Beyond

the Standard Model

at HERA II

Hubert Spiesberger

DESY Forum

14.5.2002

� High luminosity and polarization . . .

� tests of the electroweak interactions

� future searches, mainly:

� supersymmetry

� production processes and decays

� signatures and generic searches

� model scenarios: 6Rp MSSM, GMSB

HERA II upgrade

� Luminosityfocussing magnets inside detector! L increased by factor � 3:5expect

RdtL ' 1000 pb�1 till 2006

) high precision for NC / CC DIS cross sections,structure functions, parton distributions

) small cross sections of rare processes accessible

� Polarizationspin rotators and polarimetry,degree of polarization up to PL = 0:7

) test helicity structure of electroweak interactions

) diagnostic tool for new physics

� Detector upgradesvertex, tracking, luminosity system

2

Electroweak tests

Example: charged current DIS cross sectionquantify agreement of data with SM by W -mass

(strategies for a determination of mW )

d�

dQ2

�����CC

=1�

Q2+m2W

�2�(x;Q2) (1)

" pdf;normalization

=1�

Q2+m2W

�2 G2�m4W

2��0(x;Q2) (2)

l G� ! GSM�at tree-level

=1�

Q2+m2W

�2 ��2

4�1�m2

W=m2Z

�2�00(x;Q2)

(3)

=1�

Q2+m2W

�2 ��2

4s4W�000(x;Q2)� (4)

�1�loopCC (�;mZ ;mW ;mt;mH ; : : :)

�1�loopCC takes account of one-loop electroweakradiative corrections

SM predictions are function of a set of independentparameters, e.g. �, mW , mZ, mtop, mHiggs, : : :

3

mW determination: propagator mass

2-parameter �t: G� and mW

0.9

0.95

1

1.05

1.1

74 76 78 80 82 84 GeV

H1

SM

ZEUS

combined

Mprop

stat. errors only

(GC

C/G

F)2

E. Elsen, Tampere '99

constrained �t, �xing G�:

mW = 79:9� 2:2stat � 0:9sys � 2:1pdf (e�p)

mW = 80:9� 3:3stat � 1:7sys � 3:7pdf (e+p)

4

W

79.0

79.5

80.0

80.5

81.0

81.5

0 50 100 150 200 250 300

mW

mt

CC250 pb-1

CC + NC1000 pb-1

CC + NC1000 pb-1 andσ(mt) = 5 GeV

1% systematics

GeV

GeV

Gµ(mH=100 GeV)

Gµ(mH=800 GeV)

constrained �t:

insert

G� = GSM� (mW ;mt)

e�pPL = �0:7

high-Q2 NC/CC

HERA data

combined with

direct mtop

G� constraint

(CC at Q2 = 0)

δmW

0

100

200

300

400

500

0% 5%

CC

250 pb-1

NCMeV

1000pb-1

Systematic

uncertainty

e�p

PL = �0:7

Beware: in case of a disagreement with other mea-surements ! need to convince that no large syste-matic e�ects are responsible

5

Electroweak tests

Example: utilizing polarized beams

Charged current:

� / (1� PL)

! easy straight-line �ts,! limits on right-handed currents (mWR

)

Neutral current:

d2��

dxdQ2= ~��0 + PL~�

�L

��0 and ��L are functions of lepton and quark coup-ling constants gV , gA

Q2 (GeV 2)

(d2 σ/

dxdQ

2 ) / (

d2 σ em /d

xdQ

2 )

e-L

e-R

e+L

e+R

a)

Q2 (GeV 2)

(d2 σ/

dxdQ

2 ) pb

/GeV

2

b)

0

0.5

1

1.5

2

2.5

3

10 102

103

104

105

10-4

10-3

10-2

10-1

1

103

104

6

NC coupling constants

with 250 pb�1 / beam e�L , e�R, e

+L , e

+R

(assume pdf's known to within < 5% unc.)4-parameter �t to quark coupling constants !

vu : 13%; vd : 17%

au : 6%; ad : 17%

2-parameter �ts

0.15

0.175

0.2

0.225

0.25

0.45 0.5 0.55au

v u

-0.5

-0.4

-0.3

-0.2

-0.6 -0.4ad

v d

(a)

P = 0

P = 0.2

P = 0.5

P = 0.7(b)

�xedvd, ad

�xedvu, au

-0.36

-0.34

-0.32

-0.3

-0.54 -0.52 -0.5 -0.48

gAb

g Vb

Preliminary

68.3 95.5 99.5 % CL

SM

0.16

0.18

0.2

0.22

0.47 0.5 0.53

gAc

g Vc

Preliminary

68.3 95.5 99.5 % CL

SM

LEP results

for b-quarksfor c-quarks

LEPEWWG winter 2002 7

Rare SM processes

� W production! anomalous WW couplings ��, �see Proc. Future Physics at HERA '96

� Z production

� Lepton pair productionfrom various mechanismssee Proc. Future Physics HERA '96, DIS2002

