# Presentation: 237801

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- Chris Hays, Duke University

**CERN Non-SM Higgs Workshop**
**Dec 1-2, 2004**

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*H**++*
*H**+*
*H**0*

- Recent results

- Future analyses

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*H**++*
*H**+*
*H**0*

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## Why Higgs Triplets?

- Natural expansion of Higgs sector
- 	* frequently arise in models with 			additional gauge groups

- Little Higgs
- 	Increases scale of
- 	divergences by ~10

- Left-right symmetric  (SU(2)L x SU(2)R  x U(1)B-L x SU(3)c)
- 	Restore parity symmetry to weak force at scale *v**R*
- 	See-saw mechanism for light  masses

*Left-right model phenomenology well studied*
- 	* Excellent reference model for searches

- C. Hays, Duke University, Non-SM Higgs Workshop

## (     )

- Non-supersymmetric left-right models
- 	* Triplet masses typically proportional to *v**R*

-  Triplets could be observable at CDF
-  Simplest see-saw mechanism not valid
- 	(but could still apply:  e.g. add sterile neutrinos)

*If **v**R** ****1 TeV:*

-  Observable triplets requires scalar potential parameter tuning
-  See-saw mechanism applicable

*If **v**R** **≫****1 TeV:*

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*H**R**++*
*H**R**+*
*H**R**0*

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*H**L**++*
*H**L**+*
*H**L**0*

- C. Hays, Duke University, Non-SM Higgs Workshop

## Scenarios with Light Higgs Triplets

- Supersymmetric left-right models
- 	*  Require additional Higgs multiplets or higher-
- 		dimensional operators (HDO) in the superpotential
- 	*  HDO lead to light doubly-charged Higgs:  *m**H**±±* ****(*v**R*2/MPl)

- C. Hays, Duke University, Non-SM Higgs Workshop

*See-saw suggests **v**R** ~ 10**10** GeV, so m**H**±±** ~ 100 GeV*

*Gauge-mediated SUSY breaking:*
-   Light HR_++_

*Gravity-mediated SUSY breaking:*
-   Light HR_++_

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- Also:  HDO models require R-parity conservation

## Doubly Charged Higgs Search at CDF

- pp production cross section dominated by Z/ exchange
- 	*  Completely determined by weak coupling
- 	*  *W *Higgstrahlung cross section depends on *v**L*,

- C. Hays, Duke University, Non-SM Higgs Workshop

- constrained by the  parameter to be small

***(m**        **= 100 GeV) = 0.12 pb*

- Expect *H*_*++*_ to decay exclusively to leptons
-   *  No quark couplings due to charge conservation
-   *  *W*_*+*_*W*_*+*_ decay constrained by  parameter
*  **	**   **L**Y** = ih**ij**(****c**Li****2**H**L****Lj** + ****c**Ri****2**H**R****Rj**)*

*H**L**++*

*Violates lepton number;*
*new quantum number: B-L*

## Doubly Charged Higgs Search at CDF

- Search for H_++_ decays to *ee*, **, *e***
- 	*  Extremely clean signatures
- 	*  Only require one *ll'* pair/event
- 	*  Excellent discovery potential

- C. Hays, Duke University, Non-SM Higgs Workshop

- Low-mass background
- dominated by
- hadrons       leptons

- Use *m**ll'* < 80 GeV region to
- test background prediction

## Doubly Charged Higgs Search at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

- Test hadron      lepton predictions using low ET (<15 GeV)
- same-sign events with one lepton failing identification criteria

*Sample dominated by dijet events*

- Same sign *ee* channel complicated by
- bremstrahlung in silicon detector

- * Bremstrahlung can convert to two
- 	electrons, one of which has the
- 	opposite sign of the prompt electron
- ** Can result in wrong sign identification*

*Drell-Yan a significant background*
*Search only in region m**ee **> 100 GeV*

## Doubly Charged Higgs Search at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

*Luminosity and acceptance key to sensitivity*
**  <1 event background means cross section limit is directly **	**	**	**	**proportional to luminosity and acceptance*

- :  Trigger muon has limited || (<1),	 coverage, second muon has large 	coverage (|| < ~1.4, all ).

*ee*:  Both electrons have large  			coverage, but limited || (<1).  Falls 	rapidly for *m*<100 GeV due to cut-off

*e***:  Combination of limited electron 	and muon coverage reduces 			acceptance relative to *ee* and .

