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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