� Radiative processesep! +X in NC, CC

) Background for non-SM physics

8

Search for new physics

see Proc. Physics at HERA '91

and Future Physics at HERA '96

� Contact interactions

� Extra Z0, W

� Heavy Majorana neutrinos, WR

� Excited fermions (leptons, neutrinos, quarks;substructure)

� Large extra dimensions

� Doubly charged Higgs

� Light gluinos

� Leptoquarks

� Lepton avor violation

� Supersymmetry (various model scenarios)

9

�

`i `j

qr qs

HERA,NuTeV, . . .`N ! `0X

)

e.g. LEPe+e� ! hadr

+

Tevatronp�p! `+`�X

*

LCI =Xi;j;r;s

4���ABijrs

�2�ijrs��i�

A`j� ��qr�

Bqs�

with i; j; r; s denoting avor and L;R and �A = �, � 5

Gilmore '96

10

Future: leptoquarks

Improved limits fromhigher luminosity

Virey '98

if there is an e�ect ! polarization may help todistinguish di�erent types of leptoquarks

Virey et al '99

11

Search for supersymmetry

production processes

� eq ! ~e~q e ~e;~�

q ~q

~�0;�i

� eq ! ~�~q0L

� eq ! ~e~�0i q e

q q

; Z

~e; ~�

~�0i ; ~��

i

e

q q

; Z

~e;~�

~�0i ; ~��

i

eq ! ~�~��i q

� eq ! e~q~�0ieq ! e~q0~��i

� g ! ~t~t

with Rp violation also resonant production

� eq ! ~q e

qk

~qi�01ik

polarization:

only e�L , e+R

12

Search for supersymmetry

decays ! signatures

~q ! eq with 6Rp~qL ! q~�0i ; q0~��i ~eL ! e~�0i ; �~��i~qR ! q~�0i ~eR ! e~�0i

heavier ~�0;� cascading to

~�0i ! f �f ~�0i�1; f �f 0~��j

~��i ! f �f 0~�0j

MSSM: lightest supersymmetric particle (LSP)

~�01 is stable

MSSM+ 6Rp: LSP decays with Rp violation

~�01 ! e�u�d; e+d�u; �d�d

~�+1 ! e+d�d; �u�dvia �0111

) signatures are combinations of

6ET , `�, jets

maybe also � , , Z (= `+`�), W (= `�), b- andc-jets

13

Generic search ?

motivation: very time-consuming to perform dedi-cated searches for every speci�c modelmay overlook the unexpected new

problem: if a number of outstanding, seeminglyatypical events is found: how to evaluate unbiasedstatistical signi�cance?

example: SLEUTH, see D0: hep-ex/0006011

� choose set of �nal states (composed of objects6ET , `�, , jets, . . . )

� choose kinematical variables (like 6ET , pT 's)� de�ne regions about data points (after variabletransformation to obtain uniform background)

� calculate probabilities of background uctua-ting up to (or above) the observed number ofevents

� �nd interesting regions

� interpretation: badly modeled background ornew physics

requires precise SM predictions including higher-order corrections

14

Deriving limits

measurements provide limits on � �B

interpretation within speci�c models

e.g. MSSM: �B(~m) �! mass limits

e.g. MSSM + 6Rp: �B(~m;�0) �! exclusion plotsmass vs. coupling

(depending on additional parameters)

e.g. mSUGRA with REWSB, independent parame-ters: m0, m1=2, sign�, tan�, (�

0ijk)

�B(m0;m1=2; tan�; �0) �! exclusion plots

e.g. m0 vs. m1=2(with tan � and �0 as parameters)

other models ?

15

MSSM: mass limits

Schleper, '96: eq ! ~e~q

100pb-1

LEP1

100pb-1

500pb-1

(M e + M q) / 2 (GeV)

M2

(G

eV)

tanβ=1.41

µ=-300GeV

0

20

40

60

80

100

120

140

0 20 40 60 80 100

compare recent limits from LEP2

ALEPH, hep-ex/0112011:

20

40

60

80

100

50 60 70 80 90 100Selectron mass (GeV/c2)

Neu

tral

ino

mas

s (G

eV/c

2 )

SelectronsALEPH

tan β = 2µ = -200 GeV/c2

Excluded at 95% CL

ObservedExpected

~e�R ! e�~�01

~e�R : m > 95 GeV

~��R : m > 88 GeV

~��R : m > 79 GeV

16

Supersymmetry with Rp violation

Motivation: consider fermion mass generation inthe MSSM

Yukawa superpotential

WY = �EijHLiEcj + �DijHQiD

cj + �Uij �HQiU

cj + �H �H

with super�elds L!