*L** ~ 240 pb-1:  Largest sample of any *
*published Tevatron result!*

*Very high acceptances!*

*Trigger and identification efficiencies included*

## Doubly Charged Higgs Search at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

- No events observed in signal regions

*Set 95% C.L. cross section x BR limits*

- Assuming exclusive decays to a given channel, set mass limits:
*H**L**±±**      ****:  m > 136 GeV*
*H**L**±±**      e****:  m > 115 GeV*
*H**L**±±**      ee:   m > 133 GeV*
*H**R**±±**      ****: m > 113 GeV*

- For diagonal couplings of equal magnitude, results correspond to the following approximate limit:
*H**L**±±**:  m > 120 GeV*

## Doubly Charged Higgs Search at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

- Mass limits highest in the world for *H**L**±±* in these channels
- 	* Sensitive to a wide range of Yukawa coupling values
- 10-5 < *h**ij* < 0.5

*Complementary to indirect searches*
*h**ij* limits for *m *= 100 GeV:
- Bhabha scattering:  *h**ee* < 0.05
- (g-2):  *h**** *< 0.25
-       3e:  *h**ee**h**e*** < 3.2 x 10-7
-       e:  *h****h**e*** < 2 x 10-6

*D. Acosta et al., *
*PRL 93 (2004), 221802*

## Doubly Charged Higgs Search at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

- CDF has also searched for quasi-stable H±±
- 	* Probes low Yukawa coupling values
-  *h**ij* < 10-8

- Strategy:
*  **Use dE/dx information from tracker*
*  **Search for pairs of high-momentum *
*	**doubly-charged tracks*
*  **Define tight “discovery” selection *
*	**including calorimeter ionization *

*Couplings don't exist for *
*additional triplets *
*that conserve lepton number*

## Doubly Charged Higgs Search at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

- dE/dx resolution provides many  separation of signal and background

- Background < 10-5
*  **Single-event discovery!*
- Signal confirmation defined *a priori*
*  **Require large MIP energy in calorimeter*
*  **Further suppresses muon backgrounds*

*Backgrounds studied with data and MC*

- < 10-6

- < 10-6

- < 10-9

- < 10-5

- < 10-12

- < 10-7

- < 10-9

- < 10-6

*No candidates in samples used to*
*determine acceptance*
*Yields upper limits on expected *
*background*

*Calibration sample*

*Expected *
*signal*

*Background*

## Doubly Charged Higgs Search at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

- Acceptance has additional inefficiencies and uncertainties (beyond )
- *  Fraction of H±± with  too small to reconstruct tracks
- *  Multiple scattering affecting track matching to muon track segment
- *  Ionization affecting calorimeter isolation requirements

*Acceptance reduced relative to ****:*
**  Both H**±±**  must be central, with *
*	**reconstructed tracks*
**  Additional track cuts and *
*	**inefficiencies *
**  Still > 30%*

*L** ~ 200 pb-1*

## Doubly Charged Higgs Search at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

- No events observed in data

*Set 95% C.L. cross section limit*

- Infer mass limits:
*H**L**±±**:  m > ~125 GeV*
*H**R**±±**:  m > ~100 GeV*

- Limits similar to  and *ee* decay channels
*Sensitivity will improve with order of magnitude increase in luminosity: *
*H**L**±±**:  m ~ 200 GeV*
*H**R**±±**:  m ~ 170 GeV*

- Left and right cross
- sections combined

## Ongoing H±± Search at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

*Same-sign tau decays*

- Experimentally challenging:
- * Cannot fully reconstruct invariant mass
- * Hadronic tau decays difficult to detect

- Many problems solved in *H**0*     search:

*Studying issues of sign *
*identification*
*Determining backgrounds for *
*same-sign sample*

- Phenomenologically interesting:
- * *h*** coupling the least constrained

## Other Possible Triplet Searches at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

- Same final state as *H**0*    *WW* search

*Can reoptimize for leptons *
*from H**±** decays*
*NLO cross section would help*
*in full analysis*

*H**±*:
- * Experimentally accessible
- * No quark couplings if no mixing with Higgs doublet

## Other Possible Triplet Searches at CDF

- C. Hays, Duke University, Non-SM Higgs Workshop

*H**±±*, *H**±*:
- * Existing searches have sensitivity
- * Signatures depend on NLSP

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***1**0*: *H**±±**     ll'     l****1**0**l'     l****0****0**l' **	**	**H**±**     l****     l****1**0****    l****0****0**** *
*	**Final state lll'l'****E**T****Final state ll****E**T**	*
*l*: *H**±±**     ll'     l****0**l'**	**	**	**	**	**	**H**±**     l****     l****0***
*	**Final state lll'l'E**T**	**	**	**	**	**Final state llE**T*

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*Need to validate MC generators, *
*use for optimization and*
*acceptance determination*
*NLO cross section would help*

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## Summary

- C. Hays, Duke University, Non-SM Higgs Workshop

*Higgs triplets a likely component of non-SM Higgs sector*
-   Arise in well-motivated models
*Doubly-charged Higgs searches particularly attractive*
-   Accessible to colliders in a number of scenarios
-   Extremely clean signatures:  excellent discovery potential
*CDF has world's highest mass limits for long-lived H**±±** and decays to ee, e****, ***
-   Ongoing data-taking will significantly extend sensitivity
-   Still early in Run 2!
*Potential for a range of additional triplet searches*
-   Need to determine sensitivity (cross sections, acceptances)