝑜𝑢𝑡 𝑐𝑢𝑡

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Visible efffect, but it does not solve the problem

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Effects on SV Cut on number of tracks in SV

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h𝑤𝑖𝑡 𝑜𝑢𝑡 𝑐𝑢𝑡 𝑝𝑎𝑟𝑡𝑖𝑐𝑙𝑒𝑠 𝑖𝑛𝑆𝑉 ≥ 4

Significant difference after choosing higher particle multiplicity SV’s

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SV Pairing for (distance between SVs)

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For SV with multiplicity = 4: Selective pairing:

Sorting SVs by

First pair for minimum Nonselective pairing:

Paired all posibilities

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Dijet & Fourjet Mass

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Dijets: pairing two jets with similar masses Criterium : minimization of

Dijet Mass

Dijets Hidden Valley: only jets with > 50% particles from the same

Dijets background: all possible combinations.

Pairing two jets with similar masses

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Conclusions

2015-10-27

No sufficently effective solution for signal wrt PV Small effect applying cut on track multiplicity in SV

Currently no solution for low particle multiplicity in SV No effect when choosing barrel No effect applying cuts on b quarks

Significant difference in Dijet masses, when choosing different algorithm of jet pairing

Plans for the future: develop new algorithm for SV merging employing cone algorithm  look at direct HV production via Z'

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Thank you for your attention

2015-10-27