��LeL

�, H !

�H0

H�

�+ superpartners

L and H have same weak isospin and hypercharge! additional term suggested

W6Rp= �ijkLiLjE

ck+ �0ijkLiQjD

ck+ �00ijkD

ciD

cjUk+ �0HL

" " "lepton number baryon numberviolation violation

�00 = 0 avoids p decay

Analogy WY $W6Rpmay even suggest relation bet-

ween coupling constants ?

�0ijk = �0i �Djk with �0i = O(1) (5)

avor alignment

17

Consequences of Rp violation

) neutrino masses radiatively generated

�i �jbL bR��~qR ~qL

� �

mass matrix (m�)ij = mD� �

0i�0j

with mD� from loop factor, / 1=m2

~q

framework for �-mixing and �-masses

) allows resonant squark production at HERA

e�L�dk ! �~u

jL; e+R d

k ! ~ujL

e�Luj ! ~dkR; e+R �u

j ! �~dkR

via �01jk

framework for leptoquarks with masses at the elec-troweak scale

) generates lepton- avor violatione

qk

~qi

�01ik �0`ij

`

qj

! Pk�0

1ik�0

`ij

~m2i

may also exploit relation to �Dij : CKM quark mixing

18

Rp violation: the LLE-term

Kon et al., hep-ph/0203262

consider LLE-term with �231 6= 0contains e� �� ~�� couplingbound from � decay: �231 < 0:07 for m~eR

= 100GeV

) sneutrino production at HERA

e

q q

; Z

�

~��

e ��231

e�p! �~��X

with

~�� ! e�

e

q q

; Z

�~��

��231�

�nal state: �+��e�

cross section: O(10) fb, BR ' 1 for large M2, �SM-background mainly 2 and ; Z production

0.1

1

10

Eve

nts

per

bin

1208040

M(e-µ+

) (GeV)

6

80.1

2

4

6

81

2

4

6

810

Eve

nts

per

bin

12080400

M(µ+µ−) (GeV)

SM expectation RB+SM events

19

g p y y g

� super-Higgs mechanism active insecluded sector(broken local supersymmetry! Goldstino-gravitinoorder parameter (vev) of SB: F

� coupled to messenger sector with N generati-ons of �elds with Susy mass / Mm

� gauge interactions transfer Susy breaking toobservable sector

model parameters:

� � = F=Mm

� N

� Mm

� tan�, sign�

� CG: Goldstino coupling

~X

X

~G

�( ~X ! X ~G) =�m5

~X

16�(CGF)2

0@1� m2

X

m2~X

1A4

(�: model-dependent mixing parameter)

mass of Goldstino: m ~G = F=p3MPlanck very small

) LSP is Goldstino-gravitinoNLSP is relevant for accelerator physics

20

examples (\model lines") see e.g. hep-ex/0008070

� neutralino NLSP: ~�01 = ~ =~Z or ~h

~�01 ! ( ; Z; h) + ~G

� slepton NLSP (maybe stau):

~! `+ ~G

� squark NLSP:~q ! q+ ~G

for stop with m~t < mt: ~t! bW + ~G

� gluino NLSP:~g ! g+ ~G

phenomenology and signatures classi�ed by decaylength:

c� '�100�m

�

� 100GeV

m ~X

!5 pF

100TeV

!40@1� m2X

m2~X

1A�4

� prompt decay: c� smallvarious signatures with 6ET , , `�, jetsspectrum usually harder than in conventionalscenarios since ~G is essentially massless

� macroscopic decay length: �m < c� < few mdecay inside detectorsignatures with displaced vertices, tracks withkinks

� decay outside detector: c� � mif NSLP is neutralino: conventional 6ET signa-tureotherwise: heavy stable charged particles

21

GMSB new signatures

� photons

� displaced vertices, tracks with kinks

� heavy stable charged particles

GMSB limits

searches at LEP2 and Tevatron

for example:

e+e� ! ~+~� with slepton NLSP

prompt decays to �nal states with 2, 4 or 6 leptonsand 6ET ; displaced vertex; stable sleptons (indepen-dent of �( ~G))

m~e > 66 GeV

m~� > 95:2 GeV

m~� > 86:1 GeV

ADLO prel. (De Filippis, DIS2002)

not (yet) studied for HERA

can HERA be competitive?

22

Summary

� Tests of the electroweak interactionsat large Q2: W mass and neutral current quarkcouplings

� Improved limits from higher luminosity

� Polarization as a diagnostic tool for new physics

� Searches for supersymmetry

� Generic searches ?

� Rp violation: LQD and LLE terms

� New signatures from GMSB ?

Maybe there is more physics

Beyond the Standard Model

at HERA II ?

23